Cancer associated macrophage-like cells in metastatic renal cell carcinoma predicts for poor prognosis and tracks treatment response in real time

Renal Cell Carcinoma (RCC) is a fatal urological cancer, with one third of patients diagnosed with metastasis, resulting in a 5-year survival of only 12%. Recent advancements in therapies have increased survival in mRCC, but lack efficacy in subtypes, due to treatment resistance and toxic side effects. Currently, white blood cells, hemoglobin, and platelets are limitedly used as blood based biomarkers to help determine RCC prognosis. Cancer associated macrophage-like cells (CAMLs) are a potential mRCC biomarker which have been identified in peripheral blood of patients with malignant tumors and have been shown to predict poor clinical patient outcomes based on their number and size. In this study, blood samples from 40 RCC patients were obtained to evaluate the clinical utility of CAMLs. CAML changes were monitored during treatment regimens to evaluate their ability to predict treatment efficacy. It was observed that patients with smaller CAMLs had better progression free survival (HR = 2.84, 95% CI 1.22-6.60, p = 0.0273) and overall survival (HR = 3.95, 95% CI 1.45-10.78, p = 0.0154) versus patients with larger CAMLs. These findings suggest that CAMLs can be used as a diagnostic, prognostic, and predictive biomarker for patients with RCC which may help improve management of advanced RCC.

Abstract 3310: Extracellular vesicles budding from stromal macrophages in the blood of metastatic non-small cell lung cancer patients correlates with poor survival

Purpose: Cancer extracellular vesicles (EVs) are involved in cellular communication, tumor growth, progression, and metastasis in cancer. The origins of EVs, their formation, and potential clinical use as biomarkers are not well understood. Recently, budding of extracellular structures on Cancer Associated Macrophage-Like Cells [CAMLs] a specific subtype of phagocytic circulating stromal cells has been observed in metastatic non-small cell lung carcinoma (mNSCLC) patients. In this prospective analysis of n=40 mNSCLC samples, we enumerated EV budding on CAMLs to determine if their formation had an effect on clinical outcomes. These preliminary results suggest that EV budding from a specific subtype of circulating tumor associated macrophage prognosticates for worse clinical outcome which may serve as the mechanism for cancer EV formation and spread throughout the body.

Patients and Methods: We initiated a single blind prospective pilot study to evaluate extracellular budding on the CAMLs of mNSCLC patients from blood samples obtained prior to therapy to determine their prevalence and clinical utility. Anonymized blood was procured and filtered to isolate CAMLs and stained for cytokeratin, CD45, CD31 and PD-L1. EV budding was observed as small (≤1 µm) bulbous protrusions from the cell periphery. EVs were quantified and compared against patient progression free survival (PFS) and overall survival (OS) with hazard ratios (HRs) at 24 months by censored univariate analysis. The imaged EVs were also characterized by their PD-L1 biomarker expression.

Results: CAMLs were identified in 88% (n=35/40) of all samples, with EV budding identified in 60% (n=21/35) of CAMLs. These EVs appeared with tumor positive proteins (i.e. CD31, CD45, PD-L1 and cytokeratin). With a minimum of 24 months of follow-up, it was determined that the presence of EV budding in patients’ CAMLs was associated with significantly worse PFS (HR=4.00, 95%CI=1.4-12, p=0.0251) and borderline significant OS (HR=3.57, 95%CI=1.1-12, p=0.0747).

Conclusions: EV budding found on phagocytic stromal cells found in the blood appear with tumor positive biomarkers and predict poor survival. These findings suggest that CAMLs are an origin cell for some cancer EVs. Larger validation studies and cross comparison of PD-L1 on EVs as it related to immunotherapy response is ongoing.

Citation Format: Jillian A. Moran, Steven H. Lin, Martin J. Edelman, Pablo Lopez, Jianzhong He, Yawei Qiao, Ting Xu, Zhongxing Liao, Kirby P. Gardner, Cha-Mei Tang, Daniel L. Adams. Extracellular vesicles budding from stromal macrophages in the blood of metastatic non-small cell lung cancer patients correlates with poor survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3310.

Abstract P1-05-28: Decreases in Circulating Tumor Associated Cells Predicts PFS and OS In A Pooled Analysis Of Phase I Clinical Trials Using SV-BR-1-GM Therapy With Or Without Immune Check-Point Inhibitors In Metastatic Breast Cancer Patients

Background: In metastatic Breast Cancer (mBC), Circulating Tumor Cells (CTCs) are clinical indicators of worse prognosis and indicate patients (pts) not responding to current therapy. However CTCs are rare, found in < 20% of mBC pts, and many pts without CTCs may also progress. Recently an inflammatory pro-tumorigenic PD-L1 expressing macrophage (Cancer associated macrophage-like cell [CAML])was identified in the blood, which was found in >90% of mBC pts and may indicate tumor response to new therapies (JCO 40[16_Suppl] 2022). SV-BR-1-GM is a mBC cell line derived with antigen presenting characteristics was developed for treatment of mBC as a monotherapy (monoTx), or in combination with checkpoint inhibitors (comboTx). We report preliminary post-hoc results of a pooled analysis of n=18 monoTx mBCs pts and interim results of n=15 comboTx to analyze the predictive value of CTCs & CAMLs, as well as CAML PD-L1 expression, isolated from pt peripheral blood pre & post treatment to predict drug response, with end point outcomes of Progression Free Survival (PFS) and Overall Survival (OS) at 24 months. Methods: The SV-BR-1-GM regimen includes low pre-dose cyclophosphamide, intradermal inoculation of ~20 million irradiated SV-BR-1-GM cells and post-dose local interferon-α with cycles every 2 weeks x 3, then monthly. ComboTx adds an anti-PD-1 antibody with cycles every 3 weeks. Blinded blood samples were taken at baseline (BL), prior to starting SV-BR-1-GM therapy (n=33), and a 2nd sample (T1) taken after therapy initiation (~52 days) obtained as part of the exploratory portion of 2 prospective phase I clinical drug studies, NCT03066947 & NCT03328026, to evaluate the predictive value of CTCs/CAMLs and CAML PD-L1 measured by LifeTracDx liquid biopsy. The quantities of CTCs & CAMLs were analyzed based on PFS using RECIST v1.1 and OS hazard ratios (HRs) by censored univariate analysis at 24 months. Results: A total of 33 mBC pts were pooled from monoTx (n=18), or comboTx (n =15), all with available blood samples at BL. CTCs were found in 30% (n=10/33) of pts at BL, and CAMLs were found in 94% (n=31/33) at BL. Presence of CTCs at BL did not correlate with worse PFS (HR=1.0, p=0.8550), but did trend for pts with worse survival (HR=5.1, p=0.0641). T1 samples were available from 61% (n=20/33) pts. A drop in CAMLs or CTCs after treatment at T1 was observed in 50% of pts, which correlated with a significantly improved PFS HR=11.8, p=0.0019 and OS HR=226.3, p=0.0397. Overall, pts with a decrease in CTCs/CAMLs after induction of SV-BR-1-GM therapy had a ~350% improvement in median PFS (1.9 mo. vs 6.6 mo.) and a ~200% improvement in median OS (6.3 mo. vs 12.4 mo). When stratified between monoTx and comboTx, pts with a decrease in CTCs/CAMLs had an improved PFS (HR 11.9, p=0.0136) in the monoTx group and an improved PFS (HR 17.5, p=0.0017) in the comboTx group. Further, while expression of CAML PDL1 at BL was not correlated with improved PFS (HR=1.0, p=0.9078), CAML PD-L1 expression at BL was correlated with significantly better OS HR=9.5, p=0.0116, consistent with long term benefit of SV-BR-1-GM therapy in this group of pts. Conclusions: We observed that treatment with the SV-BR-1-GM regimen was associated with decreases in the presence of CTCs and CAMLs in 50% of patients, which also significantly correlated with ~350% better median PFS and ~200% better median OS within 2 years. SV-BR-1-GM therapy alone, or as a combination treatment with anti-PD-1, appears to have improved long term clinical outcomes in a large portion of heavily pre-treated mBC patients compared to other typical standard of care published results.

Citation Format: Daniel Adams, Mingjin Chang, Miguel Lopez-Lago, Cha-Mei Tang, William Williams, Giuseppe Del Priore. Decreases in Circulating Tumor Associated Cells Predicts PFS and OS In A Pooled Analysis Of Phase I Clinical Trials Using SV-BR-1-GM Therapy With Or Without Immune Check-Point Inhibitors In Metastatic Breast Cancer Patients [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-28.

Monitoring PD-L1 Expression on Circulating Tumor-Associated Cells in Recurrent Metastatic Non-Small-Cell Lung Carcinoma Predicts Response to Immunotherapy With Radiation Therapy

PURPOSE

Current diagnostic methods to determine programmed death 1 (PD-1) receptor and its ligand (PD-L1)/PD-1 immunotherapy (immune checkpoint inhibitor [ICI]) efficacy in recurrent or metastatic non-small-cell lung carcinoma (rmNSCLC) are imprecise. Although previously shown that patients with high tumor PD-L1 (≥ 50%) demonstrate clinical benefit in the form of disease reduction and improved survival, patients with low PD-L1 (< 50%) sometimes benefit from treatment. Since the PD-L1/PD-1 pathway is dynamic, monitoring PD-L1 levels during treatment may be more accurate than a static baseline tumor biopsy; however, rebiopsying the primary or metastatic disease is rarely feasible. Liquid biopsies that measure the upregulation of PD-L1 on tumor-associated cells (TACs), ie, cancer-associated macrophage-like cells and circulating tumor cells, have been performed, but their predictive value for ICI therapy efficacy is unknown.

MATERIALS AND METHODS

We initiated a single-blind prospective study to evaluate TAC PD-L1 expression changes in rmNSCLC from blood samples before (T0) and after (T1) treatment with ICI (ICI, n = 41) or without ICI (no ICI, n = 41). Anonymized blood was filtered to isolate TACs, which were then quantified for high/low PD-L1 expression. Progression-free survival (PFS) or overall survival (OS) hazard ratios (HRs) were evaluated at 18 and 24 months by censored univariate analysis.

RESULTS

Increased TAC PD-L1 expression between T0 and T1 in patients who were not treated with ICI had no relationship with PFS or OS. However, increased TAC PD-L1 expression between T0 and T1 in patients treated with ICI had significantly better PFS (HR, 3.49; 95% CI, 1.5 to 8.3; P = .0091) and OS (HR, 3.058; 95% CI, 1.2 to 7.9; P = .0410).

CONCLUSION

Blood-based monitoring of dynamic changes in PD-L1 in TACs appears to identify patients with rmNSCLC who may benefit from ICI.

Freestanding high-aspect-ratio gold masks for low-energy, phase-based x-ray microscopy

High-resolution, x-ray phase contrast microscopy, a key technique with promising potential in biomedical imaging and diagnostics, is based on narrow-slit high-aspect-ratio gold gratings. We present the development, fabrication details, and experimental testing of the freestanding 10μm thick gold membrane masks with an array of 0.9-1.5μm void slit apertures for a novel low-energy x-ray microscope. The overall mask size is 4 mm × 4 mm, with a grating pitch of 7.5μm, 6.0-6.6μm wide gold bars are supported by 3μm wide crosslinks at 400μm intervals. The fabrication process is based on gold electroplating into a silicon mold coated with various thin films to form a voltage barrier, plating base, and sacrificial layer, followed by the mold removal to obtain the freestanding gold membrane with void slit apertures. We discuss key aspects for the materials and processes, including gold structures homogeneity, residual stresses, and prevention of collapsing of the grid elements. We further demonstrate the possibility to obtain high-resolution, high contrast 2D images of biological samples using an incoherent, rotating anode x-ray tube.

Safety, efficacy, and clinical outcomes of the anti-CCR5 inhibitor (Leronlimab): A pooled analysis of three clinical trials in patients with mTNBC

e13062

Background: Metastatic triple negative breast cancer (mTNBC) is a highly invasive BC subtype with limited treatment options and poor clinical outcomes. Leronlimab, a humanized IgG4κ antibody, competitively inhibits CCR5, a cancer motility receptor and target for cancer inhibition. We report on a pooled analysis of n = 28 mTNBC patients (pts) showing that leronlimab has potent antitumor activity with improved 1 year progression free (PFS) & overall survival (OS) with few treatment emergent adverse events (TEAEs). Further, we explored the effect of leronlimab on circulating tumor associated cells (TACs) from peripheral blood as a surrogate and early predictor of drug response. Methods: mTNBC pts results from 3 blinded prospective clinical drug studies, Phase 1b/2 dose escalation (NCT03838367), Compassionate Use (NCT04313075), and Basket Study (NCT04504942) were pooled to evaluate leronlimab’s safety & efficacy at 12 months (mos). Pts received ≥1 dose of leronlimab alone (n = 2), with carboplatin (n = 11) or with physician’s choice (n = 15). Pts received 1-33 doses, ranging from 350mg (n = 9), 525mg (n = 16) or 700mg (n = 3). In addition, anonymized pt peripheral blood was procured before and after (̃30 days) induction as an exploratory biomarker, to evaluate TACs in predicting efficacy. Progressive disease, stable disease or partial response was determined by RESICT v1.1, and univariate analysis was used evaluate PFS & OS. Results: mTNBC pts were pooled from Phase 1b/2 (n = 10), Compassionate Use (n = 16), and Basket Study (n = 2) treated with 350-700mg doses, 4 pts escalating 350 to 525mg. Pts had 1-5+ prior systemic therapies for mTNBC (median = 2), median age 52 (range 33-84), ECOG 0 (n = 18) or ECOG 1 (n = 10), n = 17 had visceral mets, and n = 6 had brain mets. A total of n = 68 TEAEs were reported, with n = 7 grade I/II & n = 1 grade III related to leronlimab. At 12 mos, pts had a mPFS = 3.8 mos (95%CI 2.3-6.2) and mOS = 6.6 mos (CI95% 4.9-12+). However, pts treated with 525-700 mg doses (n = 19) had a > 75% improved mPFS = 6.1 mos (95%CI 2.3-7.5) and mOS 12+ mos (95%CI 5.5-12+). Further, a drop in circulating TACs was identified in 75% (n = 21/28) pts and predicted for significantly better clinical outcomes, mPFS = 6.2 and mOS > 12 mos. Conclusions: These studies suggest that mTNBC pts dosed with leronlimab had high clinical benefit, i.e. longer PFS & OS with few TEAEs, and leronlimab resulted in a drop in circulating TACs in the majority of pts correlating with early therapy response. Clinical trial information: NCT03838367, NCT04313075, NCT04504942.

Monitoring PD-L1 expression on circulating stromal cells in blood predicts PFS and OS in patients with metastatic NSCLC treated with PD-L1/PD-1 immunotherapy

8535

Background: Cancer Associated Macrophage Like cells (CAMLs), a circulating stromal cell found in cancer patients (pts) blood, are phagocytic giant macrophages that appear to parallel the inflammatory PD-L1 state of the tumor microenvironment. Previously, we demonstrated in local non-small cell lung carcinoma (NSCLC), CAML PD-L1 expression is dynamic and predicts response to PD-L1/PD-1 immunotherapies (IMTs) following sequential sampling before and after chemotherapy (chemo) induction (̃30days) based on progression free (PFS) & overall survival (OS). However this has not been tested in metastatic NSCLC (mNSCLC). Here,we report the results of monitoring PD-L1 expression in CAMLs before and after chemo induction (̃30 days) to evaluate its predictive value in mNSCLC pts treated with or without IMT. Methods: A single blind multi-year prospective study was undertaken to test the relationship of PD-L1 expression in CAMLs to PFS & OS, pre & post chemo induction, in recurrent mNSCLC with (n = 41) or without (n = 41) additional anti-PD-L1/PD-1 IMTs. This included three IMTs: atezolizumab (n = 4), nivolumab (n = 8) or pembrolizumab (n = 29). We recruited 82 pts with pathologically confirmed recurrent mNSCLC prior to treatment for newly recurrent metastatic disease. Blood samples (15 mL) were taken at Baseline (BL), prior to chemo, and ̃30 days after chemotherapy (T1). Blood was filtered by CellSieve filtration & CAMLs’ expression scored as a binary high/low, to evaluate PFS & OS hazard ratios (HRs) by censored univariate & multivariate analysis at 18 months. Results: CAMLs were found in 97% of all tested samples, 94% at BL & 100% at T1. CAML PD-L1 at BL was found not to be associated with PFS or OS in pts treated with chemo alone (PFS p = 0.620 & OS p = 0.673) or chemo+IMT (PFS p = 0.353 & OS = 0.477) at 18 months. At T1, high CAML PD-L1 in pts treated with chemo alone had no significantly different PFS (HR = 1.3, p = 0.694) or OS (HR = 1.6 p = 0.503). However, high CAML PD-L1 at T1 in pts treated with chemo+IMT had significantly better PFS (HR = 3.1, 95%CI = 1.3-7.3, p = 0.019), and OS (HR = 3.4, 95%CI = 1.4-8.3, p = 0.014). Further subtyping & analysis is ongoing to evaluate PFS and OS at 24 months. Conclusions: Our data suggests that in mNSCLC, PD-L1 expression in circulating CAMLs dynamically upregulates after induction with chemotherapy and appears to predict patients with increased benefit to PD-L1/PD-1 IMTs, though additional studies are needed to validate these findings.

Tracking changes in circulating stromal cells and circulating tumor cells predicts responsiveness of new line induction in metastatic breast cancer after 1 cycle of therapy

3056

Background: In metastatic Breast Cancer (mBC), Circulating Tumor Cells (CTCs) are established prognostic indicators of patients (pts) not responding to new lines of therapy and who have poor clinical outcomes. However, CTCs are typically found in < 20% of mBC pts and many pts without CTCs will also progress. Recently an inflammatory pro-tumorigenic macrophage emanating from tumor stroma (i.e. Cancer associated macrophage-like cell [CAML]) was found in > 90% of mBC pts and were also indicative of poor clinical outcomes. As CTCs & CAMLs are isolated in conjunction from a single blood sample, and both are prognostic for therapy response, we evaluated CTCs & CAMLs before and after initiation of new therapies in mBC to determine their combined prognostic/predictive values. Methods: An observational prospective 2-year multi-institutional study was undertaken to evaluate CTCs & CAMLs before, and after, induction of any new line of therapy in pts with diagnosed mBC (n = 101). Anonymized and blinded blood samples were taken at baseline (BL), prior to starting a new systemic therapy, and a 2nd sample (T1) taken after therapy initiation (̃30 days). Blood was filtered by CellSieve filtration. The quantities and subtypes of CTCs & CAMLs were analyzed based on RECIST v1.1 for progression-free survival (PFS) and overall survival (OS) hazard ratios (HRs) by censored univariate & multivariate analysis at 2 years. Results: CTCs were identified in 35% (n = 35/101) of pts at BL & 24% (n = 24/101) at T1, with a single CTC at T1 being highly prognostic for worse PFS HR = 6.2 95%CI 3.0-13.2, p < 0.001 & OS (HR = 5.1 95%CI 2.0-13.4, p = 0.002. In parallel, CAMLs were found in 93% of BL and 86% of T1 samples, and whose decreases were significantly prognostic for improved PFS (HR = 2.7, 95%CI 1.4-5.1, p = 0.006) and OS (HR = 4.4 95%CI 1.5-13.2, p = 0.018) when CTCs were absent. Overall ≥1 CTC at T1 (n = 24) had median PFS = 2.4 & mOS = 4.8 months (mos), however, in pts without CTCs plus an increase in CAMLs (n = 36) had mPFS = 5.9 & mOS = 14.1 mos, while in pts without CTCs plus a decrease in CAMLs (n = 41) had mPFS = 14.8 & mOS = 18.8 mos. Conclusions: Our data confirms that pts with persistent CTCs have the worst clinical outcomes. Further, simultaneous CAML quantification provided a new dynamic predictive blood based biomarker in pts without detectable CTCs which may be useful to better individualize therapy and improve outcomes, though future studies are need to validate these findings.

Monitoring engorgement of phagocytic circulating stromal cells during chemo-radiotherapy induction predicts survival in unresectable stage 2/3 NSCLC

3054

Background: Circulating stromal cells, ie Cancer Associated Macrophage-Like cells (CAMLs), are prevalent in the circulation of non-small cell lung carcinoma (NSCLC) patients (pts), appearing as giant phagocytic macrophages that represent an inflammatory pro-tumorigenic microenvironment. Previously it was shown that pts with engorged CAMLs of ≥50µm after treatment are prognostic for poor clinical outcomes. However, analyzing the dynamic changes in CAMLs over time or in response to treatment, ie chemoradiation (CRT) and immunotherapy (IMT) has not been evaluated. We monitored n = 182 unresectable NSCLC stage II/III pts treated with CRT alone (n = 91) or with concurrent IMT (n = 91) to evaluate changes in CAMLs before and after CRT induction at it relates to progression free survival (PFS) or overall survival (OS). Methods: We prospectively procured pts from 3 different regimes, treated with CRT alone (n = 91), treated concurrently with CRT & Atezolizumab (n = 40, clinical trial NCT02525757), or treated concurrently with Durvalumab (n = 51). We recruited 182 pts with pathologically confirmed stage II/III unresectable NSCLC. A total of 15 mL blood samples were drawn prior to start of therapy at baseline (BL) and ̃5 weeks (T1) after CRT induction. Blood filtration was done using CellSieve filters, then CAMLs were identified and measured to evaluate PFS & OS hazard ratios (HRs) by censored univariate and multivariate analyses at 2 years. Results: CAMLs were found in 89% of all samples tested. Increases in CAML size between BL & T1 were significantly correlated with worse clinical outcomes, with higher CAML increases correlated with increasingly worse outcomes, including CAML increases >10μm resulting in PFS HR=1.7 p = 0.027 & OS HR=1.9 p = 0.045, through increases >40μm resulting in PFS HR=2.1 p = 0.013 & OS HR=2.5 p = 0.020. Increases of CAMLs >35μm was optimal at stratifying pts PFS HR=2.2 p = 0.005 & OS HR=2.8 p = 0.005. Specifically, pts treated with only CRT and increasing CAMLs >35μmhad significantly worse PFS HR=2.7 p = 0.029 & OS HR=4.1 p = 0.013. In parallel, pts treated with CRT+IMT and increasing CAMLs >35μm had near significance for worse PFS (HR=2.1 p = 0.073) & OS (HR=2.3, p = 0.147), though follow up clinical data is ongoing. Conclusions: Our data suggest that in unresectable stage II/III NSCLC, tracking the increase of pro inflammatory immune cells (CAMLs) in circulation during therapy induction can identify pts less responsive to CRT or PD-L1/PD-1 IMTs.

Clinical Applications of Cancer-Associated Cells Present in the Blood of Cancer Patients

The ability to obtain tumor material from cells in the blood of cancer patients provides a significant benefit over the use of tumor tissue as a diagnostic to make treatment decisions. However, the traditionally defined circulating tumor cell (CTC) has been shown to be useful only in some cases. A recently identified type of circulating stromal cell, which appears to be more frequent than CTCs, was found engulfing tumor material at the tumor site and then entering the blood stream. These cells were defined as cancer-associated macrophage-like cells (CAMLs). Together, CTCs and CAMLs may be able to provide information for cancer detection and diagnosis, without the use of tissue. CTCs and CAMLs have many clinical applications, three of which are summarized in this review: for prognosis, as companion diagnostics, and for residual disease monitoring.

Abstract 589: CCR5 upregulation in two subtypes of tumor associated circulating cells predict worse prognosis in metastatic breast cancer

Background:

CCR5 is a motility chemokine receptor implicated in tumor progression, whose activation and endocytosis may identify highly aggressive breast cancer (BC) subtypes likely to spread via the circulatory system. We first studied the activation and endocytosis of CCR5 in response to its ligand CCL5 (RANTES) in the model BC cell line MDA-MB231. We then screened two types of circulating tumor-associated cells (TACs) with known negative clinical outcomes, 1) circulating tumor cells (CTCs) and 2) cancer-associated macrophage-like (CAMLs) cells, to evaluate CCR5 upregulation in relation to disease progression in metastatic breast cancer (mBC).

Methods:

MB231 cells were used to visualize CCR5 activation within the cell's surface and intracellular space using an anti-CCR5 antibody after stimulation with RANTES. MB231 cells were stained with LAMP-1A to verify co-localization of CCR5 and RANTES to endosomes. Anonymized peripheral blood samples from (n=54) mBC patients were obtained in accordance with local IRB regulations and with informed consent. TACs were isolated using a low-flow CellSieve Microfiltration system and stained for Cytokeratin, CD45, and CCR5. CCR5 expression signal and localization were evaluated on all TACs via fluorescence microscopy.

Results:

CCR5 in MB231 cells appeared as ~1μm clusters known as “CCR5 pools”, which can be found on the cell's surface, within the cytoplasm, and in the nuclear space. CCR5 pools were upregulated in the presence of RANTES, which appears to relate to endocytosis and nuclear translocation. Within the TACs of mBCs, we found similar patterns of CCR5 pooling with 70% of patients (n=38) having CCR5+ CAMLs and 41% (n=22) having CCR5+ CTCs. It was found that higher numbers of CCR5 pools (≥10pools/cell) were correlated to a 2-fold increase in both CTCs and CAMLs in circulation. In the analysis of outcome data, it was determined that patients having ≥10 CCR5 pools on their CAMLs was a highly significant predictor of worse progression free survival (PFS) and overall survival (OS) (PFS HR=4.8, CI 95% 1.9-11.6, p=0.0015) and (OS HR=3.6, CI 95% 1.3-10.0, p=0.0331). In CTCs ≥10 pools/cell was not a significant predictor for worse PFS and OS. However, ≥5 CCR5 pools/cell significantly predicted for worse PFS but not OS (PFS HR=2.9, CI 95% 1.2-7.4, p=0.0418 and OS HR=3.3, CI 95% 1.1-9.3, p= 0.0539).

Conclusion:

We observed the activation and endocytosis of CCR5 pools using RANTES in MD-MB231 cell lines, and then demonstrated that this upregulated motility pathway appears to be conserved in migratory cells in mBC patients. Further, this upregulation of CCR5 appears to correlate with worse clinical outcomes, which may provide an explanation for how tumor-associated cells move into circulation and acquire metastatic potential.

Citation Format: Ashvathi Raghavakaimal, Massimo Cristofanilli, Cha-Mei Tang, R. K. Alpaugh, Kirby P. Gardener, Saranya Chumsri, Daniel L. Adams. CCR5 upregulation in two subtypes of tumor associated circulating cells predict worse prognosis in metastatic breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 589.

Abstract 670: CXCR4 expression in tumor associated circulating cells of patients with pancreatic cancer is prognostic for progression and overall survival

Background:

CXCR4 is a chemotaxis receptor implicated in the progression of Pancreatic Cancer (PC) via the activation and invasion of tumor cells. To better elucidate its role in the PC metastasis, we examined the role of CXCR4 expression on a variety of tumor associated circulating cells (TACs) [i.e. circulating tumor cells (CTCs), epithelial to mesenchymal cells (EMTs), and cancer associated macrophage-like cells (CAMLs)] as it relates to patient outcomes. A PC cell line PANC-1 was used to model the activation and expression pathway of CXCR4 in cells. Then blood samples were procured from 30 PC patients prior to the start of therapeutic intent to evaluate CXCR4 expression in TACs. CAMLs, EMTs, and CTCs were found in 93%, 63%, and 30% of PC patients respectively, with high CXCR4 expression found to significantly relate with higher TAC populations in circulation. Further, in a 2-year univariate analysis it was found that high expression of CXCR4 in CAMLs or EMTs was significantly related to both progression free survival (PFS) and overall survival (OS). These data suggest that CXCR4 expression in circulating cells in PC is strongly related to the progression and metastatic spread of the disease.

Methods:

PANC-1 cells were used to examine the expression and upregulation of CXCR4 by staining with an anti-CXCR4 antibody after stimulation with Isoproterenol. A prospective pilot study was initiated using anonymized peripheral blood samples from (n=30) PC patients, obtained in accordance with local IRB regulations with informed consent. TACs were isolated from the blood using a low-flow CellSieve Microfiltration system and stained for cytokeratin, CXCR4, and CD45. Wilcoxon ranked sum test and univariate analysis were used to analyze the association of CXCR4 expression on all TACs and to evaluate 24-month PFS/OS.

Results:

Within the PANC-1 cell line, we observed a median expression of CXCR4 intensity of roughly 210 after activation and upregulation with Isoproterenol. Within TACs in the circulation, higher numbers of CAMLs (p=0.017), EMTs (p=0.001), and CTCs (p&lt;0.001) were all significantly related to cells with ≥210 CXCR4 expression. Further, higher expression of CXCR4 on CAMLs correlated with worse PFS (HR=4.0, 95%CI 1.5-10.5, p=0.012) and worse OS (HR=4.8, 95%CI 1.7-13.1, p=0.006), with higher CXCR4 expression in EMTs also correlated with worse PFS (HR=4.6, 95%CI 1.2-15.4, p=0.033) and worse OS (HR=5.4, 95%CI 1.5-19.2, p=0.021). Expression of CXCR4 in CTCs was not significant for PFS or OS.

Conclusion:

Expression of chemotaxis related receptor CXCR4 appears to have a strong relationship to higher numbers of TACs in circulation. This higher CXCR4 expression in CAMLs and EMTs also appears to correlate with rapid progression and death, indicating a relationship CXCR4 in the spread of PC and its potential use as a target for therapy.

Citation Format: Kirby P. Gardner, Susan Tsai, Mohammed Aldakkak, Stephen Gironda, Cha-Mei Tang, Daniel L. Adams. CXCR4 expression in tumor associated circulating cells of patients with pancreatic cancer is prognostic for progression and overall survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 670.

Abstract 357: Cancer associated macrophage like cells predict aggressive disease in local and metastatic prostate cancers

Background:

Prostate cancers (PC) are intrinsically complex, with few prognostic biomarkers that differentiate aggressive and indolent disease. Cancer associated macrophage like cells (CAMLs) have shown to be significant independent prognostic indicators for poor survival in tumors if engorged to ≥50μm. However, no group has examined CAMLs' in PC. In this prospective pilot study, we analyzed PSA & ≥50μm CAML presence in (n=51) Stage I-III & (n=41) metastatic PC (mPC) prior to the start of new treatments to examine CAMLs' on outcomes. We found that ≥50μm CAML presence significantly predicted worse patient survival in mPC. These preliminary results suggest that CAMLs may serve as a cheap, non-invasive prognostic biomarker that predicts for worse outcomes in both local & mPC prior to new therapies.

Methods:

We prospectively recruited (n=92) PC patients in this pilot study to examine CAML's prognostic significance in non-metastatic (stages I-III) and mPC. Of (n=92) total patients, 15% (n=14/92) were stage I, 32% (n=29/92) stage II, 9% (n=8/92) stage III, and 45% (n=41/92) Stage IV. Prior to the induction of new therapy or first line therapy for newly diagnosed patients, 7.5mL peripheral baseline (BL) blood was collected. Blood was filtered via CellSieveTM microfiltration, which excludes cells by size ≥7μm. In parallel, changes in PSA was monitored to compare prognostic significance against ≥50μm CAMLs. Wilcoxon univariate analysis was used to analyze ≥50μm CAMLs and PSA in progression free survival (PFS) and overall survival (OS).

Results:

CAML's were identified in 78.9% (n=71/90) of available BL samples, with two samples failing from clotting. Stage I-III patients had an average of ~3 CAMLs/7.5mL blood, whereas mPCs contained ~6 CAMLs/7.5mL. Average CAML size increased linearly with advancing stage of disease with stage I patients averaging 23μm, stage II 33μm, stage III 65μm, and stage IV 78μm. Of available BL samples, 41% (n=38/90) patients with ≥50μm CAMLs significantly predicted for worse PFS (HR=10.0, p&lt;0.001, 95%CI=0.07-0.31) and OS (HR=34.2, p&lt;0.001, 95%CI=0.03-0.21). Further, ≥50μm CAMLs significantly predicted for poorer survival in mPC with PFS (HR=9.4, p=0.028, 95%CI=0.18-0.84) and OS (HR=5.1, p=0.003, 95%CI=0.07-0.53), but only non-significantly trended in non-metastatic disease. Initial analysis of PSA found that high PSA at BL was a significant predictor for worse outcomes in patients, while changes in PSA was not a predictor.

Conclusions:

CAMLs have shown potential as a predictive non-invasive blood based biomarker across multiple solid malignancies, and here we compared this biomarker in PC. While preliminary, these data suggests that engorged CAML presence prior to the start of new treatment may be a statistically significant predictor of survival in both the local and metastatic setting, and a larger validation cohort should be established.

Citation Format: Daniel J. Gironda, Raymond Bergan, R K. Alpaugh, Daniel C. Danila, Tuan L. Chuang, Brenda Y. Hurtado, Thai Ho, Cha-Mei Tang, Daniel L. Adams. Cancer associated macrophage like cells predict aggressive disease in local and metastatic prostate cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 357.

Hyper engorged cancer associated macrophage-like cells in circulation predict for multi-organ metastatic disease in solid tumors

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Background: Patients with multiple organ metastases have poorer prognoses than those with a single organ metastasis, are frequently associated with drug resistance, and have higher tumor burden. Engorged (≥50um) Cancer Associated Macrophage-Like Cells (CAMLs) are a circulating stromal cell subtype detected in the blood of patients with solid tumors at high risk for recurrence or progression. While numerous studies have shown that ≥50um CAMLs predict poor clinical outcomes, meta-analysis of these studies have also suggested that hyper engorged CAMLs ≥100um (heCAMLs) may be associated with multifocal metastatic disease and even worse outcomes. In this prospective study, we evaluated the presence of heCAMLs in patients with metastatic disease and demonstrated a strong relationship with multi organ spread, which also correlated with shorter Progression Free Survival (PFS) and Overall Survival (OS). Methods: We prospectively recruited 151 patients with metastatic (m) mbreast (n = 58), mlung (n = 34), mprostate (n = 39), and mrenal (n = 20) cancers. Peripheral blood was collected prior to the induction of new treatment for metastatic cancer. Cells were isolated following standard CellSieve techniques, then imaged and measured in ZenBlue. Multi organ metastasis was defined as spread to ≥2 distant organ sites, or any spread to the brain. Single factor ANOVA was conducted to compare heCAML presence in multi organ metastatic patients versus patients with single organ site metastasis. Univariate and multivariate analysis was run to evaluate for PFS and OS against heCAMLs, and all known clinical parameters. Results: 150 viable samples (excluding 1 failed sample) were obtained. Multi organ metastases were present in 55% (n = 83/150) of patients. heCAMLs were found in 59% (n = 49/83) of the multi organ metastatic population, but only in 16% (n = 11/67) of the single site metastatic cohort (p < 0.001). heCAML presence appeared to differentiate multi organ vs single organ metastases in mbreast (85% vs. 52%, p = 0.006), mlung (71% vs. 26%, p = 0.025), mprostate (75% vs. 37%, p = 0.029), and mRCC (88% vs. 36%, p = 0.025). Further, in all n = 150 patients, heCAML presence predicted a significantly shorter median PFS of 4.5 versus 7.2 months, 24 month PFS (HR = 1.67, 95%CI = 1.13-2.45, p = 0.013), and significantly shorter median OS of 13.1 versus 20.4 months, 24 month OS (HR = 2.05, 95%CI = 1.24-3.39, p = 0.008). Conclusions: We examined a non-invasive prognostic blood based assay to determine its relationship to multi organ metastatic spread as well as its prognostic value in several solid cancers. These results showed patients with heCAMLs had higher rates of multi organ metastases, and appear to predict for shorter PFS and OS. Studies of larger cohorts are needed for prospective validation of these initial findings.

Sequential monitoring of PD-L1 on circulating stromal cells in blood predicts PFS in NSCLC patients undergoing immunotherapy after definitive chemoradiation

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Background: Cancer Associated Macrophage-Like cells (CAMLs) are circulating stromal cells in the blood of patients (pts) with solid tumors that are phagocytic macrophages that may represent the inflammatory state of the tumor microenvironment. Previously, we demonstrated CAMLs ≥50µm after chemo-radiation therapy (CRT) in NSCLC is associated with worse progression free survival (PFS) and overall survival (OS). We also showed that PDL1 expression in CAMLs is dynamic & can change with CRT, difficult to assess with repeat biopsies, but possible with liquid biopsy. For this study we evaluated whether CAML properties can predict response to CRT with/without immunotherapy (IMT) agents in unresectable NSCLC. Methods: A single blind multi-year prospective study was undertaken to test the relationship of PDL1 expression and ≥50µm CAML size to PFS/OS in NSCLC, pre and post CRT with (n = 96) and without (n = 72) anti-PDL1/PD1 IMT. This included atezolizumab (prospective single arm NCT02525757) n = 39, durvalumab n = 52 or pembrolizumab n = 5 both after 2018 FDA approval. We recruited 168 pts with pathologically confirmed unresectable NSCLC prior to CRT. Blood samples 15 mL were taken at baseline (BL), CRT completion (T1), and ̃1 month after CRT (T2) (with n = 96 or without n = 72 IMT). Blood was filtered by CellSieve filtration and CAMLs quantified for size ( < 49 µm or ≥50 µm) and PDL1 expression to evaluate PFS and OS hazard ratios (HRs) by censored univariate and multivariate analysis at 24 months. Results: CAMLs were found in 90% of all samples, average 5.8 CAMLs/15mL. At BL, ≥50µm CAMLs did not predict PFS in CRT/IMT pts (HR 1.6, p = 0.220) nor CRT alone (HR 1.3, p = 0.593). However, after completion of CRT (T1) ≥50µm CAMLs predicted PFS in CRT/IMT pts (HR 2.7, p = 0.003) and CRT alone (HR 2.5, p = 0.015). In primary tumor biopsies, PDL1 expression > 1% did not predict CRT/IMT response (PFS HR 1.8, p = 0.262 & OS HR 2.3, p = 0.158). At BL, high CAML PDL1 did not predict PFS in CRT/IMT pts (HR 1.4, p = 0.427) nor CRT alone (HR 1.1, p = 0.982). Further, at CRT completion (T1), high CAML PDL1 only trended for better PFS in CRT/IMT pts (HR 1.7, p = 0.137), but not CRT alone (HR 1.1, p = 0.972). At T2, however, pts with continuously high CAML PDL1 had significantly better PFS with IMT (HR 3.2, p = 0.002) vs CRT alone (HR 1.4, p = 0.616). While ≥50µm CAMLs at BL did not predict 24 month progression, ≥50 µm CAMLs after CRT (with or without 1 cycle of anti-PDL1 IMT) was 84% accurate at predicting progression. Further subtyping and analysis is ongoing to evaluate OS and PDL1 in the CAML populations. Conclusions: Our data suggests that in unresectable NSCLC, ≥50 µm CAMLs after completion of CRT is prognostic regardless of IMT use. PDL1 expression in CAMLs also appears to predict for response to consolidated IMT after CRT. Additional studies are needed to validate these findings.

Giant Circulating Cancer-Associated Macrophage-Like Cells Are Associated With Disease Recurrence and Survival in Non-Small-Cell Lung Cancer Treated With Chemoradiation and Atezolizumab

BACKGROUND

Cancer-associated macrophage-like cells (CAMLs) are a potential peripheral blood biomarker for disease progression. This study used data from a phase 2 clinical trial to evaluate prognostic utility of CAMLs for locally advanced non-small-cell lung cancer treated with definitive chemoradiotherapy (CRT) and atezolizumab (DETERRED; ClinicalTrials.gov NCT02525757).

PATIENTS AND METHODS

Sample collection occurred at baseline (T0), during CRT (T1), at end of CRT (T2), and at first follow-up (T3). CAMLs were captured and quantified by the CellSieve system using multiplex immunostaining. Giant CAMLs were defined as characteristic CAMLs ≥ 50 μm. Kaplan-Meier methodology estimated progression-free survival, distant failure-free survival, relapse-free survival, and overall survival at 30 months.

RESULTS

Thirty-nine patients were evaluated between December 2015 and March 2018. Median follow-up was 27 months. Most disease was stage III (85%) and comprised squamous-cell carcinoma (38%) or adenocarcinoma (59%). In total, 267 blood samples were analyzed. Giant CAMLs were identified in 57%, 60%, 64%, and 63% of patients at T0, T1, T2, and T3, respectively. Patients with giant CAMLs at T3, occurring at a median of 30 days after completion of CRT, had significantly worse distant failure-free survival (hazard ratio [HR] 4.9, P = .015), progression-free survival (HR 2.5, P = .025), recurrence-free survival (HR 2.4, P = .036), and overall survival (HR 3.5, P = .034) compared to patients with small or no CAMLs.

CONCLUSIONS

Presence of giant CAMLs after CRT completion was associated with development of metastatic disease and poorer survival despite the use of maintenance immunotherapy. Monitoring CAMLs may help risk-stratify patients for adaptive treatment strategies.

Circulating stromal cells in resectable pancreatic cancer correlates to pathological stage and predicts for poor clinical outcomes

Pancreatic cancer (PC) is notoriously difficult to diagnosis and properly stage resulting in incorrect primary treatment. Diagnostic and prognostic biomarkers are desperately needed to more accurately stage patients and select proper treatments. Recently, a newly discovered circulating stromal cell, i.e. cancer associated macrophage-like cell (CAML), was found to accurately identify solid cancers and predict for worse prognosis. In this pilot study, blood samples were procured from 63 PC patients prior to start of therapeutic intent. CAMLs were found in 95% of samples tested, with ≥12 CAMLs/7.5 mL and ≥50 µm CAMLs both predicting for advanced pathological stage and progression free survival. These data suggest that CAML assessment prior to treatment of PC predicts patients with under-staged disease and with more aggressive PC less likely to respond to standard of care treatment.

Abstract PS2-23: Prospective study of circulating cancer-associated macrophage-like cells (CAMLs) in obese patients with advanced breast cancer

Background

Cancer-associated macrophage-like cells (CAMLs) are rare circulating gigantic atypical cells exclusively found in the peripheral blood of patients with solid cancers. CAMLs potentially originate from tumor-associated macrophages in the tumor microenvironment and may have a prognostic role in breast cancer. Obesity-induced local hypoxia attracts macrophages to the tumor microenvironment and activates macrophages to induce chronic inflammation, which can lead to breast cancer progression. However, little is known about the relationship between CAMLs, obesity, and body fat distribution. Also, the role of the CAMLs on breast cancer development needs to be investigated. We hypothesized that the number and size of CAMLs are correlated with body mass index (BMI), and we investigated the relationship between CAMLs and body composition.

Materials and methods

We prospectively collected 10 ml of peripheral blood from 30 patients initially diagnosed with advanced breast cancer who underwent computed tomography. Blood samples were drawn in CellSave tubes to preserve peripheral blood mononuclear cells. We used the CellSieve microfiltering system to isolate and identify CAMLs. After enumerating cells, we analyzed immunofluorescent staining for DAPI, CD14, CD45, CXCR4, and cytokeratin. CAMLs were identified by cell surface markers (CD14+, CD45+, and cytokeratin+) and morphology (multinuclear and giant cells &gt;30 µm). BMI was measured at the time of diagnosis. The in-house 3D imaging analysis software Medical Executable for the Efficient and Robust Quantification of Adipose Tissue was used to calculate the total amount of abdominal visceral fat tissue (VAT) and subcutaneous fat tissue (SAT) between the upper diaphragm and pelvic end using multi-detector computed tomography data. The VAT:SAT ratio was also calculated. We quantified the expression of C-X-C chemokine receptor type 4 (CXCR4) in CAMLs to investigate the metastatic potential of the cells. Finally, we determined the relationship between the characteristics of CAMLs and BMI, body composition parameters, and CXCR4 using the Pearson correlation test.

Results

Of 30 collected samples, two had an inadequate amount of blood for evaluation. Among the remaining 28, we detected CAMLs in 24. The median BMI was 30.4 kg/m2, and half of the patients were categorized as obese by the World Health Organization BMI classification. BMI was correlated with the number (r=0.39, p=0.043), average size (r=0.42, p=0.039), and maximum size (r=0.50, p=0.013) of CAMLs. In body composition analysis, the maximum size of CAMLs was correlated with the total amount of VAT (r=0.51, p=0.012) and SAT (r=0.44, p=0.037) but not the VAT:SAT ratio. The number of CAMLs was correlated with maximum CXCR4 expression in CAMLs (r=0.58, p=0.004). CAMLs size and CXCR4 expression were inversely correlated.

Conclusion

The number and size of CAMLs are correlated with BMI, but CAMLs characteristics are not related to body composition. The number of CAMLs was associated with CXCR4, which indicated its metastatic potential. Further studies are needed to elucidate the biological role of CAMLs, especially whether the increased number and size of CAMLs in obesity reflect the tumor microenvironment.

Citation Format: Toshiaki Iwase, Aaroh Parikh, Onur Sahin, Akshara S Raghavendra, Maryanne E Sapon, Anjali James, Tushaar V Shrimanker, Sudpreeda Chainitikun, Kumiko Kida, Daniel L Adams, Cha-Mei Tang, Andrea YD Medrano, Ann H Klopp, Naoto T Ueno. Prospective study of circulating cancer-associated macrophage-like cells (CAMLs) in obese patients with advanced breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-23.

Cancer associated macrophage-like cells and prognosis of esophageal cancer after chemoradiation therapy

BACKGROUND

Cancer Associated Macrophage-Like cells (CAMLs) are polynucleated circulating stromal cells found in the bloodstream of numerous solid-tumor malignancies. Variations within CAML size have been associated with poorer progression free survival (PFS) and overall survival (OS) in a variety of cancers; however, no study has evaluated their clinical significance in esophageal cancer (EC).

METHODS

To examine this significance, we ran a 2 year prospective pilot study consisting of newly diagnosed stage I-III EC patients (n = 32) receiving chemoradiotherapy (CRT). CAML sizes were sequentially monitored prior to CRT (BL), ~ 2 weeks into treatment (T1), and at the first available sample after the completion of CRT (T2).

RESULTS

We found CAMLs in 88% (n = 28/32) of all patient samples throughout the trial, with a sensitivity of 76% (n = 22/29) in pre-treatment screening samples. Improved 2 year PFS and OS was found in patients with CAMLs < 50 μm by the completion of CRT over patients with CAMLs ≥ 50 μm; PFS (HR = 12.0, 95% CI = 2.7-54.1, p = 0.004) and OS (HR = 9.0, 95%CI = 1.9-43.5, p = 0.019).

CONCLUSIONS

Tracking CAML sizes throughout CRT as a minimally invasive biomarker may serve as a prognostic tool in mapping EC progression, and further studies are warranted to determine if presence of these cells prior to treatment suggest diagnostic value for at-risk populations.

Abstract CT233: Phase Ib/II study of leronlimab (PRO 140) combined with carboplatin in CCR5+ mTNBC patients

Introduction: Triple Negative Breast Cancer (TNBC) represents the most deadly form of invasive disease. It is associated with clinical and pathological features of highly proliferative and rapidly spreading cancer demonstrating higher incidence in younger women, particularly of African-American ethnicity and accounting for a disproportionately high percentage of early development of metastatic disease and breast-cancer-related death. While chemotherapy remains the main treatment option for both primary and metastatic TNBC (mTNBC) there is no optimized therapy for its management due to tumor heterogeneity, leaving the condition with an unmet medical need. Recent preclinical research demonstrated an important role for chemokine receptor type 5 (CCR5) in modulating cell migration and immune microenvironment suggesting a potential new therapeutic target in mTNBC [Jiao X et al, Can Res 2018;78:1657-71]. Leronlimab (PRO 140) is a humanized IgG4,к monoclonal antibody (mAb) to the C-C chemokine receptor type 5 (CCR5). Leronlimab has been administered and generally well tolerated in more than 750 healthy and HIV-1 infected individuals in Phase I/II/III studies. An ongoing Phase Ib/II study is being conducted to assess the safety and clinical outcomes of leronlimab combined with carboplatin in patients with untreated CCR5+ metastatic Triple Negative Breast Cancer (mTNBC). Methods: Eligible patients are required to have confirmed HER2 negative, ER &lt;1%, PR&lt;1% and demonstrate CCR5+ by immunohistochemistry assay (IHC) (&gt;10% of primary or metastatic cancer cells shows membranous staining and/or high predominance of CCR5+ tumor-infiltrating leukocytes (see representative IHC staining images below) Phase Ib of the CD07_TNBC study is a multicenter, single arm, dose escalation phase with 3 dose levels of leronlimab administered in combination with a fixed dose of carboplatin at AUC 5. The starting dose is 350 mg with escalation to 525 mg and 700 mg in the absence of dose-limiting toxicities. Leronlimab is administered as subcutaneous injection in the abdomen weekly and can be self-administered by subjects at home after proper training by a healthcare professional. Carboplatin is administered at AUC 5 every 3 weeks. The maximum tolerated dose (MTD) of leronlimab determined during the Phase Ib portion will be administered to 30 patients during the Phase II portion of the study. Correlative Data: Blood samples are collected at Day 1 of each treatment cycle (every 21 days) to assess changes in circulating tumor cells (CTCs) and cancer associated macrophage-like cells (CAMLs) after treatment and to perform correlative analysis with CCR5 expression. Conclusions: Leronlimab (PRO 140), a CCR5 antagonist mAb, in combination with carboplatin is currently enrolling newly diagnosed mTNBC. The preliminary analysis shows safety and tolerability of the combination and continue to enroll patients with initial promising clinical activity, potentially suggesting the future availability of a new effective agent in the management of this serious condition.

Citation Format: Massimo Cristofanilli, Milana Dolezal, Jay Lalezari, Hallgeir Rui, Bruce Patterson, Cha-Mei Tang, Daniel Adams, Qiang Zhang, Kazem Kazempour, Nader Pourhassan, Natalie Rabb, Kush Dhody. Phase Ib/II study of leronlimab (PRO 140) combined with carboplatin in CCR5+ mTNBC patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT233.

Abstract 3297: Expression of pd-l1 on circulating stromal cells predicts immunotherapy response in unresectable non-small cell lung carcinoma after definitive chemoradiotherapy

Background: Circulating stromal cells (CStCs) have been found to be common in the peripheral blood of cancer patients and hypothesized to be a blood based biomarker for monitoring cancer treatment. It has previously been described that the dynamic changes of PD-L1 expression during chemoradiotherapy (CRT) could be tracked using circulating stromal cells. However, how these changes relate to PD-L1/PD-1 immunotherapy (IMT) response is unstudied. We prospectively monitored PD-L1 expression in 2 cell types found in circulation (Circulating Tumor Cells [CTCs] and Cancer Associated Macrophage-like Cells [CAMLs]) in locally advanced non-small cell lung cancer (NSCLC) patients (pts) treated with Atezolizumab (Atezo) after definitive CRT (n=39) or in pts with CRT alone (n=40).

Methods: A 2 year single blind prospective study was undertaken in pts with locally advanced NSCLC in 40 patients treated with CRT alone, or from a phase II DETERRED trial (NCT02525757) where Atezo was added for 1 year after completing CRT (n=10), or concurrently and after CRT (n=30). Samples from 39 of 40 pts from the DETERRED study were available for analysis. Baseline blood samples (7.5 ml) were drawn prior to start of CRT (T0), and a second sample was drawn ~1 month after completing CRT (T1), but prior to induction of Atezo. Blood was processed by CellSieve™ microfilters; stained for cytokeratin/PDL1/CD45 to identify CTCs and CAMLs. PD-L1 intensity was measured and grouped by 4 scores: 0-negative, 1-low, 2-medium, & 3-high. PD-L1 levels from circulating cells were used to evaluate PFS and OS. Significance was assessed by log-rank testing.

Results: At least one CTC and/or CAML was found in 91% of available T0 samples and 96% of available T1 samples. In the 40 patients that received CRT alone, 35 pts had measurable cells at T0 and PD-L1 expression in CStCs was low (0-1) in 20 pts and high (2-3) in 15 pts. Further, at T1 PD-L1 expression in CStCs was low in 12 pts and high in 28 pts, with no relationship to PFS (T0 HR=1.1, 95%CI 0.5-2.8, p=0.96 and T1 HR=0.8, 95%CI 0.3-2.0, p=0.82) or OS (T0 HR=0.8, 95%CI 0.2-2.8, p=0.99 and T1 HR=1.1, 95%CI 0.3-3.5, p=0.84). In the patient arm that received Atezo at T0, PD-L1 expression in CStCs was low in 21 pts and high in 17 pts, with no relationship to PFS (HR=0.5, 95%CI 0.2-1.7, p=0.18) or OS (HR=1.6, 95%CI 0.4-6.0, p=0.75). However at T1, pts with high PD-L1 had significantly improved PFS response to Atezo (HR 5.4, 95%CI 1.7-17.0, p=0.009), and improved OS (HR 21.5, 95%CI 4.5-91.9, p&lt;0.001).

Conclusions: PD-L1 expression in tissue is often not used in IMT treatment decisions due to limited correlation with clinical responses. However, it has been suggested that sequential monitoring of PD-L1 expression in circulating stromal cells in blood may predict for patients who will respond to IMT. These data suggests that CRT altered PD-L1 expression, and monitoring dynamic changes of PD-L1 in CStCs may predict immunotherapy effectiveness in NSCLC after CRT.

Citation Format: Daniel L. Adams, Jianzhong He, Yawei Qiao, Kirby P. Gardner, John V. Haymach, Anne S. Tsao, Ashvathi Raghavakaimal, Cha-Mei Tang, Alexander Augustyn, Steven H. Lin. Expression of pd-l1 on circulating stromal cells predicts immunotherapy response in unresectable non-small cell lung carcinoma after definitive chemoradiotherapy [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3297.

Abstract 6478: Circulating stromal cells in resectable pancreatic cancer is associated with high pathological stage and poor clinical outcomes

Background: Pancreatic cancer (PC) is a difficult malignancy to diagnosis and properly stage, with extremely poor outcomes even for patients (pts) with resectable disease. Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common to the blood of cancer pts, whose presence and size (≥50µm) is a prognostic indicator of poor progression free survival (PFS) and overall survival (OS). However, the clinical value of CAMLs in PC has not been evaluated. We recruited treatment naïve PC pts referred for surgical resection before therapy induction to study CAML association to PFS/OS. We investigate whether a simple blood test can better identify pts with metastatic disease and act as a predictor for PFS and OS.

Methods: 68 whole peripheral blood samples were drawn from untreated newly diagnosed PC pts referred for surgical resection prior to induction of therapy. Pts were recruited for a 2 year single blind prospective pilot study testing &gt;5 CAMLs, CAML size (≥50µm), CA19-9, & CEA to clinical stage (CS), pathological stage (PS), and resectability. Pts were referred based on CS with resectable (R) (n=23), borderline resectable (BR) (n=27), or locally advanced (LA)/metastatic (M) (n=16); Stage I (n=50), Stage II (n=12), Stage III (n=0), Stage IV (n=3), and unknown stage (n=2). Blood samples (7.5mL) were taken prior to any neoadjuvant therapy. Blood was filtered by CellSieveTM filtration and CAMLs quantified. Analysis of CAMLs, protein markers, and resectability were used to evaluate PFS and OS significance by log-rank testing.

Results: CAMLs were found in 92% (n=61/66) of pt samples and averaged 7.5 CAMLs/7.5 mL blood. In pts that received surgery, 22 pts were upstaged with PS; stage I (n=20), Stage II (n=16), Stage III (n=5), Stage IV (n=18), & 7 pts withdrawing prior to surgery. All early stage pts with ≥12 CAMLs (n=6) were upstaged to metastatic disease after surgical resection. CEA and CA19-9 serum were not significant for PFS (CEA HR 0.9, p=0.639 and CA19-9 HR 0.6, p=0.288). Further, R vs BR was not significant for PFS (HR 0.4 p=0.10) nor was BR vs LA (PFS HR=0.2 p=0.075), though in both comparisons resectability did trend non-significantly toward better PFS. &gt;5 CAMLs was not a significant indicator of PFS or OS (PFS HR 0.6 p=0.175 and OS HR 1.0 p=0.902). However, ≥50µm CAMLs was a highly significant indicator of both PFS and OS (PFS HR 4.0 CI95% 2.0-7.8, p&gt;0.001 and OS HR 2.3 CI95% 1.1-4.7, p=0.035).

Conclusions: In PC, accurate staging/resectability is difficult, with 60% of pts being upstaged post-surgery and ~80% recurring in 2 years. There is a need for a better method to stratify surgical candidates that won't benefit from surgical resection. These data suggest that high CAML numbers at diagnosis identifies pts with metastatic disease which are less likely to benefit from surgical resection, and enlarged CAML size correlates to poorer PFS and OS.

Citation Format: Kirby P. Gardner, Daniel L. Adams, Mohammed Aldakkak, Cha-Mei Tang, Susan Tsai. Circulating stromal cells in resectable pancreatic cancer is associated with high pathological stage and poor clinical outcomes [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6478.

Circulating stromal cells as a potential blood-based biomarker for screening invasive solid tumors

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Background: Peripheral blood allows for a simple non-invasive method for isolating various cancer associated circulating stromal cells (CStCs) which may predict for cancer presence. Cancer Associated Macrophage-Like cells (CAMLs), a specific CStC, are phagocytic myeloid cells that derive from an immunological response to cancer and emanate from primary tumors. Using a filtration platform we screened the peripheral blood of untreated newly diagnosed cancer patients (n = 308) for CAMLs. In parallel, we screened patients with newly diagnosed non-malignant diseases, i.e. lupus, benign cysts, etc. (n = 39), and healthy control samples (n = 76). We found that CAMLs are highly prevalent (87%) in the blood of cancer patients, but uncommon in non-malignant conditions (20%) & absent in healthy individuals (0%). Methods: Anonymized peripheral blood were taken from 308 cancer patients after confirmation of invasive malignancy [stage I (n = 76), stage II (n = 73), stage III (n = 72), stage IV (n = 65) and unstaged non-metastatic (n = 22)] with pathologically confirmed lung (n = 65), pancreas (n = 53), breast (n = 52), prostate (n = 40), esophageal (n = 30), renal cell (n = 18), hepatocellular (n = 15), neuroblastoma (n = 10), melanoma (n = 8), and other (n = 17). Further, anonymized blood was taken from patients with untreated non-malignant conditions including benign breast masses (n = 19), lupus (n = 11), liver cirrhosis (n = 5), benign prostatic hyperplasia (BPH) (n = 3), and viral infection (n = 1); or from healthy control volunteers (n = 76). CAMLs were isolated from whole peripheral blood by the CellSieve™ microfiltration technique and defined as enlarged, multinuclear cells with cytokeratin and/or CD45/CD14 positive. Results: CAMLs were found in 87% of all cancer patients regardless of stage, ~5.4 CAMLs/7.5mL blood. Specifically, CAMLs were found in 80% of Stage I, 90% Stage II, 89% Stage III, and 97% Stage IV patients. No CAMLs were found in any healthy controls, but were found in 26% of benign breast masses, 18% of lupus, 0% of BPH and 0% of cirrhosis. In total, CAML sensitivity in cancer vs healthy was 87% (CI95% 82-90%), specificity = 100% (CI95% 95-100%), PPV = 100% (CI95% 100%), NPV = 67% (CI95% 58-71%). CAML sensitivity in cancer vs benign was 87% (CI95% 82-90%), specificity = 80% (CI95% 64-91%), PPV = 97% (CI95% 95-98%), NPV = 43% (CI95% 35-51%). Conclusions: CAMLs, a Circulating Stromal Cell subtype, is a sensitive blood based biomarker found in all stages of cancer that is rare in non-malignant conditions and absent in healthy individuals.

Sequential monitoring of circulating stromal cells from blood is predictive of progression in NSCLC patients undergoing anti-PD-L1 therapy after definitive chemoradiation therapy

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Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common in the peripheral blood of patients with solid tumors. In non-small cell lung carcinoma (NSCLC), patients with CAMLs ≥50µm after completion of chemoradiation therapy (CRT) have been shown to have worse progression free survival (PFS). However, with the recent addition of anti-PD-L1 therapies in conjunction with CRT as standard of care, it has never yet to be evaluated whether CAMLs remain predictive for monitoring progression in NSCLC patients post anti-PD-L1 therapy. Methods: A 2 year single blind prospective study was undertaken to test the relationship of ≥50µm CAMLs to PFS based on imaging in lung patients before and after induction of CRT and PD-L1. We recruited 104 patients with pathologically confirmed unresectable NSCLC Stage II (n = 14), Stage III (n = 83), Stage IV (n = 3), and locally recurrent disease (n = 4). Baseline (BL) blood samples were taken prior to start of therapy. A second time point blood sample (T1) was taken at the end of radiotherapy (~40 days). A third time blood sample (T2) was taken after induction of anti-PD-L1 therapy (e.g. Imfinizi, Keytruda, etc.). Blood was filtered by CellSieve filtration and CAMLs were quantified. Analysis by CAML size of < 49 µm or ≥50 µm was used to evaluate PFS hazard ratios (HRs) by censored univariate & multivariate analysis. Results: CAMLs were found in 87% of samples averaging 2.9 CAMLs/7.5mL sample. At BL, CAMLs ≥50 µm had similar PFS to patients with < 50 µm CAMLs (HR = 1.1 95%CI 0.6-1.95 p = 0.8661). However, after CRT (T1), patients with CAML size ≥50 µm had worse PFS (HR = 3.2, 95%CI 1.8-5.8 p = 0.0002). After induction of anti-PD-L1 therapy (T2), patients with ≥50 µm CAMLs also had worse PFS (HR = 2.8 95%CI 1.5-5.4 p = 0.0037). CAML size at BL was not accurate at predicting progression within 24 months; however ≥50 µm CAMLs after CRT or after 1 cycle of anti-PDL1 therapy was 71% accurate at predicting progression of disease. Conclusions: Our data suggests that in NSCLC, ≥50 µm CAMLs after completion of CRT or appearing after induction of anti-PD-L1 therapy appears to predict progressive disease. If validated, additional studies are needed to determine if CAMLs can serve as a significantly prognostic blood based marker for predicting survival in NSCLC patients early in the treatment regime.

Abstract P5-06-27: Circulating cancer associated macrophage-like cells (CAMLs) are early predictors of response to new line therapies in metastatic breast cancer

Background: Tumor-associated macrophages have been shown to play a critical role in metastasis, angiogenesis, and immune escape. Cancer associated macrophage-like cells (CAMLs) are circulating stromal cell with macrophage expression subtypes, detected in the peripheral blood of patients with solid tumors. We have previously shown that enlargement of CAML cells is an independent predictor of poorer overall survival and an indication of progression in patients with metastatic breast cancer (MBC). However changes in CAML sizes after induction of therapy has not been investigated. Here we evaluated the association between early changes in numbers and sizes of CAMLs as it relates to clinical response after induction of new therapy. Method: Peripheral blood samples from 29 patients with metastatic breast cancer who failed at least 2 prior lines of therapies were prospectively collected. Baseline (BL) blood samples were taken prior to initiation of a new therapy and the second samples (T1) were taken approximately 30 days after initiation of a new systemic therapy. Blood samples were filtered using CellSieveTM filtration. The quantity and size of CAMLs were measured then compared between the BL and T1 time points. Univariate analysis was used to determine the association of changes in CAML numbers and changes in CAML size, with objective response at the first follow up CT scan with progression free survival (PFS). Results: CAMLs were detected in 97% of BL samples (averaging 20.9 CAMLs/7.5ml blood) and 93% of T1 samples (averaging 18.5 CAMLs/7.5mL blood). At the time of the first follow up CT scan, 17 of 29 patients (58.6%) had progressive disease based on the RECIST criteria. Among those, 14 of 17 patients (82%) had an increase in CAML size (~85% overall enlargement) and 3/17 (18%) had a decrease CAML size (~60% overall shrinkage) in T1 samples compared to baseline. In contrast, 10 of 12 patients (83%) with clinical benefit, including stable disease and partial or complete response, had a 92% reduction in their CAML’s size and 2 of 12 patients (17%) had 61% enlargement in their CAML’s size after treatment. Overall, CAML size change after therapy induction was 83% accurate in predicting clinical benefit based on subsequent scans. Furthermore, patients with enlarging CAML size at T1 had significantly shorter PFS of 4 months compared to 10 months in patients with decreasing CAML size (HR 3.7; 95%CI1.5-10.1; p 0.020). Conclusion: CAMLs can be commonly found in most treatment-refractory metastatic breast cancer patients and their morphological size is clinically correlated to poorer survival. Our data suggests that monitoring the size changes of a patient’s CAMLs after 30 days of new treatment initiation may predict clinical benefit earlier than conventional scans and act as real time monitoring of MBCs response to new therapies. Additional studies are currently ongoing to validate these results.

Citation Format: Saranya Chumsri, Markus D. Lacher, William V. Williams, R. K. Alpaugh, Stuart S. Martin, Rena Lapidus, Cha-Mei Tang, Massimo Cristofanilli, Daniel L Adams. Circulating cancer associated macrophage-like cells (CAMLs) are early predictors of response to new line therapies in metastatic breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-27.

Effect of Cobalt Precursors on Cobalt-Hydroxyapatite Used in Bone Regeneration and MRI

In clinical dentistry practice, supplemental bone surgery or jawbone defect after tooth extraction must be assisted by a bone-filling material. Cobalt-substituted hydroxyapatite (COHA) effectively promotes bone cell growth, reduces the inflammatory response, and is an antibacterial agent. COHA can therefore be used as an alveolar bone-filling material or guided bone regeneration membrane. Meanwhile, COHA can be used in magnetic resonance imaging (MRI) with negative contrast agents and targeting materials without causing metal interference with the image. Hence, COHA has received increasing amounts of attention in recent years. However, the influence of different cobalt precursors on the synthesized COHA is still unknown. Therefore, COHA synthesized from 3 cobalt precursors (cobalt chloride, cobalt nitrate, and cobalt sulfate) was compared in this study. The results show that COHA synthesized by the precursor with the smallest anion radius, cobalt chloride, has a larger particle size (239 nm) and a higher cobalt ion substitution rate (15.6%). When the cobalt ion substitution rate increases, the MRI has a stronger contrast. Bioactivity data indicate that COHAC is more susceptible to degradation and therefore releases more cobalt ions to contribute to the differentiation of bone cells. Based on these studies, COHAC prepared with the cobalt chloride precursor has a higher cobalt ion substitution rate, faster degradation rate, better image contrast, and better bioactivity. It is therefore the preferred choice of bone-filling material for alveolar bone regeneration.

Abstract 2915: A circulating stromal cell subpopulation that accurately predicts resistance and progression in treatment naïve lung cancer patients receiving definitive radiotherapy

Background: Cancer Associated Macrophage-Like cells (CAMLs) are recently described circulating stromal cells common in the peripheral blood of cancer patients hypothesized to be a mechanism in cancer pathogenesis. We previously described that treatment naive patients with circulating CAMLs ≥50µm is a significant independent prognostic indicator of shorter progression free survival (PFS) in a variety of cancers. However, the clinical value of CAMLs in specific diseased cohorts for predicting response to treatment has not been evaluated. We present the results of a prospective study on treatment naive lung cancer patients before induction and directly after completion of definitive radiotherapy to determine if CAMLs are predictive of treatment response and cancer progression.

Methods: A 2 year single blind prospective study was undertaken, testing the relationship of enlarged CAMLs (≥50µm) to PFS of lung cancer patients before & after induction of definitive radiation therapy. To achieve a 2-tailed 95% power (α=0.05) we recruited a training set of 55 patients, all with pathologically confirmed lung cancer: Stage I (n=13), Stage II (n=7), Stage IIIa (n=10), Stage IIIb (n=18) & Stage IV (n=7). Baseline (BL) blood samples were taken prior to start of therapy. If possible, a second blood sample (T1) was taken after completion of radiotherapy (~60 days), n=46 patients. Blood was filtered by CellSieveTM filtration and CAMLs quantified. Analysis by CAML size of &lt;50 µm or ≥50 µm was used to evaluate PFS hazard ratios (HRs) by censored univariate & multivariate analyses.

Results: CAMLs were found in 93% of BL samples averaging 3.2 CAMLs/7.5mL. Patients with at least one CAML ≥50 µm had reduced PFS (HR=2.9, 95%CI 1.4-6.0, p=0.010). 46 patients agreed to a follow up blood draw. 13 of the 46 patients had an increase of CAML size to ≥50 µm, but 3 patients had a decrease to &lt;50 µm, resulting in an increase of PFS (HR=7.7, 95%CI 2.6-12.5, p&lt;0.001). Combined, 90% of patients with a ≥50 µm CAML at BL progressed within 2 years vs 46% of patients with &lt;50 µm CAMLs. Enlarged CAMLs at T1 was more predictive of progression, with 92% of patients with a ≥50 µm CAML progressing vs 21% of patients with &lt;50 µm CAMLs. Notably, 100% of patients that had a ≥50 µm CAML at both BL and T1 progressed. By comparison, only 11% of patients with &lt;50 µm CAMLs at both BL and T1 progressed. In a multivariate analysis, CAML size was the most significant indicator of PFS and OS, independent of all other clinical variables, including stage.

Conclusions: Our data suggests that for lung cancer patients undergoing definitive radiation therapy, the presence of enlarged CAMLs appears to predict patients that are resistant to treatment. Furthermore, these circulating stromal cells appear useful for sequential monitoring of patients that may prognosticate who are likely to progress after treatment.

Citation Format: Daniel L. Adams, Jianzhong He, Yawei Qiao, Hui Gao, James Reuben, Ignacio I. Wistuba, Cha-Mei Tang, Steven H. Lin. A circulating stromal cell subpopulation that accurately predicts resistance and progression in treatment naïve lung cancer patients receiving definitive radiotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2915.

Real-time monitoring of circulating stromal cells in the blood to predict responsiveness of new-line therapies in metastatic breast cancer

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Background: Cancer associated macrophage like cells (CAMLs), a circulating stromal cell subtype, has been shown as an independent prognostic indicator of survival in late stage metastatic breast cancer when cells enlarge to ≥50µm. However, no study has evaluated the clinical relationship between changes in CAML size and their ability to predict treatment response. While CAMLs are prognostic for progression, we hypothesized that monitoring changes in CAMLs after initiation of therapy may be predictive for responsiveness of new treatment regimens. Methods: A prospective 12 months blind multi-institutional pilot study was undertaken to evaluate CAMLs before, and after, induction of a new line of investigational therapy based on CT scans. Patients with progressive metastatic breast cancer (n = 29) who had failed at least 2 prior therapies were recruited. A baseline (BL) blood sample was taken prior to induction of a new therapy and a 2nd sample (T1) taken after initiation (~30 days). Blood was filtered by CellSieve filtration.The quantities and sizes of CAMLs were analyzed based on PFS hazard ratios (HRs) by censored univariate analysis. Results: CAMLs were found in 97% of BL samples and 93% of T1 samples. At first CT scan, after the assigned dose of investigational treatment, 17 of 29 patients had clinical progression with 14/17 (82%) patients having an increased CAML size and 3/17 (18%) having a decreased CAML size. The remaining 12 of 29 patients saw clinically stable, or regression, of disease with 10/12 (83%) having decreased CAML size and 2/12 (17%) having increased CAML size. Overall CAML size change after therapy induction was 83% accurate at predicting response or progression based on CT scans. Further, patients with increasing CAML size at T1 had a 4 month mPFS vs 10 month mPFS for decreasing CAMLs, with a lower 12 month PFS HR = 3.7 (95%CI = 1.5-10.1, p = 0.020). Conclusions: Our data suggests that in metastatic breast cancer, monitoring CAMLs changes over the first 30 days of treatment accurately predicts responsiveness of disease to new treatments. Further, we suggests using blood sampling may increase the clinical value of blood based diagnostics by rapidly predicting the benefit of subsequent therapies.

Training and validation study for sequential monitoring of CAMLs in circulation to predict ongoing progression in lung cancer patients undergoing definitive radiotherapy

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Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell common in the peripheral blood of cancer patients that are prognostic for progressive disease. Further, it has been shown that changes in CAML size (i.e. enlargement above 50µm) can predict progression free survival (PFS) in thoracic cancers (e.g. lung). We enrolled 104 unresectable non-small cell lung cancer (NSCLC) patients, with an initial training set review of 54 patients, to determine if change in CAML size after radiation therapy was predictive PFS. Methods: A 2 year single blind prospective study was undertaken to test the relationship of ≥50µm CAMLs to PFS based on imaging in lung patients before and after induction of chemo radiation, or radiation therapy. To achieve a 2-tailed 90% power (α = 0.05) we recruited a training set of 54 patients and validation set of 50 patients all with pathologically confirmed unresectable NSCLC: Stage I (n = 14), Stage II (n = 16), Stage III (n = 61) & Stage IV (n = 13). Baseline (BL) blood samples were taken prior to start of therapy & a 2nd blood sample (T1) was taken after completion of radiotherapy (~30 days). Blood was filtered by CellSieve filtration and CAMLs quantified. Analysis by CAML size of < 49 µm or ≥50 µm was used to evaluate PFS hazard ratios (HRs) by censored univariate & multivariate analysis. Results: CAMLs were found in 95% of samples averaging 2.7 CAMLs/7.5mL sample at BL, with CAMLs ≥50 µm having reduced PFS (HR = 2.2, 95%CI1.3-3.8, p = 0.003). At T1, 18 patients had increased CAML size ≥50 µm with PFS (HR = 4.6, 95%CI2.5-8.3, p < 0.001). In total, ≥50 µm CAMLs at BL was 76% accurate at predicting progression within 24 months while ≥50 µm CAMLs at T1 was 83% accurate at predicting progression. Conclusions: In unresectable NSCLC patients, enlargement of CAMLs during treatment is an indicator active progression. We identify that a single ≥50 µm CAML after induction of radiotherapy, in our training set and confirmed in our validation set, is an indicator of poor prognosis. We suggest that changes in CAML size during therapy may indicate the efficacy of therapy and could potentially help shape subsequent therapeutic decisions.

Abstract A012: SV-BR-1-GM, a whole-cell targeted immunotherapy for advanced breast cancer: Pharmacodynamic markers of response

Background: SV-BR-1-GM is a GM-CSF-engineered breast cancer cell line employed – after irradiation – as a targeted immunotherapy for advanced breast cancer. Tumor regressions at metastatic sites have been observed, most notably in patients with HLA allele matches to the cell line. We are assessing SV-BR-1-GM in the phase IIa portion of a phase I/IIa clinical trial in metastatic and locally recurrent breast cancer (ClinicalTrials.gov identifier NCT03066947). Additionally, we are co-developing a companion diagnostic (BriaDX™) to identify patients likely to respond to SV-BR-1-GM. Currently, BriaDX™ consists of HLA typing; however, we have begun assessing biomarkers in sera, lymphocyte characteristics, circulating tumor cells (CTCs), and cancer-associated macrophage-like cells (CAMLs) from patients collected at baseline and after inoculation of SV-BR-1-GM to layer in additional components to improve accuracy, with the number/subtyping of CTCs and CAMLs being prognostic indicators. Methods: Subjects are pretreated with low-dose cyclophosphamide to reduce immune suppression. SV-BR-1-GM is inoculated intradermally with follow-up local injections of IFNα2. Cycles are every 2 weeks x 3, then monthly. HLA typing was conducted via LabType R-SSO Kits (One Lambda). Cytokines were measured via single- or multiplex assays. Anti-SV-BR-1 antibodies were determined by incubation of SV-BR-1 cells with diluted patient sera followed by staining with a fluorescently-labeled anti-IgG antibody and detection by flow cytometry. CTCs and CAMLs were evaluated by CellSieve™ at Creatv MicroTech. Results: To date, 16 clinical trial subjects have been inoculated with the SV-BR-1-GM regimen as rescue immunotherapy. All were treatment refractory and had received a median of 4.5 prior chemo/biologic therapy regimens (range 1-13). Two of the 16 patients remained on study for ≥3 months (5 cycles) with 4 patients currently on study not having reached the 3-month evaluation time point. Objective regression of tumor was seen in 2 subjects. One subject had virtually complete regression of 20 of 20 lung metastases noted at 3 and 6 months (but with progressive bone and liver metastases). Another subject had improvement of chest wall metastases and quality of life but expired due to nontreatment-related causes. Response appeared to correlate with HLA allele-matching to SV-BR-1-GM. Anti-SV-BR-1 antibody titers increased in several patients. Among the cytokines assessed, interleukin (IL)-8 levels increased in HLA-DRB3 allele-matched subjects after SV-BR-1-GM inoculation. Of 15 patients evaluated, CTCs were present in 6 patients at baseline while CAMLs were present in all 15. Five of 5 patients evaluated for PD-L1 expression had mostly low-to-medium expression of PD-L1 on their CTCs/CAMLs. In the patient who had regression of lung metastases but progression of liver metastases, PD-L1 expression and maximum CAML size increased, but the number of CAMLs decreased during treatment. CAML number also decreased in a patient who reached the 3-month evaluation visit without progression and in a patient with inflammatory breast cancer who dropped out due to worsening inflammation. Conclusions: In addition to the patients’ HLA types, several pharmacodynamic parameters correlated with tumor regression and/or HLA matching status. CTCs or CAMLs are frequently detectable in this population, and PD-L1 expression appears common on these cells. Both CAML number and size appear to correlate with response, though larger studies are needed. Future steps include evaluation of SV-BR-1-GM with checkpoint inhibitors.

Citation Format: Markus D. Lacher, Sanne Graeve, Vivekananda (Vivek) Sunkari, Daniel L. Adams, Cha-Mei Tang, Pete Amstutz, Charles L. Wiseman, George E. Peoples, William V. Williams. SV-BR-1-GM, a whole-cell targeted immunotherapy for advanced breast cancer: Pharmacodynamic markers of response [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A012.

Abstract 1560: Real-time monitoring of solid tumor progression by circulating stromal cells from early- to late-stage disease

Background: Blood-based biomarkers (PSA, CEA, CA125) are used to track real-time progression of disease in parallel with imaging. However, while numerous blood biomarkers exist, they are specific to cancer type (i.e., PSA to prostate and CEA to colon) and may not appear in all diseased individuals. Recently, cancer-associated macrophage-like cells (CAMLs), a circulating stromal cell subtype, were identified in various solid cancer types, which were observed increasing in size and in hyperploidy during progressive disease. To assess whether CAML enlargement is a biomarker of progression/response, we tracked CAML growth/shrinkage in a pilot study of patients (n=34). Blood was drawn from patients with lung, prostate, or breast cancers over a 3-month period, baseline through 2 treatment cycles, followed by continued monitoring for 2 years. These data suggest that morphologic assessment of CAMLs (growth/hyperploidy) appear to parallel cancer progression, or response to treatment, in multiple solid tumors.

Methods: A prospective multi-institutional study used anonymized peripheral blood samples from 34 cancer patients undergoing therapy [stage I (n=2), II (n=3), III (n=8) & IV (n=21)] with breast (n=10), lung (n=16), & prostate (n=8). Samples were taken prior to therapy (BL), at 1 month (FU1) follow-up and a 3-month (FU2) follow-up, after induction of therapy. Blood was processed by the CellSieve™ microfiltration technique at 4 institutions and stained for cytokeratin 8, 18 and 19, CD14 and CD45. After identification and quantification, CAMLs were measured based on their hyperploidy and cell size.

Results: CAMLs were found in 97% of cancer patients at BL, 97% at FU1 and 91% of FU2. Over the 2-year follow-up, 7 patients showed no signs of clinical disease progression, while 27 patients had observable progression. Of the 7 patients who did not progress, only two had CAMLs of ≥50µm at BL and at FU1, but whose CAMLs shrunk to &lt;50 µm by FU2. Of the 27 patients who progressed, 22 patients had ≥50µm CAMLs at all time points, while 5 patients had small &lt;50µm CAMLs at BL. Interestingly, CAMLs in these 5 patients had enlarged to ≥50µm by the FU2 time point.

Conclusions: We show that increased polynucleation and CAML enlargement indicate shorter progression-free survival in a number of cancer types after baseline. By monitoring CAML changes over time for the 34 individual patients, we demonstrated correlation of ongoing progression, or response, in tumors to the enlargement or shrinkage in CAMLs at follow-up time points from treatment induction. This pilot study suggests that CAMLs have the potential to monitor the progression/regression of malignancy in real time and suggests the need for larger validation studies.

Citation Format: Daniel L. Adams, Raymond Bergan, Martin J. Edelman, Stuart S. Martin, Rena Lapidus, Saranya Chumsri, Cha-Mei Tang, Steven H. Lin. Real-time monitoring of solid tumor progression by circulating stromal cells from early- to late-stage disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1560.

Sequential Tracking of PD-L1 Expression and RAD50 Induction in Circulating Tumor and Stromal Cells of Lung Cancer Patients Undergoing Radiotherapy

Purpose: Evidence suggests that PD-L1 can be induced with radiotherapy and may be an immune escape mechanism in cancer. Monitoring this response is limited, as repetitive biopsies during therapy are impractical, dangerous, and miss tumor stromal cells. Monitoring PD-L1 expression in both circulating tumor cells (CTCs) and circulating stromal cells (CStCs) in blood-based biopsies might be a practical alternative for sequential, noninvasive assessment of changes in tumor and stromal cells.Experimental Design: Peripheral blood was collected before and after radiotherapy from 41 patients with lung cancer, as were primary biopsies. We evaluated the expression of PD-L1 and formation of RAD50 foci in CTCs and a CStC subtype, cancer-associated macrophage-like cells (CAMLs), in response to DNA damage caused by radiotherapy at the tumor site.Results: Only 24% of primary biopsies had sufficient tissue for PD-L1 testing, tested with IHC clones 22c3 and 28-8. A CTC or CAML was detectable in 93% and 100% of samples, prior to and after radiotherapy, respectively. RAD50 foci significantly increased in CTCs (>7×, P < 0.001) and CAMLs (>10×, P = 0.001) after radiotherapy, confirming their origin from the radiated site. PD-L1 expression increased overall, 1.6× in CTCs (P = 0.021) and 1.8× in CAMLs (P = 0.004): however, individual patient PD-L1 expression varied, consistently low/negative (51%), consistently high (17%), or induced (31%).Conclusions: These data suggest that RAD50 foci formation in CTCs and CAMLs may be used to track cells subjected to radiation occurring at primary tumors, and following PD-L1 expression in circulating cells may be used as a surrogate for tracking adaptive changes in immunotherapeutic targets. Clin Cancer Res; 23(19); 5948-58. ©2017 AACR.

Abstract 3798: Multiplex phenotyping of circulating cancer associated macrophage-like cells in patients with solid tumors

Background: Circulating cancer associated macrophage-like cells (CAMLs) are cancer specific giant cells circulating in the blood of patients with solid tumors. Since their discovery, few studies have been done to elucidate their lineage or phenotypic identity. The difficulty in classifying CAMLs is exemplified by their expression of multiple heterogeneous markers that defy conventional identification. Recently, we described a restaining method (QUAS-R) to screen individual cells using an array of up to 15 biomarkers. We used this method to screen CAMLs isolated from 152 cancer patient samples in 4 types of solid tumors to classify CAMLs by phenotypic immunostaining. These data suggest that CAMLs are a morphologically diverse and phenotypically heterogeneous population of cancer specific giant cells with overlapping myeloid, epithelial, and endothelial phenotypes.

Methods: This multi-institutional study used peripheral blood samples from 152 cancer patients (stage I-IV) from breast (n=42), lung (n=39), renal cell carcinoma (36) and prostate (n=35). Blood was processed by the CellSieve™ microfiltration technique at 5 institutions and stained for cytokeratin 8, 18 & 19, EpCAM, and CD45. After identification/imaging, the QUAS-R (Quench, Underivatize, Amine-Strip and Restain) technique was used to quench fluorescence signal of cells and then restain with vimentin/CD146/CD144, CD14/CD11b/CD41, CD11c/CD68/TIE2, or CD34/CD41/CD61. After staining, QUAS-R was again used to remove the fluorescence and samples restained with a third panel. Each patient sample was stained, quenched and restained with the above mentioned panels.

Results: In agreement with a number of studies, CAMLs were found in 86% of cancer patients (n=131/152), with increased detection from stage 1 (71%), followed by stage 2 (94%), stage 3 (88%) to stage 4 (88%). Breast cancer had the most CAMLs per sample (14.1 cells/7.5mL), followed by prostate (6.8), renal cell carcinoma (4.9) and lung (3.2). CD34 was most prevalent, found on 88% of CAMLs, followed by cytokeratin (81%), CD41 (79%), CD61 (78%), CD45 (75%), CD14 (72%), vimentin (63%), EpCAM (56%), CD146 (53%), CD68 (44%), CD11c (38%), TIE-2 (25%) and CD11b (0%). Based on our results, CAMLs seem to express overlapping phenotypes from a variety of lineages i.e. macrophage (CD14/CD68/CD11c), epithelial (cytokeratin/EpCAM), endothelial (CD146/TIE-2) and megakaryocyte (CD41/CD61).

Conclusions: Although identification of CAMLs is straightforward by morphological criteria (size and nuclear profile), their identification and lineage remains undetermined. We report the first mass screening of CAMLs to determine phenotypic expression. These data suggest that CAMLs cannot be grouped into any known cell subtype based on their expression profiles and represent a heterogeneous and variably differentiated population whose biological consequences in cancer remain under investigation.

Citation Format: Daniel L. Adams, R Katherine Alpaugh, Thai H. Ho, Steven H. Lin, Jeffrey R. Marks, Raymond Bergan, Stuart S. Martin, Saranya Chumsri, Cha-Mei Tang, Massimo Cristofanilli. Multiplex phenotyping of circulating cancer associated macrophage-like cells in patients with solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3798. doi:10.1158/1538-7445.AM2017-3798

Abstract 778: Identifying, subtyping and classifying tumor associated circulating endothelial cells in patients with solid tumors

Background: Tumor endothelial cells (ECs) are a population of stromal cells required for tumor growth that cooperate with tumors to form angiogenic structures. In blood, circulating ECs (CECs) are normal constituents of healthy individuals, although a Cancer Associated Vascular Endothelial cell (CAVE) subtype has been observed in cancer patients. The CAVE population has been isolated and identified using their large size or multicellular clustering and a pooled mixture of classical EC markers (i.e. CD31 and CD146). However, there has been no attempt to differentiate CAVEs from the many EC subtypes. This is not surprising as in-depth phenotyping of ECs requires an array of biomarkers that until recently has not been feasible. A multi-phenotypic screening of EC markers was tested on CAVEs from 116 blood samples in 3 types of solid tumors. This data suggests that CAVEs exist as a common and diverse subtype of tumor derived CECs that may express cytokeratin (CK) and various EC biomarkers, correlating to disease stage.

Methods: Peripheral blood samples from 116 cancer patients (stage I-IV) were drawn from 2012-2014 including breast (n=42), lung (n=39) and prostate (n=35), as well as blood from 34 healthy controls. Blood was processed by an established filtration approach, i.e. the CellSieveTM microfiltration technique (Creatv MicroTech), filtering blood by size exclusion and staining cells for CK 8, 18 & 19, EpCAM and CD45. After identification and imaging, the QUAS-R (Quench, Underivatize, Amine-Strip and Restain) technique was used to remove fluorescence signal and restain all cells with CD31, CD146, CD144, & DAPI. After reimaging, QUAS-R was again used to remove fluorescence and restain the cells for CD14, CD105, CD34, & DAPI.

Results: Out of 116 patient samples, we identified CAVEs in 63 patients (54%) based on positivity of CD31, CD144 or CD146, but none were found in healthy controls. CAVEs per 7.5mL sample in patients averaged 5.1 (breast), 5.6 (prostate) and 7.9 (lung). Presence of CAVEs appeared related to stage with 26% in stage 1, 61% in stage 2, 68% in stage 3, and 74% in stage 4 patients. No CAVEs were positive for CD14 or CD45. CD31 was the most present marker, found on 93% of CAVEs, followed by CD144 (85%), CD34 (64%), CD146 (45%), & CD105 (4%). In contrast with the previous study on this topic, CK was found in 67% of CAVEs, but was not a universal marker.

Conclusions: It has been reported that CK+ and CD45- CECs are isolated from the blood of cancer patients in colon and lung cancers, prompting some to classify them as circulating tumor cells. However, subtyping these CECs is incomplete when characterized with only 3-4 biomarkers. A multi-phenotypic subtyping technique was used to properly identify and subtype these CECs in cancer patients. This data suggest that a subset of CECs, e.g. CAVEs, are found in circulation as CK+/CD45-, but exist as a heterogeneous population of cancer specific circulating cells that require further study.

Citation Format: Daniel L. Adams, R. Katherine Alpaugh, Steven H. Lin, Jeffrey R. Marks, Raymond Bergan, Stuart S. Martin, Sarany Chumsri, Massimo Cristofanilli, Cha-Mei Tang, Steingrimur Stefansson. Identifying, subtyping and classifying tumor associated circulating endothelial cells in patients with solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 778. doi:10.1158/1538-7445.AM2017-778

Cancer-associated macrophage-like cells as prognostic indicators of overall survival in a variety of solid malignancies

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Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell subtype commonly found in the peripheral blood of patients in all stages of solid malignancies and in a variety of cancer subtypes. However, while their biological association to cancer is being studied, their clinical utilization as it relates to cancer prognosis has not been evaluated. Methods: A two year prospective study was undertaken to evaluate the relationship of CAMLs and overall survival (OS) in 6 solid tumor types. The single blind multi-institutional study consisted of 269 stage I-IV patients; breast (n = 57), esophageal (n = 21), prostate (n = 43), pancreatic (n = 59), lung (n = 54), and renal cell (n = 35), in treatment (n = 134) and untreated baseline (n = 135). 7.5mL of whole blood was filtered by CellSieve microfiltration assay and CAMLs enumerated, as previously described. Patients were grouped by CAML number ( < 6 or ≥6) and by size ( < 49 or ≥50 µm) to evaluate hazard ratios (HR) by censored univariate & multivariate analysis. Results: CAMLs were identified in 93% of samples, averaging 8.2 CAMLs/7.5mL blood sample, and found in all 6 cancers at baseline and during treatment. Average CAML number was associated with disease stage and CAML positivity was 4.4 & 80% (Stage I), 4.7 & 93% (Stage II), 9.3 & 98% (Stage 3), 12.1 & 97% (Stage IV). Univariate analysis of patients (n = 269) stratified by ≥6 CAMLs had reduced OS (HR = 1.8, 95%CI 1.1-2.9, p = 0.03). Further, CAML size also had reduced OS in patients with ≥50 µm CAMLs (HR = 2.7, 95%CI 1.8-4.0, p < 0.0001). Conclusions: Our data suggests that in solid malignancies, CAML number and size appear to clinically correlate with OS in early and late stage disease. Given these results relating CAMLs with OS, further analysis is warranted to determine if CAMLs can serve as a clinically-relevant blood-based marker.

Enrichment and Molecular Analysis of Breast Cancer Disseminated Tumor Cells from Bone Marrow Using Microfiltration

Purpose

Molecular characterization of disseminated tumor cells (DTCs) in the bone marrow (BM) of breast cancer (BC) patients has been hindered by their rarity. To enrich for these cells using an antigen-independent methodology, we have evaluated a size-based microfiltration device in combination with several downstream biomarker assays.

Methods

BM aspirates were collected from healthy volunteers or BC patients. Healthy BM was mixed with a specified number of BC cells to calculate recovery and fold enrichment by microfiltration. Specimens were pre-filtered using a 70 μm mesh sieve and the effluent filtered through CellSieve microfilters. Captured cells were analyzed by immunocytochemistry (ICC), FISH for HER-2/neu gene amplification status, and RNA in situ hybridization (RISH). Cells eluted from the filter were used for RNA isolation and subsequent qRT-PCR analysis for DTC biomarker gene expression.

Results

Filtering an average of 14×10⁶ nucleated BM cells yielded approximately 17–21×10³ residual BM cells. In the BC cell spiking experiments, an average of 87% (range 84–92%) of tumor cells were recovered with approximately 170- to 400-fold enrichment. Captured BC cells from patients co-stained for cytokeratin and EpCAM, but not CD45 by ICC. RNA yields from 4 ml of patient BM after filtration averaged 135ng per 10 million BM cells filtered with an average RNA Integrity Number (RIN) of 5.3. DTC-associated gene expression was detected by both qRT-PCR and RISH in filtered spiked or BC patient specimens but, not in control filtered normal BM.

Conclusions

We have tested a microfiltration technique for enrichment of BM DTCs. DTC capture efficiency was shown to range from 84.3% to 92.1% with up to 400-fold enrichment using model BC cell lines. In patients, recovered DTCs can be identified and distinguished from normal BM cells using multiple antibody-, DNA-, and RNA-based biomarker assays.

Enhanced adhesion and field emission of CuO nanowires synthesized by simply modified thermal oxidation technique

Metal oxide nanowires (NWs) can be easily grown by the thermal oxidation method, but the low adhesion between the NWs and the substrate restricts their practical applications in functional devices. In this work, the conventional hotplate technique is simply modified by introducing one or two stainless steel plates to supply a more stable oxidation environment, which is found to be beneficial to the growth and adhesion of CuO NWs on the Cu substrate. In detail, the Cu foils were heated on the hotplate directly, on one plate over the hotplate, and between two plates over the hotplate at 400 °C in ambient condition. It is found that the NWs obtained between two plates exhibit large length and diameter with moderate density. The sufficient activated oxygen, stable temperature, and proper temperature gradient configuration caused by the two plates accelerate the formation of CuO NWs, and result in the longest NWs with enhanced adhesion. The grain-boundary diffusion and Kirkendall effect are proposed to explain the mechanism of NWs growth and the formation of cracks. The NWs obtained between two plates also showed the best field emission properties, with lowest turn-on field (5.31 V μm(-1)) and threshold field (9.8 V μm(-1)). Excellent field emission properties and enhanced NW-substrate adhesion indicate that these NW arrays could be potentially used as the cathode of field emission displays.

Abstract 1550: Multi-biomarker subtyping of circulating tumor cells using sequential fluorescence quenching

Background: Circulating tumor cells (CTCs) are rare but clinically valuable indicators of cancer status. However their clinical utility is limited to 2-3 positive fluorescent markers and 1 negative fluorescent marker. By contrast, tissue biopsies allow for numerous subtyping markers, yielding information about the tumor's biology and predicted treatment response. If CTC analysis is to be more useful, it must move beyond 2-3 identification markers. We describe a simple and inexpensive method to capture and identify CTCs using traditional fluorescence biomarkers with repeated restating of 9 unrelated fluorescent antibodies. In this study, we sought to subtype CTCs with the epithelial to mesenchymal-like phenotype (EMTCTCs) from pancreatic cancer samples first identified using a conventional CTC marker panel: Cytokeratin (CK), EpCAM, and CD45. We further subtyped these EMTCTCs with an immunosuppression therapy panel (PD-L1, CXCR4, PD-1) and then with a mesenchymal marker panel (CD14, CD34, Vimentin) to better interrogate the EMT phenotype. Alternative predictive and prognostic biomarkers may also be utilized. The order of staining does not affect the result. Our data demonstrate the ability to sequentially analyze, subtype and track 9 distinct cancer markers on each individual cell.

Methods: We developed a method of fluorescence quenching using cell lines: A2058, MB231, MCF7, HUVEC, and LnCAP. The technique consists of the steps: quench, underivatize, amine strip and restain (“QUASR”). Cells isolated on CellSieveTM microfilters were stained using the CTC marker panel, after which the QUASR protocol was applied and the cells were stained with a second mesenchymal marker panel. After imaging, QUASR was repeated for a third immunotherapy marker panel, and cells imaged a third time. QUASR was then used on 12 pancreatic cancer patient blood samples previously identified with EMTCTCs provided by Medical College of Wisconsin.

Results: No degradation was observed in cell surface, or intracellular markers for the 3 rounds of QUASR. There were 764 EMTCTCs identified as CK+/CD45- in the cancer patient samples, while EpCAM was positive in only 2% of these EMTCTCs. Post quenching, most EMTCTCs had additional mesenchymal phenotypes, i.e. 97% of cells were vimentin+ and 11% were CD34+. Expression of the immunotherapy markers were highly heterogeneous between patients, ranging from 0% to 100% positivity for PD-L1 and from 0% to 90% positivity for CXCR4. None of the CTCs were PD-1+ nor CD14+.

Conclusions: Our data demonstrates that sequential multi-panel restaining of clinically applicable cancer biomarkers can provide a greater amount and broader variety of information from patient blood samples. The ability to analyze CTCs beyond simple enumeration will greatly enhance the clinical utility of blood based biopsies, as patient samples can now be screened for multiple prognostic and predictive biomarkers.

Citation Format: Daniel L. Adams, Susan Tsai, Cha-Mei Tang, Steingrimur Stefansson. Multi-biomarker subtyping of circulating tumor cells using sequential fluorescence quenching. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1550.

Abstract 4990: Sequential tracking of PD-L1 expression and RAD50 induction in CTCs and circulating stromal cells of lung cancer patients during treatment with radiotherapy

Background: PD-L1 expression can be induced by radiotherapy (RT) and may be an immune escape mechanism after RT, and has the potential to predict for responsiveness to immune checkpoint blockade immunotherapy. However, repetitive biopsies for monitoring PD-L1 expression in tumor and/or stroma are not feasible. Sequential assessment of PD-L1 expression on cancer associated circulating cells during treatment may be a way to measure the efficacy of combining RT and immunotherapy. RAD50 is a DNA repair gene that can be used in tracking tumor cell response to radiation. We therefore evaluated PD-L1 expression and RAD50 induction in CTCs and Cancer Associated Macrophage-Like Cells (CAMLs) in lung cancer patients (pts) before and during RT to track expression changes of these markers.

Methods: Twenty-nine pts with stage I-IV lung cancer were included in this prospective pilot study. Four pts received radiation therapy for stage I disease and 25 other pts received chemoradiation for stage II-IV disease. A baseline blood sample (7.5 ml) was drawn prior to the start of RT (T0), and a second blood sample was drawn at a treatment visit during RT (T1) for a total of 58 samples. Blood was processed using CellSieve™ microfiltration (Creatv MicroTech), stained for cytokeratin 8, 18 & 19 and CD45, and imaged. Using the QUASR (Quench, Underivatize, Amine-Strip and Restain) technique to remove fluoresce signal, all cells were restained for RAD50-AlexaFluor550 and PD-L1-AlexaFluor 488, along with DAPI nuclear stain. The RAD50 foci were quantified within nuclear regions and PD-L1 pixel intensity measured and grouped into 4 IHC groups: 0-negative (pixel average 0-215), 1-low (pixel average 216-300), 2-medium (pixel average 301-750), and 3-high (pixel average 751+).

Results: There was at least one cytokeratin positive cell (i.e. CTC or CAMLs) found in all but 2 samples (97%). CTCs were found in 69% of T0 and 72% of T1 samples, and CAMLs in 79% of T0 and 97% of T1 samples. PD-L1 expression ranged from 34-2552 pixel intensity, with an average of 285 at T0 and 525 at T1 (p = 0.07). Interestingly, 9 pts had no PD-L1 expression at T0 but an increase to 2 to 3+ at T1, 12 pts with low/no PD-L1 expression remained low at T1, and 8 pts had high PD-L1 expression that remained high or decreased at T1. RAD50 foci ranged from 0-16 per cell, with an average of 0.56 at T0 that increased to 4.68 at T1 (p&lt;0.001) during radiotherapy. There was no correlation between RAD50 induction and PD-L1 expression.

Conclusions PD-L1 expression and RAD 50 foci were quantifiable in both CTCs and CAMLs, and a correlative response to radiotherapy +/- chemotherapy was quantified. This data suggests that sequential tracking of CTCs and immune-related cells from the primary lung tumor is feasible using microfiltration and may potentially serve as a predictive biomarker for cancer therapy sensitivity.

Citation Format: Daniel L. Adams, Martin J. Edelman, Penny Fang, Wen Jiang, Jianzhong He, Ting Xu, Hui Gao, James M. Reuben, Yawei Qiao, Steven Hahn, Ritsuko Komaki, Zhongxing Liao, Cha-Mei Tang, Steven H. Lin. Sequential tracking of PD-L1 expression and RAD50 induction in CTCs and circulating stromal cells of lung cancer patients during treatment with radiotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4990.

Detection of tumor-associated cells in cryopreserved peripheral blood mononuclear cell samples for retrospective analysis

Background

Cryopreserved peripheral blood mononuclear cells (PBMCs) are commonly collected in biobanks. However, little data exist regarding the preservation of tumor-associated cells in cryopreserved collections. The objective of this study was to determine the feasibility of using the CellSieve™ microfiltration assay for the isolation of circulating tumor cells (CTCs) and circulating cancer-associated macrophage-like cells (CAMLs) from cryopreserved PBMC samples.

Methods

Blood samples spiked with breast (MCF-7), prostate (PC-3), and renal (786-O) cancer cell lines were used to establish analytical accuracy, efficiency, and reproducibility after cryopreservation. The spiked samples were processed through Ficoll separation, and cryopreservation was followed by thawing and microfiltration.

Results

MCF-7 cells were successfully retrieved with recovery efficiencies of 90.5 % without cryopreservation and 87.8 and 89.0 %, respectively, on day 7 and day 66 following cryopreservation. The corresponding recovery efficiencies of PC-3 cells were 83.3 % without cryopreservation and 85.3 and 84.7 %, respectively, after cryopreservation. Recovery efficiencies of 786-O cells were 92.7 % without cryopreservation, and 82.7 and 81.3 %, respectively, after cryopreservation. The recovered cells retained the morphologic characteristics and immunohistochemical markers that had been observed before freezing. The protocols were further validated by quantitation of CAMLs in blood samples from two patients with renal cell carcinoma (RCC). The recovery rates of CTCs and CAMLs from cryopreserved samples were not statistically significant different (P > 0.05) from matched fresh samples.

Conclusions

To our knowledge, this is the first report that CAMLs could be cryopreserved and analyzed after thawing with microfiltration technology. The application of microfiltration technology to cryopreserved samples will enable much greater retrospective study of cancer patients in relation to long-term outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0953-2) contains supplementary material, which is available to authorized users.

Circulating Cancer-Associated Macrophage-Like Cells Differentiate Malignant Breast Cancer and Benign Breast Conditions

BACKGROUND

Blood-based testing can be used as a noninvasive method to recover and analyze circulating tumor-derived cells for clinical use. Circulating cancer-associated macrophage-like cells (CAML) are specialized myeloid cells found in peripheral blood and associated with the presence of solid malignancies. We measured CAMLs prospectively in peripheral blood to ascertain their prevalence, specificity, and sensitivity in relation to breast disease status at clinical presentation.

METHODS

We report on two related but separate studies: 1) CellSieve microfilters were used to isolate CAMLs from blood samples of patients with known malignant disease (n = 41). Prevalence and specificity was compared against healthy volunteers (n = 16). 2) A follow-up double-blind pilot study was conducted on women (n = 41) undergoing core-needle biopsy to diagnose suspicious breast masses.

RESULTS

CAMLs were found in 93% of known malignant patients (n = 38/41), averaging 19.4 cells per sample, but none in the healthy controls. In subjects undergoing core biopsy for initial diagnosis, CAMLs were found in 88% of subjects with invasive carcinoma (n = 15/17) and 26% with benign breast conditions (n = 5/19).

CONCLUSION

These preliminary pilot studies suggest that the presence of CAMLs may differentiate patients with malignant disease, benign breast conditions, and healthy individuals.

IMPACT

We supply evidence that this previously unidentified circulating stromal cell may have utility as a screening tool to detect breast cancer in various malignancies, irrespective of disease stage. Cancer Epidemiol Biomarkers Prev; 25(7); 1037-42. ©2016 AACR.

Mitosis in circulating tumor cells stratifies highly aggressive breast carcinomas

Background

Enumeration of circulating tumor cells (CTCs) isolated from the peripheral blood of breast cancer patients holds promise as a clinically relevant, minimally invasive diagnostic test. However, CTC utility has been limited as a prognostic indicator of survival by the inability to stratify patients beyond general enumeration. In comparison, histological biopsy examinations remain the standard method for confirming malignancy and grading malignant cells, allowing for cancer identification and then assessing patient cohorts for prognostic and predictive value. Typically, CTC identification relies on immunofluorescent staining assessed as absent/present, which is somewhat subjective and limited in its ability to characterize these cells. In contrast, the physical features used in histological cytology comprise the gold standard method used to identify and preliminarily characterize the cancer cells. Here, we superimpose the methods, cytologically subtyping CTCs labeled with immunohistochemical fluorescence stains to improve their prognostic value in relation to survival.

Methods

In this single-blind prospective pilot study, we tracked 36 patients with late-stage breast cancer over 24 months to compare overall survival between simple CTC enumeration and subtyping mitotic CTCs. A power analysis (1-β = 0. 9, α = 0.05) determined that a pilot size of 30 patients was sufficient to stratify this patient cohort; 36 in total were enrolled.

Results

Our results confirmed that CTC number is a prognostic indicator of patient survival, with a hazard ratio 5.2, p = 0.005 (95 % CI 1.6–16.5). However, by simply subtyping the same population based on CTCs in cytological mitosis, the hazard ratio increased dramatically to 11.1, p < 0.001 (95 % CI 3.1–39.7).

Conclusions

Our data suggest that (1) mitotic CTCs are relativity common in aggressive late-stage breast cancer, (2) mitotic CTCs may significantly correlate with shortened overall survival, and (3) larger and more defined patient cohort studies are clearly called for based on this initial pilot study.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0706-4) contains supplementary material, which is available to authorized users.

Polymer microfilters with nanostructured surfaces for the culture of circulating cancer cells

There is a critical need to improve the accuracy of drug screening and testing through the development of in vitro culture systems that more effectively mimic the in vivo environment. Surface topographical features on the nanoscale level, in short nanotopography, effect the cell growth patterns, and hence affect cell function in culture. We report the preliminary results on the fabrication, and subsequent cellular growth, of nanoscale surface topography on polymer microfilters using cell lines as a precursor to circulating tumor cells (CTCs). To create various nanoscale features on the microfilter surface, we used reactive ion etching (RIE) with and without an etching mask. An anodized aluminum oxide (AAO) membrane fabricated directly on the polymer surface served as an etching mask. Polymer filters with a variety of modified surfaces were used to compare the effects on the culture of cancer cell lines in blank culture wells, with untreated microfilters or with RIE-treated microfilters. We then report the differences of cell shape, phenotype and growth patterns of bladder and glioblastoma cancer cell lines after isolation on the various types of material modifications. Our data suggest that RIE modified polymer filters can isolate model cell lines while retaining ell viability, and that the RIE filter modification allows T24 monolayering cells to proliferate as a structured cluster.

Abstract B37: Detection of sarcoma circulating tumor cells using a size based microfiltration device

The inability to effectively treat hematogenous metastasis remains the largest challenge of sarcoma therapy. The ability to isolate, quantify, and study circulating tumor cells (CTC) in sarcomas has the potential to enhance our understanding of the biology of metastasis, altering the way we treat patients with high grade sarcomas. Using a size based filtration device, CellSieve™, we were able to successfully identify and quantify CTC in a metastatic xenograft model as well as in blood samples from patients with high grade sarcomas. In mice, we utilized our orthotopic implantation/amputation model of metastasis. Using a TdTomato-expressing Ewing sarcoma cell line and a cocktail of fluorescently labeled antibodies to vimentin and CD45, we were able to detect both CTC and circulating tumor clusters (CTCL) in mice with growing tumors and with metastatic disease, but not in mice immediately post-amputation. These experiments were augmented with samples collected from patients with high grade sarcomas. In 18 samples from 15 patients, we were able to identify both CTC and CTCL. Furthermore, we were also able to validate the presence of CTC by PCR amplification of sarcoma-associated chromosomal translocations. Future work will use this system to explore the biology of sarcoma metastasis by studying genetic, transcriptional, and epigenetic characteristics of CTC and CTCL and comparing these cells to those in the bulk primary tumor. We will also further explore the possibility that CTC and/or CTCL might serve as a biomarker of disease burden, response to treatment, or metastatic risk.

Citation Format: Masanori Hayashi, Peixuan Zhu, Catherine M. Albert, Diana Steppan, Gregory McCarty, Kyle W. Jackson, Cha-Mei Tang, David M. Loeb. Detection of sarcoma circulating tumor cells using a size based microfiltration device. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B37.

Precision Microfilters as an all in one System for Multiplex Analysis of Circulating Tumor Cells

Enumeration of circulating tumor cells (CTCs) from cancer patient blood is an established diagnostic assay used to evaluate patient status as a singleplex test. However, in the coming age of personalized medicine, multiplex analysis of patient CTCs, including proteomic and genomic techniques, will have to be integrated with CTC isolation platform technologies. Advancements in microfabrication have demonstrated that CTCs can be isolated and analyzed using microfluidic lab-on-a-chip devices. However, to date, most microfluidic devices are either still in the development phase, not applicable to all clinical tests, or are not commercially available. To overcome these discrepancies, we describe an all-in-one device for the isolation and multiplexing of clinically applicable CTC assays. Microfilters present an ideal lab-on-a-chip platform for analysis of CTCs as non-toxic and inert materials allow for a multitude of tests from cell growth through clinical staining techniques, all without background interference. Lithographically fabricated microfilters, can be made with high porosity, precise pore dimensions, arrayed pore distribution, and optimized for CTC size-based isolation. In this study we describe microfilter use in isolation and in situ analysis of CTCs using multiple sequential techniques including culture, FISH, histopathological analysis, H&E staining, photobleaching and re-staining. Further, as a proof of principle, we then describe the ability to quantitatively release patient derived CTCS from the microfilters for potential use in downstream genomic/proteomic analysis.