The Great Immune Escape: Understanding the Divergent Immune Response in Breast Cancer Subtypes

Breast cancer, the most common type of cancer affecting women, encompasses a collection of histologic (mainly ductal and lobular) and molecular subtypes exhibiting diverse clinical presentation, disease trajectories, treatment options, and outcomes. Immunotherapy has revolutionized treatment for some solid tumors but has shown limited promise for breast cancers. In this review, we summarize recent advances in our understanding of the complex interactions between tumor and immune cells in subtypes of breast cancer at the cellular and microenvironmental levels. We aim to provide a perspective on opportunities for future immunotherapy agents tailored to specific features of each subtype of breast cancer.

SIGNIFICANCE

Although there are currently over 200 ongoing clinical trials testing immunotherapeutics, such as immune-checkpoint blockade agents, these are largely restricted to the triple-negative and HER2+ subtypes and primarily focus on T cells. With the rapid expansion of new in vitro, in vivo, and clinical data, it is critical to identify and highlight the challenges and opportunities unique for each breast cancer subtype to drive the next generation of treatments that harness the immune system.

Abstract A18: GRK2, an inhibitor of MALT1-dependent oncogenic signaling, is downregulated by microRNA in ABC-DLBCL

Introduction and Background: The “CBM” complex is composed of the scaffolding protein CARMA1, the adaptor protein BCL10, and the effector protein MALT1. This complex performs multiple pivotal functions as a mediator of antigen receptor-dependent induction of the NF-κB transcription factor and subsequent lymphocyte activation. The key downstream effector of the CBM complex, MALT1, regulates downstream signaling via both scaffolding and proteolytic functions. Inappropriate activation of MALT1, which can result from somatic gain-of-function mutation in upstream regulators of MALT1 or chromosomal translocation involving the MALT1 gene, underlies the pathogenesis of a variety of lymphoid malignancies including activated B cell type-diffuse large B cell lymphoma (ABC-DLBCL) and mucosa associated lymphoid tissue (MALT) lymphoma. We recently discovered that G-protein-coupled receptor kinase 2 (GRK2) binds to MALT1 and inhibits MALT1 scaffold and proteolytic activities. Further, we found that knockdown of GRK2 in ABC-DLBCL enhances tumor growth in vivo, suggesting that GRK2 may act as a tumor suppressor in MALT1-dependent lymphomas. Interestingly, we found that GRK2 mRNA levels are markedly lower in a subset of DLBCL cases in comparison to normal B-cell controls and that lower GRK2 level is associated with reduced survival in ABC-DLBCL patients. We thus sought to investigate how GRK2 expression is regulated in ABC-DLBCL. Methods and Results: We first investigated whether mutations/deletions in the ADRBK1 gene (GRK2) account for the lower levels of GRK2 expression in a subset of DLBCL cases. Only one mutation among 6 published DLBCL sequencing datasets (334 cases total) was identified. We next considered that other mechanisms, such as regulation by microRNA (miRNA), could play a role in downregulating GRK2. Using DICER-deficient HEK 293T cells, we demonstrated that GRK2 protein level significantly increases when miRNA processing is impaired. We then used mirDIP, a microRNA Data Integration Portal, to screen for candidate miRNAs predicted to target the 3’UTR of GRK2. We identified 4 top candidate hits, 2 of which were also identified in bioinformatic analysis as miRNA whose level inversely correlates with GRK2 mRNA level in ABC-DLBCL patient tumor specimens. Using a GRK2 3’ UTR reporter system, we confirmed direct targeting of GRK2 by these miRNAs. Next, we generated stable ABC-DLBCL cell lines (TMD8, OCI-Ly3) overexpressing candidate miRNAs. Our results demonstrate that candidate miRNA overexpression results in reduced GRK2 expression and increased MALT1 scaffolding and proteolytic activities, NF-κB transcriptional activity and ABC-DLBCL cell proliferation. Conclusions: Together, our data suggest that miRNAs down-regulate expression of GRK2 in ABC-DLBCL which in turn enhances MALT1 scaffolding and proteolytic activities, leading to increased tumor cell proliferation. Future studies are aimed at identifying potential miRNA inhibitors which enhance GRK2 expression and thereby suppress MALT1 pro-tumorigenic activity in ABC-DLBCL.

Citation Format: Jing Cheng, Mei Smyers, Matt Trotta, Neil M Carleton, Lisa M Maurer, Peter C Lucas, Linda M McAllister-Lucas. GRK2, an inhibitor of MALT1-dependent oncogenic signaling, is downregulated by microRNA in ABC-DLBCL [abstract]. In: Proceedings of the Third AACR International Meeting: Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2022 Jun 23-26; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2022;3(5_Suppl):Abstract nr A18.

Association Between Portal Vein Thrombosis and Pouchitis in Patients with Ulcerative Colitis

BACKGROUND

Pouchitis is the most common long-term complication in patients requiring colectomy ileal pouch-anal anastomosis with medically refractory ulcerative colitis or colitis-associated neoplasia. A previous small case series suggests associated between portal vein thrombosis (PVT) and ischemic pouchitis.

AIM

To evaluate the association between PVT and other demographic and clinical factors and pouchitis.

METHODS

We used Explorys Inc., a population-based database, to search medical records between 1999 and 2020 with SNOMED-CT code criteria for "construction of pouch" and "ileal pouchitis." Patients with pouchitis were compared to those with previous pouch construction without pouchitis. Factors associated with pouchitis identified with univariable analysis were introduced into a multivariable model. A post hoc analysis further stratified demographical findings of the association between PVT and pouchitis.

RESULTS

We identified 7900 patients with ileal pouchitis (7.5%) and 97,510 with pouch construction without pouchitis. In multivariate binary logistic regression, adjusted odds ratio (aOR) for the risk of pouchitis in patients with PVT was 10.78 (95% confidence interval [CI] 7.04-16.49, P < 0.001). Other significant factors associated with pouchitis included male gender (aOR 1.11, 95% CI 1.02-1.21, P = 0.018), deep vein thrombosis (aOR 1.46, 95% CI 1.23-1.72, P < 0.001), and the use of non-steroidal anti-inflammatory drugs (aOR 1.37, 95% CI 1.28-1.45, P < 0.001). Smoking was a protective factor (aOR 0.30, 95% CI 0.33-0.36, P < 0.001). Further sub-analysis showed a higher prevalence of younger patients with PVT and pouchitis.

CONCLUSIONS

We report PVT as an independent risk factor associated with pouchitis. Our findings support that PVT is a potentially manageable perioperative complication, and intervention may reduce the risk of pouchitis.

MALT1 is a Targetable Driver of Epithelial-to-Mesenchymal Transition in Claudin-low, Triple-Negative Breast Cancer

MALT1 is the effector protein of the CARMA/Bcl10/MALT1 (CBM) signalosome, a multi-protein complex that drives pro-inflammatory signaling pathways downstream of a diverse set of receptors. While CBM activity is best known for its role in immune cells, emerging evidence suggests that it plays a key role in the pathogenesis of solid tumors, where it can be activated by selected G protein-coupled receptors (GPCRs). Here, we demonstrated that overexpression of GPCRs implicated in breast cancer pathogenesis, specifically the receptors for Angiotensin II and thrombin (AT1R and PAR1), drove a strong epithelial-to-mesenchymal transition (EMT) program in breast cancer cells that is characteristic of claudin-low, triple-negative breast cancer (TNBC). In concert, MALT1 was activated in these cells and contributed to the dramatic EMT phenotypic changes through regulation of master EMT transcription factors including Snail and ZEB1. Importantly, blocking MALT1 signaling, through either siRNA-mediated depletion of MALT1 protein or pharmacologic inhibition of its activity, was effective at partially reversing the molecular and phenotypic indicators of EMT. Treatment of mice with mepazine, a pharmacologic MALT1 inhibitor, reduced growth of PAR1+, MDA-MB-231 xenografts and had an even more dramatic effect in reducing the burden of metastatic disease. These findings highlight MALT1 as an attractive therapeutic target for claudin-low TNBCs harboring overexpression of one or more selected GPCRs. Implications: This study nominates a GPCR/MALT1 signaling axis as a pathway that can be pharmaceutically targeted to abrogate EMT and metastatic progression in TNBC, an aggressive form of breast cancer that currently lacks targeted therapies.

Combination of polycarboxybetaine coating and factor XII inhibitor reduces clot formation while preserving normal tissue coagulation during extracorporeal life support

Blood contact with high surface area medical devices, such as dialysis and extracorporeal life support (ECLS), induces rapid surface coagulation. Systemic anticoagulation, such as heparin, is thus necessary to slow clot formation, but some patients suffer from bleeding complications. Both problems might be reduced by 1) replacing heparin anticoagulation with artificial surface inhibition of the protein adsorption that initiates coagulation and 2) selective inhibition of the intrinsic branch of the coagulation cascade. This approach was evaluated by comparing clot formation and bleeding times during short-term ECLS using zwitterionic polycarboxybetaine (PCB) surface coatings combined with either a potent, selective, bicyclic peptide inhibitor of activated Factor XII (FXII900) or standard heparin anticoagulation. Rabbits underwent venovenous ECLS with small sham oxygenators for 60 min using three means of anticoagulation (n = 4 ea): (1) PCB coating + FXII900 infusion, (2) PCB coating + heparin infusion with an activated clotting time of 220-300s, and (3) heparin infusion alone. Sham oxygenator blood clot weights in the PCB + FXII900 and PCB + heparin groups were 4% and 25% of that in the heparin group (p < 10^-6 and p < 10^-5), respectively. At the same time, the bleeding time remained normal in the PCB + FXII900 group (2.4 ± 0.2 min) but increased to 4.8 ± 0.5 and 5.1 ± 0.7 min in the PCB + heparin and heparin alone groups (p < 10^-4 and 0.01). Sham oxygenator blood flow resistance was significantly lower in the PCB + FXII900 and PCB + heparin groups than in the heparin only group (p < 10^-6 and 10^-5). These results were confirmed by gross and scanning electron microscopy (SEM) images and fibrinopeptide A (FPA) concentrations. Thus, the combined use of PCB coating and FXII900 markedly reduced sham oxygenator coagulation and tissue bleeding times versus the clinical standard of heparin anticoagulation and is a promising anticoagulation method for clinical ECLS.

Abstract PS1-10: Outcomes after sentinel lymph node biopsy and radiation therapy in women over 70 years old with ER+, HER2-, clinically node negative breast cancer

Overtreatment of early-stage breast cancer with favorable tumor biology in elderly patients can result in higher rates of complications and morbidities without impacting survival. Guidelines directed towards deimplementation of sentinel lymph node biopsy (SLNB) (Choosing Wisely) and radiation therapy (RT) (National Comprehensive Cancer Network) have been recommended. We sought to describe rates and impact on disease recurrence and survival of SLNB and RT in elderly patients with early breast cancer. Patient data were obtained from the cancer registry and electronic health record from University of Pittsburgh Medical Center, multicenter, single health care system. Consecutive female patients aged ≥ 70 with ER+, HER2- clinically node-negative breast cancer within a health care system from 2010 to 2018 were identified. Rates and patient characteristics associated with receipt of SLNB and RT, as well as local recurrence free survival (LRFS) and disease-free survival (DFS) were compared for patients that were diagnosed between 2010 and 2014 to allow for adequate follow up time. Cox proportional hazards regression was used to estimate hazard ratios (HRs) of mortality. Among 3,361 identified women, 2,195 (65.3%) received SLNB and 1,828 (54.4%) received RT. Rates of SLNB steadily increased (1.0% per year); this trend persisted in 2017 and 2018, even after the Society of Surgical Oncology adopted the Choosing Wisely Guidelines in 2016. During the same time period, rates of RT declined (3.4% per year). To examine outcomes, we limited the analysis to 2109 cases from 2010-2014; median (IQR) follow up time was 4.1 (2.5-5.7) years. Median (IQR) age was 77 (73-82) years. 1373 (65.1%) received SLNB and 1,219 (57.8%) received RT. Patients receiving SLNB were younger (P &lt; 0.001) with smaller (P &lt; 0.0001) and lower stage (P &lt; 0.0001) tumors. They had fewer comorbidities (P &lt; 0.001), longer follow-up times (P &lt; 0.001), were less likely on Medicaid/Medicare (P = 0.0091), and were more often seen at an academic center (P &lt; 0.0001). There was no difference in grade between those that did and did not receive SLNB (P = 0.31) and those that did and did not receive RT (P = 0.13). Multivariate cox proportional hazard analysis showed no effect of SLNB on LRFS (HR = 1.17, 95% CI 0.29-4.75, P = 0.83) or DFS (HR = 0.90, 95% CI 0.44-1.83, P = 0.77). Log rank test showed no difference in 5-year LRFS (P = 0.78) between patients who received (98.5%, 95% CI 97.7%-99.7%) and did not receive (98.1%, 95% CI 96.7%-99.5%) SLNB, but an increase was seen with 5-year DFS (P = 0.023), with 96.2% (95% CI 95.0%-97.4%) of patients disease-free among those who did receive SLNB vs. 93.0% (95% CI 90.6%-95.4%) with no SLNB. Multivariate cox proportional hazard analysis showed that RT was associated with improved LRFS (HR = 0.13, 95% CI 0.03-0.51, P &lt; 0.01) and DFS (HR = 0.32, 95% CI 0.15-0.68, P &lt; 0.01). Log rank test showed a difference in 5-year LRFS (P &lt; 0.0001) for those who received RT (99.4%, 95% CI 98.8%-100%) against those who did not (96.5%, 95% CI 95.0%-98.1%), and a similar difference in 5-year DFS (P &lt; 0.0001) in patients who did (97.0%, 95% CI 95.8%-98.1%) and did not (92.4%, 95% CI 90.2%-94.7%) receive RT. Lower age (OR = 0.89, 95% CI 0.87-0.92) and comorbidities (OR = 0.79, 95% CI 0.66-0.94) were associated with receipt of SLNB, while only age (OR = 0.91, 95% CI 0.88-0.94) was associated with receipt of RT.

We conclude that receipt of SLNB has no impact upon DFS or LRFS. This data supports deimplementation of SLNB for this patient population. Receipt of RT is important for controlling locoregional recurrence, supporting use of RT in this patient cohort.

Citation Format: Priscilla F McAuliffe, Neil M Carleton, Jian Zou, Yusi Fang, Stephen E Koscumb, Osama Shah, Fangyuan Chen, Sushil Beriwal, Emilia J Diego, Adam M Brufsky, Steffi Oesterreich, Steve D Shapiro, Robert Ferris, Leisha A Emens, George Tseng, Oscar C Marroquin, Adrian V Lee. Outcomes after sentinel lymph node biopsy and radiation therapy in women over 70 years old with ER+, HER2-, clinically node negative 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 PS1-10.

Characterization of RNA-Binding Motif 3 (RBM3) Protein Levels and Nuclear Architecture Changes in Aggressive and Recurrent Prostate Cancer

Background

The RNA-binding motif protein 3 (RBM3) has been shown to be up-regulated in several types of cancer, including prostate cancer (PCa), compared to normal tissues. Increased RBM3 nuclear expression has been linked to improved clinical outcomes.

Aims

Given that RBM3 has been hypothesized to play a role in critical nuclear functions such as chromatin remodeling, DNA damage response, and other post-transcriptional processes, we sought to: (1) quantify RBM3 protein levels in archival PCa samples; (2) develop a nuclear morphometric model to determine if measures of RBM3 protein levels and nuclear features could be used to predict disease aggressiveness and biochemical recurrence.

Methods & Results

This study utilized two tissue microarrays (TMAs) stained for RBM3 that included 80 total cases of PCa stratified by Gleason score. A software-mediated image processing algorithm identified RBM3-positive cancerous nuclei in the TMA samples and calculated twenty-two features quantifying RBM3 expression and nuclear architecture. Multivariate logistic regression (MLR) modeling was performed to determine if RBM3 levels and nuclear structural changes could predict PCa aggressiveness and biochemical recurrence (BCR). Leave-one-out cross validation (LOOCV) was used to provide insight on how the predictive capabilities of the feature set might behave with respect to an independent patient cohort to address issues such as model overfitting. RBM3 expression was found to be significantly downregulated in highly aggressive GS ≥ 8 PCa samples compared to other Gleason scores (P < 0.0001) and significantly down-regulated in recurrent PCa samples compared to non-recurrent samples (P = 0.0377). An eleven-feature nuclear morphometric MLR model accurately identified aggressive PCa, yielding a receiver operating characteristic area under the curve (ROC-AUC) of 0.90 (P < 0.0001) in the raw data set and 0.77 (95% CI: 0.83-0.97) for LOOCV testing. The same eleven-feature model was then used to predict recurrence, yielding a ROC-AUC of 0.92 (P = 0.0004) in the raw data set and 0.76 (95% CI: 0.64-0.87) for LOOCV testing.

Conclusions

The RBM3 biomarker alone is a strong prognostic marker for the prediction of aggressive PCa and biochemical recurrence. Further, RBM3 appears to be down-regulated in aggressive and recurrent tumors.

Zwitterionic poly-carboxybetaine coating reduces artificial lung thrombosis in sheep and rabbits

Current artificial lungs fail in 1-4 weeks due to surface-induced thrombosis. Biomaterial coatings may be applied to anticoagulate artificial surfaces, but none have shown marked long-term effectiveness. Poly-carboxybetaine (pCB) coatings have shown promising results in reducing protein and platelet-fouling in vitro. However, in vivo hemocompatibility remains to be investigated. Thus, three different pCB-grafting approaches to artificial lung surfaces were first investigated: 1) graft-to approach using 3,4-dihydroxyphenylalanine (DOPA) conjugated with pCB (DOPA-pCB); 2) graft-from approach using the Activators ReGenerated by Electron Transfer method of atom transfer radical polymerization (ARGET-ATRP); and 3) graft-to approach using pCB randomly copolymerized with hydrophobic moieties. One device coated with each of these methods and one uncoated device were attached in parallel within a veno-venous sheep extracorporeal circuit with no continuous anticoagulation (N = 5 circuits). The DOPA-pCB approach showed the least increase in blood flow resistance and the lowest incidence of device failure over 36-hours. Next, we further investigated the impact of tip-to-tip DOPA-pCB coating in a 4-hour rabbit study with veno-venous micro-artificial lung circuit at a higher activated clotting time of 220-300 s (N ≥ 5). Here, DOPA-pCB reduced fibrin formation (p = 0.06) and gross thrombus formation by 59% (p < 0.05). Therefore, DOPA-pCB is a promising material for improving the anticoagulation of artificial lungs. STATEMENT OF SIGNIFICANCE: Chronic lung diseases lead to 168,000 deaths each year in America, but only 2300 lung transplantations happen each year. Hollow fiber membrane oxygenators are clinically used as artificial lungs to provide respiratory support for patients, but their long-term viability is hindered by surface-induced clot formation that leads to premature device failure. Among different coatings investigated for blood-contacting applications, poly-carboxybetaine (pCB) coatings have shown remarkable reduction in protein adsorption in vitro. However, their efficacy in vivo remains unclear. This is the first work that investigates various pCB-coating methods on artificial lung surfaces and their biocompatibility in sheep and rabbit studies. This work highlights the promise of applying pCB coatings on artificial lungs to extend its durability and enable long-term respiratory support for lung disease patients.

Advances in the computational and molecular understanding of the prostate cancer cell nucleus

Nuclear alterations are a hallmark of many types of cancers, including prostate cancer (PCa). Recent evidence shows that subvisual changes, ones that may not be visually perceptible to a pathologist, to the nucleus and its ultrastructural components can precede visual histopathological recognition of cancer. Alterations to nuclear features, such as nuclear size and shape, texture, and spatial architecture, reflect the complex molecular-level changes that occur during oncogenesis. Quantitative nuclear morphometry, a field that uses computational approaches to identify and quantify malignancy-induced nuclear changes, can enable a detailed and objective analysis of the PCa cell nucleus. Recent advances in machine learning-based approaches can now automatically mine data related to these changes to aid in the diagnosis, decision making, and prediction of PCa prognoses. In this review, we use PCa as a case study to connect the molecular-level mechanisms that underlie these nuclear changes to the machine learning computational approaches, bridging the gap between the clinical and computational understanding of PCa. First, we will discuss recent developments to our understanding of the molecular events that drive nuclear alterations in the context of PCa: the role of the nuclear matrix and lamina in size and shape changes, the role of 3-dimensional chromatin organization and epigenetic modifications in textural changes, and the role of the tumor microenvironment in altering nuclear spatial topology. We will then discuss the advances in the applications of machine learning algorithms to automatically segment nuclei in prostate histopathological images, extract nuclear features to aid in diagnostic decision making, and predict potential outcomes, such as biochemical recurrence and survival. Finally, we will discuss the challenges and opportunities associated with translation of the quantitative nuclear morphometry methodology into the clinical space. Ultimately, accurate identification and quantification of nuclear alterations can contribute to the field of nucleomics and has applications for computationally driven precision oncologic patient care.

PBOV1 as a potential biomarker for more advanced prostate cancer based on protein and digital histomorphometric analysis

BACKGROUND

There are few tissue-based biomarkers that can accurately predict prostate cancer (PCa) progression and aggressiveness. We sought to evaluate the clinical utility of prostate and breast overexpressed 1 (PBOV1) as a potential PCa biomarker.

METHODS

Patient tumor samples were designated by Grade Groups using the 2014 Gleason grading system. Primary radical prostatectomy tumors were obtained from 48 patients and evaluated for PBOV1 levels using Western blot analysis in matched cancer and benign cancer-adjacent regions. Immunohistochemical evaluation of PBOV1 was subsequently performed in 80 cancer and 80 benign cancer-adjacent patient samples across two tissue microarrays (TMAs) to verify protein levels in epithelial tissue and to assess correlation between PBOV1 proteins and nuclear architectural changes in PCa cells. Digital histomorphometric analysis was used to track 22 parameters that characterized nuclear changes in PBOV1-stained cells. Using a training and test set for validation, multivariate logistic regression (MLR) models were used to identify significant nuclear parameters that distinguish Grade Group 3 and above PCa from Grade Group 1 and 2 PCa regions.

RESULTS

PBOV1 protein levels were increased in tumors from Grade Group 3 and above (GS 4 + 3 and ≥ 8) regions versus Grade Groups 1 and 2 (GS 3 + 3 and 3 + 4) regions (P = 0.005) as assessed by densitometry of immunoblots. Additionally, by immunoblotting, PBOV1 protein levels differed significantly between Grade Group 2 (GS 3 + 4) and Grade Group 3 (GS 4 + 3) PCa samples (P = 0.028). In the immunohistochemical analysis, measures of PBOV1 staining intensity strongly correlated with nuclear alterations in cancer cells. An MLR model retaining eight parameters describing PBOV1 staining intensity and nuclear architecture discriminated Grade Group 3 and above PCa from Grade Group 1 and 2 PCa and benign cancer-adjacent regions with a ROC-AUC of 0.90 and 0.80, respectively, in training and test sets.

CONCLUSIONS

Our study demonstrates that the PBOV1 protein could be used to discriminate Grade Group 3 and above PCa. Additionally, the PBOV1 protein could be involved in modulating changes to the nuclear architecture of PCa cells. Confirmatory studies are warranted in an independent population for further validation.