Tumor heterogeneity and clinically invisible micrometastases in metastatic breast cancer-a call for enhanced surveillance strategies

The biology of metastatic breast cancer (MBC) is understudied, primarily due to the difficulty of procuring multiple samples from patients with oligometastatic breast cancer. We developed a rapid postmortem tissue procurement program that allows the collection and analysis of numerous metastatic lesions, subclinical locations, and potential pre-metastatic niches that fall within this scope. We conducted a rapid postmortem tissue collection study on 9 patients with MBC. Patients and their families consented to donate tissues immediately after death in an IRB-approved study. Various disease subtypes, progression histories, organ involvement, and final causes of death are reported. In patients with hormone receptor-positive (HR+) disease, estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki-67 expression were heterogeneous across metastatic lesions within individual patients. Disease phenotype at the end of life trended toward complete loss of HR expression. Nearly all (n = 7) patients exhibited extensive tumor involvement of additional organs that had not been previously diagnosed clinically and were not retrospectively visible on recent imaging. Of these seven individuals, three included organs uncommonly associated with MBC: kidney, spleen, pancreas, and ovary. Finally, we identified clinically undetectable micrometastases in several organs uncommonly involved in MBC. Our findings raise several clinically relevant questions regarding the mechanisms of metastatic progression. Insights from this study argue for better surveillance strategies for monitoring MBC. We highlight the need to capture more accurate biomarker information in the context of heterogeneous disease and urge the consideration of treatment strategies that combine multiple targeted therapies.

STING signalling compensates for low tumour mutation burden to drive anti-tumour immunity

BACKGROUND

While mutation-derived neoantigens are well recognized in generating anti-tumour T cell response, increasing evidences highlight the complex association between tumour mutation burden (TMB) and tumour infiltrating lymphocytes (TILs). The exploration of non-TMB determinants of active immune response could improve the prognosis prediction and provide guidance for current immunotherapy.

METHODS

The transcriptomic and whole exome sequence data in The Cancer Genome Atlas were used to examine the relationship between TMB and exhausted CD8+ T cells (Tex), as an indicator of tumour antigen-specific T cells across nine major cancer types. Computational clustering analysis was performed on 4510 tumours to identify different immune profiles. NanoString gene expression analysis and single cell RNA-seq analysis using fresh human breast cancer were performed for finding validation.

FINDINGS

TMB was found to be poorly correlated with active immune response in various cancer types. Patient clustering analysis revealed a group of tumours with abundant Tex but low TMB. In those tumours, we observed significantly higher expression of the stimulator of interferon genes (STING) signalling. Dendritic cells, particularly those of BATF3+ lineage, were also found to be essential for accumulation of Tex within tumours. Mechanistically, loss of genomic and cellular integrity, marked by decreased DNA damage repair, defective replication stress response, and increased apoptosis were shown to drive STING activation.

INTERPRETATION

These results highlight that TMB alone does not fully predict tumour immune profiles, with STING signalling compensating for low TMB in non-hypermutated tumours to enhance anti-tumour immunity. Translating these results, STING agonists may benefit patients with non-hypermutated tumours. STING activation may serve as an additional biomarker to predict response to immune checkpoint blockades alongside TMB. Our research also unravelled the interplay between genomic instability and STING activation, informing potential combined chemotherapy targeting the axis of genomic integrity and immunotherapy.

FUNDING

City of Hope Christopher Family Endowed Innovation Fund for Alzheimer's Disease and Breast Cancer Research in honor of Vineta Christopher; Breast Cancer Alliance Early Career Investigator Award; National Cancer Institute of the National Institutes of Health under award number R01CA256989 and R01CA240392.

PD-L1-expressing tumor-associated macrophages are immunostimulatory and associate with good clinical outcome in human breast cancer

Tumor-associated macrophages (TAMs) are the predominant cells that express programmed cell death ligand 1 (PD-L1) within human tumors in addition to cancer cells, and PD-L1+ TAMs are generally thought to be immunosuppressive within the tumor immune microenvironment (TIME). Using single-cell transcriptomic and spatial multiplex immunofluorescence analyses, we show that PD-L1+ TAMs are mature and immunostimulatory with spatial preference to T cells. In contrast, PD-L1- TAMs are immunosuppressive and spatially co-localize with cancer cells. Either higher density of PD-L1+ TAMs alone or ratio of PD-L1+/PD-L1- TAMs correlate with favorable clinical outcome in two independent cohorts of patients with breast cancer. Mechanistically, we show that PD-L1 is upregulated during the monocyte-to-macrophage maturation and differentiation process and does not require external IFN-γ stimulus. Functionally, PD-L1+ TAMs are more mature/activated and promote CD8+ T cells proliferation and cytotoxic capacity. Together, our findings reveal insights into the immunological significance of PD-L1 within the TIME.

Systems profiling reveals recurrently dysregulated cytokine signaling responses in ER+ breast cancer patients' blood

Cytokines mediate cell-to-cell communication across the immune system and therefore are critical to immunosurveillance in cancer and other diseases. Several cytokines show dysregulated abundance or signaling responses in breast cancer, associated with the disease and differences in survival and progression. Cytokines operate in a coordinated manner to affect immune surveillance and regulate one another, necessitating a systems approach for a complete picture of this dysregulation. Here, we profiled cytokine signaling responses of peripheral immune cells from breast cancer patients as compared to healthy controls in a multidimensional manner across ligands, cell populations, and responsive pathways. We find alterations in cytokine responsiveness across pathways and cell types that are best defined by integrated signatures across dimensions. Alterations in the abundance of a cytokine's cognate receptor do not explain differences in responsiveness. Rather, alterations in baseline signaling and receptor abundance suggesting immune cell reprogramming are associated with altered responses. These integrated features suggest a global reprogramming of immune cell communication in breast cancer.

Peritumoral Immune-suppressive Mechanisms Impede Intratumoral Lymphocyte Infiltration into Colorectal Cancer Liver versus Lung Metastases

Patients with microsatellite stable (MSS) colorectal cancer with liver metastases are resistant to immune checkpoint inhibitor (ICI) therapy, while about one-third of patients with colorectal cancer without liver metastases, particularly those with lung-only metastases, respond to ICI. We analyzed primary colorectal cancer tumors and major metastatic sites (liver, lung, peritoneal) using multiplex immunofluorescence and whole-slide spatial analyses to identify variations in immune contexture and regional localization within the tumor microenvironment. While levels of T and B cells within peritumoral regions were similar, their levels were significantly lower within the tumor core of liver and peritoneal metastases compared with lung metastases. In contrast, antigen-presenting cells (APC) and APC-T cell interactions were more abundant in all regions of lung metastases. We also identified an abundance of lymphoid aggregates throughout lung metastases, but these were present only within peritumoral regions of liver and peritoneal metastases. Larger lymphoid aggregates consistent with features of tertiary lymphoid structures were observed within or adjacent to primary tumors, but not metastatic lesions. Our findings were validated using NanoString GeoMx DSP, which further showed that liver metastases had higher expression of immune-suppressive markers, while lung metastases showed higher proinflammatory activity and T-cell activation markers. Peritoneal metastases demonstrated higher expression of cancer-associated fibroblast-related proteins and upregulated PD-1/PD-L1 signaling molecules. Our results demonstrate that functional status and spatial distribution of immune cells vary significantly across different metastatic sites. These findings suggest that metastatic site-dependent immune contexture may underlie discordant responses to ICI therapy in patients with MSS colorectal cancer.

SIGNIFICANCE

Our results demonstrate that functional status and spatial distribution of immune cells vary significantly across different metastatic sites in MSS colorectal cancer. These findings suggest that metastatic site-dependent immune contexture may underlie discordant responses to ICI therapy in patients with MSS colorectal cancer.

Immunogenicity and efficacy of pembrolizumab and doxorubicin in a phase I trial for patients with metastatic triple-negative breast cancer

Currently there is a limited understanding for the optimal combination of immune checkpoint inhibitor and chemotherapy for patients with metastatic triple-negative breast cancer (mTNBC). Here we evaluate the safety, efficacy, and immunogenicity of a phase I trial for patients with mTNBC treated with pembrolizumab plus doxorubicin. Patients without prior anthracycline use and 0-2 lines of prior systemic chemotherapies received pembrolizumab and doxorubicin every 3 weeks for 6 cycles followed by pembrolizumab maintenance until disease progression or intolerance. The primary objectives were safety and objective response rate per RECIST 1.1. Best responses included one complete response (CR), five partial responses (PR), two stable disease (SD), and one progression of disease (PD). Overall response rate was 67% (95% CI 13.7%, 78.8%) and clinical benefit rate at 6 months was 56% (95% CI 21.2%, 86.3%). Median PFS was 5.2 months (95% CI 4.7, NA); median OS was 15.6 months (95% CI 13.3, NA). Grade 3-4 AEs per CTCAE 4.0 were neutropenia n = 4/10 (40%), leukopenia n = 2/10 (20%), lymphopenia n = 2/10 (20%), fatigue n = 2/10 (20%), and oral mucositis n = 1/10 (10%). Immune correlates showed increased frequencies of circulating CD3 + T cells (p = 0.03) from pre-treatment to cycle 2 day 1 (C2D1). An expansion of a proliferative exhausted-like PD-1 + CD8 + T cell population was identified in 8/9 patients, and exhausted CD8 + T cells were significantly expanded from pre-treatment to C2D1 in the patient with CR (p = 0.01). In summary, anthracycline-naïve patients with mTNBC treated with the combination of pembrolizumab and doxorubicin showed an encouraging response rate and robust T cell response dynamics.Trial registration: NCT02648477.

Reprogramming of PD-1+ M2-like tumor-associated macrophages with anti-PD-L1 and lenalidomide in cutaneous T cell lymphoma

Cutaneous T cell lymphoma (CTCL) is a disfiguring and incurable disease characterized by skin-homing malignant T cells surrounded by immune cells that promote CTCL growth through an immunosuppressive tumor microenvironment (TME). Preliminary data from our phase I clinical trial of anti-programmed cell death ligand 1 (anti-PD-L1) combined with lenalidomide in patients with relapsed/refractory CTCL demonstrated promising clinical efficacy. In the current study, we analyzed the CTCL TME, which revealed a predominant PD-1+ M2-like tumor-associated macrophage (TAM) subtype with upregulated NF-κB and JAK/STAT signaling pathways and an aberrant cytokine and chemokine profile. Our in vitro studies investigated the effects of anti-PD-L1 and lenalidomide on PD-1+ M2-like TAMs. The combinatorial treatment synergistically induced functional transformation of PD-1+ M2-like TAMs toward a proinflammatory M1-like phenotype that gained phagocytic activity upon NF-κB and JAK/STAT inhibition, altered their migration through chemokine receptor alterations, and stimulated effector T cell proliferation. Lenalidomide was more effective than anti-PD-L1 in downregulation of the immunosuppressive IL-10, leading to decreased expression of both PD-1 and PD-L1. Overall, PD-1+ M2-like TAMs play an immunosuppressive role in CTCL. Anti-PD-L1 combined with lenalidomide provides a therapeutic strategy to enhance antitumor immunity by targeting PD-1+ M2-like TAMs in the CTCL TME.

Safety, tolerability, and acceptability of Lactobacillus crispatus CTV-05 (LACTIN-V) in pregnant women at high-risk of preterm birth

The vaginal microbiota is a determinant for the risk of preterm birth (PTB). Dominance of the vaginal niche by Lactobacillus crispatus associates with term delivery. This is the first observational clinical study of live vaginal biotherapeutics (Lactobacillus crispatus CTV-05 (LACTIN-V)) in pregnant women at high-risk of PTB. The primary aim was to explore safety, tolerability and acceptability of LACTIN-V in pregnancy. Women were offered a course of LACTIN-V at 14 weeks gestation for five consecutive days followed by weekly administration for six weeks. Participants were followed up at 15, 18-, 20-, 28- and 36-weeks' gestation and at delivery for assessment of adverse events, compliance and tolerability. Participants completed a questionnaire to gauge experience and acceptability. In total, 73 women were recruited, of whom eight withdrew, leaving a final cohort size of 61. Self-reported compliance to the course was high (56/60, 93%). Solicited adverse events were reported in 13 women (19%) including changes in vaginal discharge, odour, colour or consistency of urine, itching and vaginal bleeding. One unsolicited adverse event was reported as haematuria at 38 weeks gestation, but was judged to be unrelated to LACTIN-V. No serious adverse events occurred. One mild adverse event led to study withdrawal. Thirty-one women completed an experience and acceptability questionnaire. Women found LACTIN-V easy and comfortable to use and the majority (30/31, 97%) would use LACTIN-V in future pregnancies. Eight women (8/31, 26%) found the schedule of use difficult to remember. The rate of PTB <34 weeks in this cohort was 3.3% compared to 7% in a historical cohort of 2,190 women at similar background PTB risk. With satisfactory uptake and good compliance, we demonstrate that LACTIN-V is safe and accepted in pregnancy, with high tolerability. Further studies are needed to assess colonisation of Lactobacillus crispatus CTV-05 and clinical efficacy.

Bow-tie architectures in biological and artificial neural networks: Implications for network evolution and assay design

Modern artificial neural networks (ANNs) have long been designed on foundations of mathematics as opposed to their original foundations of biomimicry. However, the structure and function of these modern ANNs are often analogous to real-life biological networks. We propose that the ubiquitous information-theoretic principles underlying the development of ANNs are similar to the principles guiding the macro-evolution of biological networks and that insights gained from one field can be applied to the other. We generate hypotheses on the bow-tie network structure of the Janus kinase - signal transducers and activators of transcription (JAK-STAT) pathway, additionally informed by the evolutionary considerations, and carry out ANN simulation experiments to demonstrate that an increase in the network's input and output complexity does not necessarily require a more complex intermediate layer. This observation should guide novel biomarker discovery-namely, to prioritize sections of the biological networks in which information is most compressed as opposed to biomarkers representing the periphery of the network.

Abstract 2741: A communication theory framework for modeling cytokine-mediated signaling in healthy and breast cancer derived peripheral blood immune cells

Previous studies have shown that approximately 40% of estrogen receptor positive (ER+) breast cancer (BC) patients harbor immune signaling defects in their blood at diagnosis that predicts overall survival. The aim of this work is to apply communication theory and signal processing methods to model cytokine-mediated signaling errors in immune cells in the peripheral blood. Our approach uses communication theory concepts to develop a communication system model consisting of a transmitter, receiver, and channel, applied to the JAK/STAT signaling pathway and tested using multi-color flow cytometry analysis of peripheral blood mononuclear cells stimulated with IFNγ, IL-2, IL-6, IL-4, IL-10, IL-12, or TGFβ in samples from 2 BC patients and 4 healthy controls. We use our model to estimate the detection error rate when one of the 7 cytokines is being transduced through the JAK/STAT signaling pathway, but its signal is being received on multiple phosphorylated signal transducers and activators of transcription (pSTAT) molecules. In addition, we extend the measured error rate value to an error rate curve by varying the signal-to-noise ratio available to the receiver in our system model. Our results show a trend towards higher detection error rates in immune cells from BC patients as compared to healthy controls, which may indicate altered immune signaling and incorrect cell decisions in these patients. Also, considering different cell subtypes, our results show two orders of magnitude increase in error rate in CD4+ memory T cells compared to CD4+ naïve T cells in BC patients. With further development, we believe that our communication theory model and quantification of optimal signal detection in cells will provide a better understanding into how immune cells can accurately “decode” information to respond properly to various signals and how the immune signaling is altered in BC patients, causing better or worse outcomes. The benefit of our novel approach is that it integrates all the transmitted (cytokines) and received signals (pSTATs) into a single communications framework that can be efficiently analyzed together.

Citation Format: Adina Matache, Aleksandra Karolak, Sergio Branciamore, Andrei Rodin, Peter P. Lee, Russell C. Rockne. A communication theory framework for modeling cytokine-mediated signaling in healthy and breast cancer derived peripheral blood immune cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2741.

Abstract 5208: Circulating T cell: B cell: NK cell axis associated with response to pembrolizumab plus doxorubicin in patients with metastatic triple negative breast cancer

Introduction: The use of immune checkpoint inhibitors (ICI) in combination with chemotherapy is now standard of care for patients with programmed death ligand 1-positive (PD-L1+) metastatic triple negative breast cancer (mTNBC). However, the mechanisms of response to ICIs are still poorly understood in patients with mTNBC. Here we investigate immune correlates of response in patients with mTNBC treated with programmed cell death protein 1 (PD-1) receptor-targeting pembrolizumab and doxorubicin (n=9).

Methods: Patients received pembrolizumab and doxorubicin every 3 weeks for a total of 6 cycles followed by pembrolizumab maintenance until disease progression. Objective response rates (ORR per RECIST 1.1) were: N=1 complete response (CR), N=4 partial responses (PR), N=3 stable disease (SD), and N=1 progression of disease (PD). Baseline tumor biopsies were collected for PD-L1 (22C3 antibody) and TILs analysis, and peripheral blood was collected for immune correlatives. Circulating peripheral blood mononuclear cells (PBMCs) were assessed by high parameter flow cytometry with samples collected at timepoints cycle 1 day 1 (C1D1), cycle 2 day 1 (C2D1), and cycle 3 day 1 (C3D1)

Results: No association between response and tumor infiltrating lymphocyte (TIL) scoring or PD-L1 expression were observed. Circulating exhausted CD8+ T cells (PD-1 high CD39+) were identified at baseline in all patients, with the patient with PD having a low frequency of exhausted CD8+ T cells (0.08% in PD vs. 0.3% mean in CR/PR/SD) at baseline. In the patient with PD, the following results were observed relative to other patients: high levels of antibody-secreting B cells (ASC, 15.2% in PD vs. 1.5% mean in CR/PR/SD), CD4+ follicular helper T cells (Tfh, 8.47% PD vs. 2.6% mean in CR/PR/SD), and terminally differentiated NK cells (11.0% PD vs. 6.3% mean CR/PR/SD) at baseline. From baseline to C2D1, the patient who achieved CR demonstrated robust expansion of exhausted CD8+ T cells (4.4-fold change in CR vs. 1.4-fold change in PR/SD/PD).

Conclusion: Our data suggests that both baseline immune profile ‘setpoints’ and dynamic remodeling of immune features, including expansion of exhausted CD8+ T cells, are associated with response to ICIs in patients with mTNBC. Lack of response to ICIs is defined not only by a lack of CD8+ T cell expansion, but also by high levels of circulating ASCs, Tfh, and terminal NK cells at baseline. Additional studies to further explore and validate features of this T cell: B cell: NK cell axis and response to ICIs in patients with mTNBC are ongoing.

Citation Format: Colt A. Egelston, Weihua Guo, Peter P. Lee, Susan E. Yost, James R. Waisman, Yuan Yuan. Circulating T cell: B cell: NK cell axis associated with response to pembrolizumab plus doxorubicin in patients with metastatic triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5208.

Comprehensive immune profiling unravels evolution of spatial distribution and immune repertoire in tumor microenvironment from primary to metastatic triple-negative breast cancer

1079

Background: Immune checkpoint inhibitors (ICI) have improved PFS and OS in metastatic triple-negative breast cancer (mTNBC), but benefit is limited to PD-L1 positive tumors. Metastatic tumors are notorious for deficient immune cell infiltration and immunosuppressive features that may limit responses to ICI in mTNBC. However, the underlying mechanisms for the weak immunogenicity of the metastatic tumor immune microenvironment (TIME) and related poor ICI responses are still not well understood. The current study was designed to investigate the evolution of the TIME between paired primary and metastatic TNBCs. Methods: Spatial distribution of 37 key immune regulators using the NanoString digital spatial profiling (DSP) platform was analyzed. 452 regions of interests (ROIs) from 33 primary tumors (PT) and 29 metastatic tumors (MT) including 28 paired specimens, were selected based on CD45+ immune hotspots, and the protein expression levels of the key immune regulators were quantified within pan-cytokeratin (panCK) and CD45 masked regions, respectively. In parallel, we examined the clonality of tumor infiltrating B cell receptors by reconstructing the immune repertoire from bulk RNA-seq data. Results: Using the DSP platform, we confirmed reduced immune infiltration (e.g., CD3 and CD20) in both panCK and CD45 masked regions of MT, while CD8A and CD11c (padj = 2.8×10-7 and 2.1×10-6) expression was only observed in panCK masked regions of MT compared with PT. A significant shift in myeloid composition between PT and MT as evidenced by increased CD68 signal (padj = 5.8×10-4) in CD45 masked regions of MT was identified. Within MT, PD-L1 signal was substantially higher (padj = 0.030) in CD45 masked regions only, while PD1 counts were lower (padj = 0.035) in panCK masked regions. This suggests the limited responses to ICI for MT may stem from relatively low expression of activated and targetable T cell subsets in MT islands. In support of the lower CD20 counts in MT, immune repertoire analysis revealed B cell receptor (BCR) repertoire diversity (represented by Gini index) was substantially lower in MT than PT (p = 0.041) suggesting that the ability of B cells to recognize a wide variety of tumor antigens in MT is greatly reduced in contrast to PT. Conclusions: Through comprehensive analysis of the TIME spatial organization within paired PT and MT, a significant reduction in dendritic cell/macrophage ratios (CD11c/CD68), reduced tumor localized T cell activation (CD8, PD1, PD-L1), and reduced B cell diversity (BCR clonality) are key features of the reduced immunogenicity of the metastatic TIME in TNBC. Further work to understand key mechanistic features driving the evolution of these differences in TIME between primary and metastatic tumors are ongoing.

PD-L1 blockade restores CAR T cell activity through IFN-γ-regulation of CD163+ M2 macrophages

BACKGROUND

The immune suppressive tumor microenvironment (TME) that inhibits T cell infiltration, survival, and antitumor activity has posed a major challenge for developing effective immunotherapies for solid tumors. Chimeric antigen receptor (CAR)-engineered T cell therapy has shown unprecedented clinical response in treating patients with hematological malignancies, and intense investigation is underway to achieve similar responses with solid tumors. Immunologically cold tumors, including prostate cancers, are often infiltrated with abundant tumor-associated macrophages (TAMs), and infiltration of CD163⁺ M2 macrophages correlates with tumor progression and poor responses to immunotherapy. However, the impact of TAMs on CAR T cell activity alone and in combination with TME immunomodulators is unclear.

METHODS

To model this in vitro, we utilized a novel co-culture system with tumor cells, CAR T cells, and polarized M1 or M2 macrophages from CD14⁺ peripheral blood mononuclear cells collected from healthy human donors. Tumor cell killing, T cell activation and proliferation, and macrophage phenotypes were evaluated by flow cytometry, cytokine production, RNA sequencing, and functional blockade of signaling pathways using antibodies and small molecule inhibitors. We also evaluated the TME in humanized mice following CAR T cell therapy for validation of our in vitro findings.

RESULTS

We observed inhibition of CAR T cell activity with the presence of M2 macrophages, but not M1 macrophages, coinciding with a robust induction of programmed death ligand-1 (PD-L1) in M2 macrophages. We observed similar PD-L1 expression in TAMs following CAR T cell therapy in the TME of humanized mice. PD-L1, but not programmed cell death protein-1, blockade in combination with CAR T cell therapy altered phenotypes to more M1-like subsets and led to loss of CD163⁺ M2 macrophages via interferon-γ signaling, resulting in improved antitumor activity of CAR T cells.

CONCLUSION

This study reveals an alternative mechanism by which the combination of CAR T cells and immune checkpoint blockade modulates the immune landscape of solid tumors to enhance therapeutic efficacy of CAR T cells.

B cell receptor signaling strength modulates cancer immunity

Tumor-infiltrating B cells exert antitumor effects by producing antibodies against tumor-associated antigens. Conversely, B cells may promote tumors through the production of factors that dampen antitumor immunity. In this issue of the JCI, Bing Yang, Zhen Zhang, et al. investigated the roles of B cell receptor (BCR) signaling in antitumor immunity, focusing on the role of an Asia-specific variant of human immunoglobulin G1 (IgG1) containing a Gly396 to Arg396 substitution (hIgG1-G396R) in colorectal cancer (CRC). Epidemiological analysis revealed an association between hIgG1-G396R and progression-free survival in CRC. Human samples and mouse models of CRC showed plasma cells, as opposed to B cells, infiltrating the tumor microenvironment. Notably, patients with the hIgG1-G396R variant had increased CD8⁺ T cells, dendritic cells, and tertiary lymphoid structure density. These findings indicate that the hIgG1-G396R variant represses tumorigenesis by enhancing B cell responses, and suggest that modulating BCR signaling could improve the efficacy of immunotherapy in cancer.

Abstract P1-06-01: Insights from rapid autopsy shed light on mechanisms of cancer dissemination in metastatic breast cancer

Previously we presented our initial findings from a 9-patient rapid autopsy pilot for metastatic breast cancer (MBC). At the time of procurement, one third of subjects exhibited clinically unidentified diseased sites in organs not commonly associated with breast cancer metastases, including ovary, kidney, and pancreas. In two other instances, “resolved” bone specimens (as measured by absence of FTG uptake in PET/CT imaging) were later determined to be &gt;30% tumor positive when assessed by a pathologist. We now expand upon these findings in a more in-depth exploration of the presence of micro-metastases in presumed tumor-negative tissues. A subset of tumor-free tissues were selected from each patient (average of 10 specimens per patient). All selected specimens were negative by clinical imaging, appeared grossly normal at procurement, and were reported to be tumor negative by H&E assessment by a clinical pathologist. We included organs both commonly and uncommonly involved in MBC, including lung, bone, spleen, pancreas, kidney, and non-tumor draining lymph nodes. Tissues were stained for one or more of the markers, pan-cytokeratin, GATA-3, HMFG, MUC1, and ER (if patient was previously ER+), depending on tissue type. Of the 87 total specimens assessed, we identified micro-metastases in 13 specimens from 4 individual patients. Across these 4 patients, micro-metastases were found in lung, bone, pancreas, spleen, and several non-tumor draining lymph nodes. While lung and bone are commonly involved in MBC and these results are not entirely surprising, pancreas and spleen involvement is extraordinarily rare. Further surprising was the identification of micro-metastases in several lymph nodes that were not located anatomically downstream from a disease-involved organ. Image patterns demonstrate tumor cell infiltration into the lymph node within the subcapsular sinus. Presence of micro-metastases in tumor-negative tissue did not correlate with tumor hormone status or cancer type (e.g. lobular vs DCIS). Combined with our previous findings, we now report unexpected and clinically undiagnosed disease involvement in 6/9, or two-thirds, of our patients. Based on these findings, we hypothesize that cancer stem cells and/or micro-metastases are present throughout the body, in all tissue types, and that their ability to grow into tumors is regulated by the local immune microenvironment. Lastly, the differing roles and mechanics of lymphatic vs hematological spread in metastatic disease has long been discussed. Our findings provide strong evidence for cancer dissemination through the lymphatics system. Further study is necessary to better understand the timing of metastatic spread, whether systemic dissemination occurs early or later in disease, and if conducive metastatic or pre-metastatic niches are already present throughout the body at the time of primary diagnosis or if these permissive environments develop slowly overtime.

Citation Format: Eliza R. Bacon, Kena Ihle, Colt Egelston, Weihua Guo, Diana Simons, Dan Schmolze, Christina Wei, Lusine Tumyan, Peter P Lee, James R. Waisman. Insights from rapid autopsy shed light on mechanisms of cancer dissemination in metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-06-01.

Tumor-infiltrating exhausted CD8+ T cells dictate reduced survival in premenopausal estrogen receptor-positive breast cancer

CD8⁺ tumor-infiltrating lymphocytes (TILs) are associated with improved survival in triple-negative breast cancer (TNBC) yet have no association with survival in estrogen receptor–positive (ER⁺) BC. The basis for these contrasting findings remains elusive. We identified subsets of BC tumors infiltrated by CD8⁺ T cells with characteristic features of exhausted T cells (T_EX). Tumors with abundant CD8⁺ T_EX exhibited a distinct tumor microenvironment marked by amplified interferon-γ signaling–related pathways and higher programmed death ligand 1 expression. Paradoxically, higher levels of tumor-infiltrating CD8⁺ T_EX associated with decreased overall survival of patients with ER⁺ BC but not patients with TNBC. Moreover, high tumor expression of a CD8⁺ T_EX signature identified dramatically reduced survival in premenopausal, but not postmenopausal, patients with ER⁺ BC. Finally, we demonstrated the value of a tumor T_EX signature score in identifying high-risk premenopausal ER⁺ BC patients among those with intermediate Oncotype DX Breast Recurrence Scores. Our data highlight the complex relationship between CD8⁺ TILs, interferon-γ signaling, and ER status in BC patient survival. This work identifies tumor-infiltrating CD8⁺ T_EX as a key feature of reduced survival outcomes in premenopausal patients with early-stage ER⁺ BC.

Clinical Response to Immunotherapy Targeting Programmed Cell Death Receptor 1/Programmed Cell Death Ligand 1 in Patients With Treatment-Resistant Microsatellite Stable Colorectal Cancer With and Without Liver Metastases

IMPORTANCE

Microsatellite stable (MSS) metastatic colorectal cancer has been historically characterized as resistant to immunotherapy. Recent studies have demonstrated limited clinical activity of programmed cell death receptor 1/programmed death ligand 1 (PD-1/PD-L1) targeting in MSS metastatic colorectal cancer. The association of metastatic disease in the liver with treatment response has not been fully investigated.

OBJECTIVE

To investigate the association of liver metastases with response to PD-1/PD-L1-targeting therapy in MSS metastatic colorectal cancer.

DESIGN, SETTING, AND PARTICIPANTS

This single-center retrospective cohort study evaluated clinical responses to PD-1- or PD-L1-targeting therapy, with or without other investigational agents, in patients with MSS metastatic colorectal cancer and disease progression after standard of care therapy from January 1, 2014, to December 31, 2020.

MAIN OUTCOMES AND MEASURES

Objective response rate (ORR) and progression-free survival (PFS), measured from initiation of PD-1/PD-L1-targeting therapy.

RESULTS

Ninety-five patients with MSS metastatic colorectal cancer were identified (54 men [56.8%]; median age, 55 [interquartile range (IQR), 49-64] years). The overall ORR was 8.4% (8 of 95 patients). Eight of 41 patients without liver metastases achieved an ORR of 19.5%, and no response was observed in 54 patients with liver metastases. The disease control rate was 58.5% (24 of 41) in patients without liver metastasis and 1.9% (1 of 54) in patients with liver metastasis. Patients without liver metastases at the time of PD-1/PD-L1-targeting treatment had a superior median PFS compared with patients with liver metastases (4.0 [IQR, 2.0-7.5] vs 1.5 [IQR, 1.0-2.0] months; P < .001). In addition, median PFS was 5.5 (IQR, 2.0-11.5) months for patients without any prior or current liver involvement at the time of PD-1/PD-L1-targeting treatment initiation. Using a multivariate Cox regression model correcting for Eastern Cooperative Oncology Group status, primary tumor location, RAS and BRAF status, tumor mutation burden, and metastatic sites, liver metastases was the variable with the most significant association with faster progression after PD-1/PD-L1 treatment inhibition (hazard ratio, 7.00; 95% CI, 3.18-15.42; P < .001).

CONCLUSIONS AND RELEVANCE

Findings of this cohort study suggest that patients with MSS metastatic colorectal cancer and without liver metastases may derive clinical benefits from checkpoint inhibitors, whereas the presence of liver metastases was associated with resistance. Further prospective studies are needed to investigate PD-1/PD-L1 inhibitors in patients with MSS metastatic colorectal cancer without liver metastases.

Spatial distribution of B cells and lymphocyte clusters as a predictor of triple-negative breast cancer outcome

While tumor infiltration by CD8+ T cells is now widely accepted to predict outcomes, the clinical significance of intratumoral B cells is less clear. We hypothesized that spatial distribution rather than density of B cells within tumors may provide prognostic significance. We developed statistical techniques (fractal dimension differences and a box-counting method 'occupancy') to analyze the spatial distribution of tumor-infiltrating lymphocytes (TILs) in human triple-negative breast cancer (TNBC). Our results indicate that B cells in good outcome tumors (no recurrence within 5 years) are spatially dispersed, while B cells in poor outcome tumors (recurrence within 3 years) are more confined. While most TILs are located within the stroma, increased numbers of spatially dispersed lymphocytes within cancer cell islands are associated with a good prognosis. B cells and T cells often form lymphocyte clusters (LCs) identified via density-based clustering. LCs consist either of T cells only or heterotypic mixtures of B and T cells. Pure B cell LCs were negligible in number. Compared to tertiary lymphoid structures (TLS), LCs have fewer lymphocytes at lower densities. Both types of LCs are more abundant and more spatially dispersed in good outcomes compared to poor outcome tumors. Heterotypic LCs in good outcome tumors are smaller and more numerous compared to poor outcome. Heterotypic LCs are also closer to cancer islands in a good outcome, with LC size decreasing as they get closer to cancer cell islands. These results illuminate the significance of the spatial distribution of B cells and LCs within tumors.

Concepts and Applications of Information Theory to Immuno-Oncology

Recent successes of immune-modulating therapies for cancer have stimulated research on information flow within the immune system and, in turn, clinical applications of concepts from information theory. Through information theory, one can describe and formalize, in a mathematically rigorous fashion, the function of interconnected components of the immune system in health and disease. Specifically, using concepts including entropy, mutual information, and channel capacity, one can quantify the storage, transmission, encoding, and flow of information within and between cellular components of the immune system on multiple temporal and spatial scales. To understand, at the quantitative level, immune signaling function and dysfunction in cancer, we present a methodology-oriented review of information-theoretic treatment of biochemical signal transduction and transmission coupled with mathematical modeling.

Ivermectin converts cold tumors hot and synergizes with immune checkpoint blockade for treatment of breast cancer

We show that treatment with the FDA-approved anti-parasitic drug ivermectin induces immunogenic cancer cell death (ICD) and robust T cell infiltration into breast tumors. As an allosteric modulator of the ATP/P2X4/P2X7 axis which operates in both cancer and immune cells, ivermectin also selectively targets immunosuppressive populations including myeloid cells and Tregs, resulting in enhanced Teff/Tregs ratio. While neither agent alone showed efficacy in vivo, combination therapy with ivermectin and checkpoint inhibitor anti-PD1 antibody achieved synergy in limiting tumor growth (p = 0.03) and promoted complete responses (p < 0.01), also leading to immunity against contralateral re-challenge with demonstrated anti-tumor immune responses. Going beyond primary tumors, this combination achieved significant reduction in relapse after neoadjuvant (p = 0.03) and adjuvant treatment (p < 0.001), and potential cures in metastatic disease (p < 0.001). Statistical modeling confirmed bona fide synergistic activity in both the adjuvant (p = 0.007) and metastatic settings (p < 0.001). Ivermectin has dual immunomodulatory and ICD-inducing effects in breast cancer, converting cold tumors hot, thus represents a rational mechanistic partner with checkpoint blockade.

Dissecting Response to Cancer Immunotherapy by Applying Bayesian Network Analysis to Flow Cytometry Data

Cancer immunotherapy, specifically immune checkpoint blockade, has been found to be effective in the treatment of metastatic cancers. However, only a subset of patients achieve clinical responses. Elucidating pretreatment biomarkers predictive of sustained clinical response is a major research priority. Another research priority is evaluating changes in the immune system before and after treatment in responders vs. nonresponders. Our group has been studying immune networks as an accurate reflection of the global immune state. Flow cytometry (FACS, fluorescence-activated cell sorting) data characterizing immune cell panels in peripheral blood mononuclear cells (PBMC) from gastroesophageal adenocarcinoma (GEA) patients were used to analyze changes in immune networks in this setting. Here, we describe a novel computational pipeline to perform secondary analyses of FACS data using systems biology/machine learning techniques and concepts. The pipeline is centered around comparative Bayesian network analyses of immune networks and is capable of detecting strong signals that conventional methods (such as FlowJo manual gating) might miss. Future studies are planned to validate and follow up the immune biomarkers (and combinations/interactions thereof) associated with clinical responses identified with this computational pipeline.

Abstract PS19-16: Utility of rapid autopsy in cancer research: Unexpected findings and lessons learned from warm autopsies of metastatic breast cancer patients

Metastatic disease is understudied largely because of inaccessibility to quality specimens for research use. The Legacy Project, a rapid or “warm”, autopsy program at City of Hope, seeks to overcome this challenge by collecting tissue from metastatic patients immediately (within 6 hours) after their death. This paradigm serves as a specimen resource to address many clinically relevant questions, such as disease heterogeneity and mechanisms driving disease progression. Using this model, we uncovered clinically relevant disease information that is normally unavailable while a subject is alive. In this study, 9 metastatic breast cancer patients and their families were approached and consented prior to death. The cohort includes a diversity of clinical presentations in terms of disease subtype, progression history, organ involvement, and final cause of death. A total of 533 specimens were collected across 9 subjects. The average time from death to specimen acquisition was 6.1 hours (range: 4.03 - 7.66 hours; median: 5.71 hours). Total number of specimens collected from each participant ranged from 38-75, with an average of 60 across all patients; the mean number of tumor-positive specimens collected was 29 (range 12-46); the mean number of non-cancer specimens collected was 31 (range 25-45). In patients with primary estrogen receptor (ER) positive disease, we observed variable heterogeneity in estrogen, progesterone, and ki67 status across metastatic lesions. Furthermore, we observed a profound shift in disease phenotype towards end of life, trending towards complete loss of hormone receptor expression and stark increase of Ki67 levels. At the time of procurement, one third of subjects exhibited clinically unidentified diseased sites in organs not commonly associated with breast cancer metastases a, including ovary, kidney, and pancreas. In two other instances, “resolved” bone specimens (as measured by absence of FTG uptake in PET/CT imaging) were later determined to be &gt;30% tumor positive when assessed by H&E. While these preliminary findings generate more questions than answers regarding mechanisms of metastatic progression and resistance to therapy, they highlight the utility of rapid autopsy in a research setting. We suggest that many unanswered clinical questions can be addressed through interrogation of post-mortem tissues and we urge research institutions to thoughtfully consider adoption of the “rapid autopsy” model.

Citation Format: Eliza R Bacon, Kena Ihle, Colt Egelston, Weihua Guo, Diana Simons, Peter P Lee, James Waisman. Utility of rapid autopsy in cancer research: Unexpected findings and lessons learned from warm autopsies of metastatic breast cancer patients [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 PS19-16.

Warburg Effect Is a Cancer Immune Evasion Mechanism Against Macrophage Immunosurveillance

Evasion of immunosurveillance is critical for cancer initiation and development. The expression of “don’t eat me” signals protects cancer cells from being phagocytosed by macrophages, and the blockade of such signals demonstrates therapeutic potential by restoring the susceptibility of cancer cells to macrophage-mediated phagocytosis. However, whether additional self-protective mechanisms play a role against macrophage surveillance remains unexplored. Here, we derived a macrophage-resistant cancer model from cells deficient in the expression of CD47, a major “don’t eat me” signal, via a macrophage selection assay. Comparative studies performed between the parental and resistant cells identified self-protective traits independent of CD47, which were examined with both pharmacological or genetic approaches in in vitro phagocytosis assays and in vivo tumor models for their roles in protecting against macrophage surveillance. Here we demonstrated that extracellular acidification resulting from glycolysis in cancer cells protected them against macrophage-mediated phagocytosis. The acidic tumor microenvironment resulted in direct inhibition of macrophage phagocytic ability and recruitment of weakly phagocytic macrophages. Targeting V-ATPase which transports excessive protons in cancer cells to acidify extracellular medium elicited a pro-phagocytic microenvironment with an increased ratio of M1-/M2-like macrophage populations, therefore inhibiting tumor development and metastasis. In addition, blockade of extracellular acidification enhanced cell surface exposure of CD71, targeting which by antibodies promoted cancer cell phagocytosis. Our results reveal that extracellular acidification due to the Warburg effect confers immune evasion ability on cancer cells. This previously unrecognized role highlights the components mediating the Warburg effect as potential targets for new immunotherapy harnessing the tumoricidal capabilities of macrophages.

A minimal model of T cell avidity may identify subtherapeutic vaccine schedules

T cells protect the body from cancer by recognising tumour-associated antigens. Recognising these antigens depends on multiple factors, one of which is T cell avidity, i.e., the total interaction strength between a T cell and a cancer cell. While both high- and low-avidity T cells can kill cancer cells, durable anti-cancer immune responses require the selection of high-avidity T cells. Previous experimentation with anti-cancer vaccines, however, has shown that most vaccines elicit low-avidity T cells. Optimising vaccine schedules may remedy this by preferentially selecting high-avidity T cells. Here, we use mathematical modelling to develop a simple, phenomenological model of avidity selection that may identify vaccine schedules that disproportionately favour low-avidity T cells. We calibrate our model to our prior, more complex model, and then validate it against several experimental data sets. We find that the sensitivity of the model's parameters change with vaccine dosage, which allows us to use a patient's data and clinical history to screen for suitable vaccine strategies.

Physics approaches to the spatial distribution of immune cells in tumors

The goal of immunotherapy is to mobilize the immune system to kill cancer cells. Immunotherapy is more effective and, in general, the prognosis is better, when more immune cells infiltrate the tumor. We explore the question of whether the spatial distribution rather than just the density of immune cells in the tumor is important in forecasting whether cancer recurs. After reviewing previous work on this issue, we introduce a novel application of maximum entropy to quantify the spatial distribution of discrete point-like objects. We apply our approach to B and T cells in images of tumor tissue taken from triple negative breast cancer patients. We find that the immune cells are more spatially dispersed in good clinical outcome (no recurrence of cancer within at least 5 years of diagnosis) compared to poor clinical outcome (recurrence within 3 years of diagnosis). Our results highlight the importance of spatial distribution of immune cells within tumors with regard to clinical outcome, and raise new questions on their role in cancer recurrence.

Connecting the Dots: Translating the Vaginal Microbiome Into a Drug

A Lactobacillus-dominated vaginal microbiota (VMB) has been associated with health and considered an important host defense mechanism against urogenital infections. Conversely, depletion of lactobacilli and increased microbial diversity, amplifies the risk of adverse gynecologic and obstetric outcomes. A common clinical condition that exemplifies dysbiosis is bacterial vaginosis (BV). BV is currently treated with antibiotics, but frequently recurs, due in part to persistent dysbiosis and failure of lactobacilli to repopulate the vagina. New treatment options are needed to address BV. The VMB is relatively simple and optimally dominated by one or several species of Lactobacillus. Lactobacillus crispatus is strongly associated with vaginal health and depleted in dysbiosis. Replenishing the dysbiotic VMB with protective L. crispatus CTV-05 is a promising approach to prevent recurrent infections and improve women's health. Here we discuss confirmation of this approach with the microbiome-based biologic drug, LACTIN-V (L. crispatus CTV-05), focusing on prevention of BV recurrence.

A Phase II Clinical Trial of Pembrolizumab and Enobosarm in Patients with Androgen Receptor-Positive Metastatic Triple-Negative Breast Cancer

LESSONS LEARNED

The combination of enobosarm and pembrolizumab was well tolerated and showed a modest clinical benefit rate of 25% at 16 weeks. Future trials investigating androgen receptor-targeted therapy in combination with immune checkpoint inhibitors are warranted.

BACKGROUND

Luminal androgen receptor is a distinct molecular subtype of triple-negative breast cancer (TNBC) defined by overexpression of androgen receptor (AR). AR-targeted therapy has shown modest activity in AR-positive (AR+) TNBC. Enobosarm (GTx-024) is a nonsteroidal selective androgen receptor modulator (SARM) that demonstrates preclinical and clinical activity in AR+ breast cancer. The current study was designed to explore the safety and efficacy of the combination of enobosarm and pembrolizumab in patients with AR+ metastatic TNBC (mTNBC).

METHODS

This study was an open-label phase II study for AR+ (≥10%, 1+ by immunohistochemistry [IHC]) mTNBC. Eligible patients received pembrolizumab 200 mg intravenous (IV) every 3 weeks and enobosarm 18 mg oral daily. The primary objective was to evaluate the safety of enobosarm plus pembrolizumab and determine the response rate. Peripheral blood, tumor biopsies, and stool samples were collected for correlative analysis.

RESULTS

The trial was stopped early because of the withdrawal of GTx-024 drug supply. Eighteen patients were enrolled, and 16 were evaluable for responses. Median age was 64 (range 36-81) years. The combination was well tolerated, with only a few grade 3 adverse events: one dry skin, one diarrhea, and one musculoskeletal ache. The responses were 1 of 16 (6%) complete response (CR), 1 of 16 (6%) partial response (PR), 2 of 16 (13%) stable disease (SD), and 12 of 16 (75%) progressive disease (PD). Response rate (RR) was 2 of 16 (13%). Clinical benefit rate (CBR) at 16 weeks was 4 of 16 (25%). Median follow-up was 24.9 months (95% confidence interval [CI], 17.5-30.9). Progression-free survival (PFS) was 2.6 months (95% CI, 1.9-3.1) and overall survival (OS) was 25.5 months (95% CI, 10.4-not reached [NR]).

CONCLUSION

The combination of enobosarm and pembrolizumab was well tolerated, with a modest clinical benefit rate of 25% at 16 weeks in heavily pretreated AR+ TNBC without preselected programmed death ligand-1 (PD-L1). Future clinical trials combining AR-targeted therapy with immune checkpoint inhibitor (ICI) for AR+ TNBC warrant investigation.

Abstract PO-080: Predicting relapse in patients with triple negative breast cancer (TNBC) using a deep-learning approach

The abundance and/or precise location of tumor infiltrating lymphocytes (TILs), especially CD8+ T cells, can serve as a prognostic indicator in various types of solid tumors. However, it is often difficult to select an appropriate algorithm in order to stratify patients into well-defined risk groups. More importantly, patient stratification results often depends on the selection of tumor regions, where subjective judgement could affect the final results. On the other hand, machine-learning approaches can help to stratify patients in an objective and automatic fashion. Based on immunofluorescence (IF) images of CD8+ T lymphocytes and cancer cells, we develop a machine-learning approach which can predict the risk of relapse for patients with Triple Negative Breast Cancer (TNBC). Tumor-section images from 9 patients with poor outcome and 15 patients with good outcome were used as a training set. Tumor-section images of 29 patients in an independent cohort were used to test the predictive power of our algorithm. One of the key innovations is dissecting the section images into patches in a size of 640 µm x 640 µm for training and test, which allows one to make use of the information in the section images despite the small number of patients. In the test cohort, 6 (out of 29) patients who belong to the poor-outcome group were all correctly identified by our algorithm; for the 23 (out of 29) patients who belong to the good-outcome group, 17 were correctly predicted with some evidence that improvement is possible if other measures, such as the grade of tumors, are factored in. Our approach does not involve arbitrarily defined metrics and can be applied to other types of cancer in which the abundance/location of CD8+ T lymphocytes/other types of cells is an indicator of prognosis. Furthermore, we showed that using limited parts of the tumor section image for predictions would give rise to inaccurate results, which suggests that tumor heterogeneity should be carefully taken into account for a rigorous evaluation of the outcome. In summary, despite the limited number of patients, we demonstrated that the deep-learning approach can make good use information in the infiltration pattern of CD8+ T lymphocytes and thereby enable prognosis. Additional data collection efforts should be made to eventually enable a more rigorous analysis.

Citation Format: Guangyuan Yu, Xuefei Li, Ting-Fang He, Tina Gruosso, Dongmei Zuo, Margarita Souleimanova, Valentina Muñoz Ramos, Atilla Omeroglu, Sarkis Meterissian, Marie-Christine Guiot, Li Yang, Yuan Yuan, Morag Park, Peter P. Lee, Herbert Levine. Predicting relapse in patients with triple negative breast cancer (TNBC) using a deep-learning approach [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-080.

Mature Dendritic Cells May Promote High-Avidity Tuning of Vaccine T Cell Responses

Therapeutic vaccines can elicit tumor-specific cytotoxic T lymphocytes (CTLs), but durable reductions in tumor burden require vaccines that stimulate high-avidity CTLs. Recent advances in immunotherapy responses have led to renewed interest in vaccine approaches, including dendritic cell vaccine strategies. However, dendritic cell requirements for vaccines that generate potent anti-tumor T-cell responses are unclear. Here we use mathematical modeling to show that, counterintuitively, increasing levels of immature dendritic cells may lead to selective expansion of high-avidity CTLs. This finding is in contrast with traditional dendritic cell vaccine approaches that have sought to harness ex vivo generated mature dendritic cells. We show that the injection of vaccine antigens in the context of increased numbers of immature dendritic cells results in a decreased overall peptide:MHC complex load that favors high-avidity CTL activation and expansion. Overall, our results provide a firm basis for further development of this approach, both alone and in combination with other immunotherapies such as checkpoint blockade.

Predicting Relapse in Patients With Triple Negative Breast Cancer (TNBC) Using a Deep-Learning Approach

The abundance and/or location of tumor infiltrating lymphocytes (TILs), especially CD8⁺ T cells, in solid tumors can serve as a prognostic indicator in various types of cancer. However, it is often difficult to select an appropriate threshold value in order to stratify patients into well-defined risk groups. It is also important to select appropriate tumor regions to quantify the abundance of TILs. On the other hand, machine-learning approaches can stratify patients in an unbiased and automatic fashion. Based on immunofluorescence (IF) images of CD8⁺ T lymphocytes and cancer cells, we develop a machine-learning approach which can predict the risk of relapse for patients with Triple Negative Breast Cancer (TNBC). Tumor-section images from 9 patients with poor outcome and 15 patients with good outcome were used as a training set. Tumor-section images of 29 patients in an independent cohort were used to test the predictive power of our algorithm. In the test cohort, 6 (out of 29) patients who belong to the poor-outcome group were all correctly identified by our algorithm; for the 23 (out of 29) patients who belong to the good-outcome group, 17 were correctly predicted with some evidence that improvement is possible if other measures, such as the grade of tumors, are factored in. Our approach does not involve arbitrarily defined metrics and can be applied to other types of cancer in which the abundance/location of CD8⁺ T lymphocytes/other types of cells is an indicator of prognosis.

Abstract 1689: Intranodal self-correlation analysis reveals differences in gene-to-gene interactions between lymph nodes draining cold vs. hot triple-negative breast tumors

Hot tumors (i.e., tumors with more infiltrating lymphocytes) are generally associated with better prognosis and response to immune checkpoint blockade therapies in TNBC. Higher tumor mutation burden (TMB) has been associated with hot tumors and considered a potential reason why hot tumors may have more tumor infiltrating lymphocytes (TILs) compared to cold tumors. However, TMB does not fully explain immune infiltration. We hypothesized that tumor draining lymph nodes (TDLNs) play an important role in lymphocyte infiltration into tumors. To study the functional features of LNs draining cold vs. hot tumors, we characterized the expression of 730 immune functional genes of 15 tumor-free TDLNs from paired cold (n = 7) and hot (n = 8) tumors based on low (&lt;10%) or high (&gt;60%) TIL percentages defined by pathologists in H&E stained slides. By standard differential gene expression (DGE) analysis, there were similar transcriptomic profiles in TDLNs between cold and hot cohorts. Since DGE analysis only provides comparison of average gene expression, it cannot compare gene-to-gene interactions. Therefore, to further investigate differences in intranodal gene-to-gene interactions, we implemented self-correlation analysis (i.e., generating clustered gene-to-gene correlations) to both cohorts. Results showed that TDLNs generally present weaker intranodal regulations (i.e., less significantly correlated gene pairs and smaller organized clusters) in the cold cohort. By further comparing specific gene-to-gene correlations, the GATA3-CXCR1 correlation in the cold cohort were found to be negative (rCold = -0.56), while positive (rHot = 0.90) in the hot cohort. Similar opposite correlations were also found in TBX21-CXCR1 pair (rCold = 0.85, rHot = -0.88). Since CXCR1 would be downregulated during the maturation of dendritic cells (DCs) and T cell differentiation, these results suggest that matured dendritic cells within TDLNs from cold tumors may preferably prime naïve CD4+ T cells to T helper 2 (Th2) cells. In contrast, TDLNs from hot tumors have an opposite preference to T helper 1 (Th1) cells. In addition, a positive CD4-STAT6 correlation (r = 0.88, p-value = 0.0084) was also observed, which further indicated a preference to Th2 cells in TDLNs from cold tumors. In summary, by applying intranodal self-correlation analysis to TDLNs from cold and hot tumors, opposite preferences of CD4+ naïve T cell differentiation in TDLNs are suggested. The weaker regulation and preference of Th2 cells in TDLNs from cold tumors may hinder lymphocyte infiltration into the tumor.

Citation Format: Weihua Guo, Minhui Lim, Jiayi Tan, Lei Wang, Ting-fang He, Shawn Solomon, Colt A. Egelston, Diana L. Simons, Daniel Schmolze, James Waisman, Peter P. Lee. Intranodal self-correlation analysis reveals differences in gene-to-gene interactions between lymph nodes draining cold vs. hot triple-negative breast tumors [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 1689.

Association of molecular characteristics with survival in advanced non-small cell lung cancer patients treated with checkpoint inhibitors

OBJECTIVES

Immune checkpoint inhibitors (ICIs) have changed the landscape of lung cancer therapy. However significant proportions of patients have primary or acquired resistance to ICIs. Molecular characterization is critical for patient selection and overcoming resistance to checkpoint inhibitors. The purpose of this study is to investigate the molecular characteristics associated with ICIs outcomes in advanced non-small cell lung cancer (NSCLC) patients.

MATERIALS AND METHODS

All advanced stage NSCLC patients at City of Hope who received ICIs (pembrolizumab, nivolumab, atezolizumab, and durvalumab) were identified retrospectively. Overall survival (OS, from the start of the ICIs), Pathology and information on genomic alterations (GAs) including next-generation sequencing (NGS) data, tumor mutation burden (TMB), and Programmed death-ligand 1 (PD-L1) levels were collected. Chi-square and Fisher's exact test, Log-rank test were used for comparison of demographics, and survival curves respectively. Univariate and multivariate COX proportional hazards model was used for survival analysis.

RESULTS

346 NSCLC patients were identified. Univariate and multivariate analysis found the association of OS with PD-L1 level ≥50% (Hazard ratio [HR], 0.19; 95% confidence interval [CI], 0.06-0.59; P < 0.01), EGFR (HR 7.38; 95% CI, 1.15-47.42; P < 0.05), and TET2 (HR 0.15; 95% CI, 0.03-0.90; P < 0.05). The median OS was not reached [NR] for the 12 patients who had genomic alterations (GAs) in TET2 (12/108, 11%) versus (vs) 11.5 months in TET2 negative patients (98/108, 89%). Interestingly, GAs in TET2 and FANCA were mutually exclusive and patients who had GAs in FANCA gene (6%) had shorter OS (5.5 months vs 14.5 months, Log-rank test, P < 0.05).

CONCLUSIONS

We described the clinical and molecular features of NSCLC patients treated with ICIs. The association of GAs in TET2 with longer OS and its mutual exclusivity with FANCA GAs were insightful for developing novel therapeutic strategies to improve ICIs outcomes in NSCLC.

Arhgap25 Deficiency Leads to Decreased Numbers of Peripheral Blood B Cells and Defective Germinal Center Reactions

Rho family GTPases are critical for normal B cell development and function, and their activity is regulated by a large and complex network of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). However, the role of GAPs in B cell development is poorly understood. In this study, we show that the novel Rac-GAP ARHGAP25 is important for B cell development in mice in a CXCR4-dependent manner. We show that Arhgap25 deficiency in mice leads to a significant decrease in peripheral blood B cell numbers as well as defects in mature B cell differentiation. Arhgap25^-/- B cells respond to Ag stimulation in vitro and in vivo but have impaired germinal center formation and decreased IgG1 class switching. Additionally, Arhgap25^-/- B cells show evidence of increased baseline motility and augmented chemotaxis to CXCL12. Taken together, these studies demonstrate an important role for Arhgap25 in peripheral B cell development and Ag response.

Organ specificity dictates tumor immune infiltration and composition in metastatic breast cancer; lessons from a rapid autopsy tissue collection study

1032

Background: Immune composition in the tumor microenvironment (TME) of patient tumors has proven to play a central role in the propensity of tumors to metastasize and respond to therapy. Evidence has suggested that the metastatic TME is immune aberrant, however limited sample size and numbers has made assessment of the immune TME in the development of multi-organ metastases difficult. Here we utilize a rapid autopsy tissue collection protocol to assess the infiltration and composition of the immune TME in numerous metastatic tissue sites, paired disease-free tissue sites, and the associated tissue draining lymph nodes. Methods: Post-mortem tissues were collected from six metastatic breast cancer patients shortly after death through City of Hope’s “Legacy Project for Rapid Tissue Donation” Program. The average post mortem interval (PMI) for tissue collection was 6 hours. Collected specimens include metastatic lesions and paired non-cancer samples from every cancer-involved organ, disease-free specimens from non-involved major organs, distant and tumor-draining lymph nodes (both cancer-infiltrated and disease free), as well as blood. Immediately following collection, specimens were processed into single cell suspension for flow cytometry. Over 80 immune cell phenotypes were assessed, including CD8+ and CD4+ T cell subsets, B cell subsets, natural killer (NK) cells, tumor associated macrophages (TAMs), dendritic cell subsets, and other cells. Results: Tumor infiltrated tissues were found to have comparable immune cell densities and composition compared to paired disease-free tissues of the same organ type. However, immune cell densities in metastatic tissues and disease-free tissues were significantly different between organ types, with lung immune infiltration consistently being greater than liver tissues. Differences in immune composition between tissue sites were also observed. Notably, liver tissues favored the presence of central memory CD8+ T cells, while lung tissues favored the presence of CD8+ tissue resident memory T cells. Relative to disease-free lung tissues, tumor infiltrated lungs contained diminished frequencies of CD8+ tissue resident memory T cells and altered B cell phenotypes. Conclusions: These data suggest that immune monitoring and trafficking of metastatic tissues site is dictated by organ type, which can be altered in composition by tumor infiltration. Further studies such as these may reveal organ-specific mechanisms of response to therapeutic interventions.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

A dynamical model of oncotripsy by mechanical cell fatigue: selective cancer cell ablation by low-intensity pulsed ultrasound

The method of oncotripsy, first proposed in Heyden & Ortiz (Heyden & Ortiz 2016 J. Mech. Phys. Solids 92, 164-175 (doi:10.1016/j.jmps.2016.04.016)), exploits aberrations in the material properties and morphology of cancerous cells in order to ablate them selectively by means of tuned low-intensity pulsed ultrasound. We propose the dynamical model of oncotripsy that follows as an application of cell dynamics, statistical mechanical theory of network elasticity and 'birth-death' kinetics to describe the processes of damage and repair of the cytoskeleton. We also develop a reduced dynamical model that approximates the three-dimensional dynamics of the cell and facilitates parametric studies, including sensitivity analysis and process optimization. We show that the dynamical model predicts-and provides a conceptual basis for understanding-the oncotripsy effect and other trends in the data of Mittelstein et al. (Mittelstein et al. 2019 Appl. Phys. Lett. 116, 013701 (doi:10.1063/1.5128627)), for cells in suspension, including the dependence of cell-death curves on cell and process parameters.

Breast cancer induces systemic immune changes on cytokine signaling in peripheral blood monocytes and lymphocytes

Background

It is increasingly recognized that cancer progression induces systemic immune changes in the host. Alterations in number and function of immune cells have been identified in cancer patients’ peripheral blood and lymphoid organs. Recently, we found dysregulated cytokine signaling in peripheral blood T cells from breast cancer (BC) patients, even those with localized disease.

Methods

We used phosphoflow cytometry to determine the clinical significance of cytokine signaling responsiveness in peripheral blood monocytes from non-metastatic BC patients at diagnosis. We also examined the correlation between cytokine signaling in peripheral monocytes and the number of tumor-infiltrating macrophages in paired breast tumors.

Findings

Our results show that cytokine (IFNγ) signaling may also be dysregulated in peripheral blood monocytes at diagnosis, specifically in BC patients who later relapsed. Some patients exhibited concurrent cytokine signaling defects in monocytes and lymphocytes at diagnosis, which predict the risk of future relapse in two independent cohorts of BC patients. Moreover, IFNγ signaling negatively correlates with expression of CSF1R on monocytes, thus modulating their ability to infiltrate into tumors.

Interpretation

Our results demonstrate that tumor-induced systemic immune changes are evident in peripheral blood immune cells for both myeloid and lymphoid lineages, and point to cytokine signaling responsiveness as important biomarkers to evaluate the overall immune status of BC patients.

Funding

This study was supported by the Department of Defense Breast Cancer Research Program (BCRP), The V Foundation, Stand Up to Cancer (SU2C), and Breast Cancer Research Foundation (BCRF).

STAT3 Activation-Induced Fatty Acid Oxidation in CD8+ T Effector Cells Is Critical for Obesity-Promoted Breast Tumor Growth

Although obesity is known to be critical for cancer development, how obesity negatively impacts antitumor immune responses remains largely unknown. Here, we show that increased fatty acid oxidation (FAO) driven by activated STAT3 in CD8+ T effector cells is critical for obesity-associated breast tumor progression. Ablating T cell Stat3 or treatment with an FAO inhibitor in obese mice spontaneously developing breast tumor reduces FAO, increases glycolysis and CD8+ T effector cell functions, leading to inhibition of breast tumor development. Moreover, PD-1 ligation in CD8+ T cells activates STAT3 to increase FAO, inhibiting CD8+ T effector cell glycolysis and functions. Finally, leptin enriched in mammary adipocytes and fat tissues downregulates CD8+ T cell effector functions through activating STAT3-FAO and inhibiting glycolysis. We identify a critical role of increased oxidation of fatty acids driven by leptin and PD-1 through STAT3 in inhibiting CD8+ T effector cell glycolysis and in promoting obesity-associated breast tumorigenesis.

A Pilot Feasibility Study of Yttrium-90 Liver Radioembolization Followed by Durvalumab and Tremelimumab in Patients with Microsatellite Stable Colorectal Cancer Liver Metastases

LESSONS LEARNED

Radioembolization with yttrium-90 resin microspheres can be combined safely with full doses of durvalumab and tremelimumab in patients with metastatic colorectal cancer. Regional radioembolization with yttrium-90 resin microspheres did not result in any hepatic or extrahepatic responses to a combination of durvalumab and tremelimumab. The lack of immunomodulatory responses to yttrium-90 on biopsies before and after treatment rules out a potential role for this strategy in converting a "cold tumor" into an "inflamed," immune responsive tumor.

BACKGROUND

PD-1 inhibitors have been ineffective in microsatellite stable (MSS) metastatic colorectal cancer (CRC). Preclinical models suggest that radiation therapy may sensitize MSS CRC to PD-1 blockade.

METHODS

Patients with MSS metastatic CRC with liver-predominant disease who progressed following at least one prior line of treatment were treated with yttrium-90 (Y90) radioembolization to the liver (SIR-Spheres; Sirtex, Woburn, MA) followed 2-3 weeks later by the combination of durvalumab and tremelimumab. A Simon two-stage design was implemented, with a planned expansion to 18 patients if at least one response was noted in the first nine patients.

RESULTS

Nine patients enrolled in the first stage of the study, all with progressive disease (PD) during or after their first two cycles of treatment. Per preplanned design, the study was closed because of futility. No treatment-related grade 3 or greater toxicities were recorded. Correlative studies with tumor biopsies showed low levels of tumor-infiltrating lymphocyte (TIL) infiltration in tumor cancer islands before and after Y90 radioembolization.

CONCLUSION

Y90 radioembolization can be added safely to durvalumab and tremelimumab but did not promote tumor-directed immune responses against liver-metastasized MSS CRC.

Resident memory CD8+ T cells within cancer islands mediate survival in breast cancer patients

CD8+ tumor-infiltrating lymphocytes (TILs) correlate with relapse-free survival (RFS) in most cancer types, including breast cancer. However, subset composition, functional status, and spatial location of CD8+ TILs in relation to RFS in human breast tumors remain unclear. Spatial tissue analysis via quantitative immunofluorescence showed that infiltration of CD8+ T cells into cancer islands was more significantly associated with RFS than CD8+ T cell infiltration into either tumor stroma or total tumor. Localization into cancer islands within tumors is mediated by expression of the integrin CD103, which is a marker for tissue-resident memory T cells (TRMs). Analysis of fresh tumor samples revealed that CD8+ TRMs are functionally similar to other CD8+ TILs, suggesting that the basis of their protective effect is their spatial distribution rather than functional differences. Indeed, CD103+ TRMs, as compared with CD103-CD8+ TILs, are enriched within cancer islands, and CD8+ TRM proximity to cancer cells drives the association of CD8+ TIL densities with RFS. Together, these findings reveal the importance of cancer island-localized CD8+ TRMs in surveillance of the breast tumor microenvironment and as a critical determinant of RFS in patients with breast cancer.

Immune overdrive signature in colorectal tumor subset predicts poor clinical outcome

The prognostic value of immune cell infiltration within the tumor microenvironment (TME) has been extensively investigated via histological and genomic approaches. Based on the positive prognostic value of T cell infiltration, Immunoscore has been developed and validated for predicting risk of recurrence for colorectal cancer (CRC). Also, association between a consensus T helper 1 (Th-1) immune response and favorable clinical outcomes has been observed across multiple cancer types. Here, we reanalyzed public genomic data sets from The Cancer Genome Atlas (TCGA) and NCBI Gene Expression Omnibus (NCBI-GEO) and performed multispectral immunohistochemistry (IHC) on a cohort of colorectal tumors. We identified and characterized a risk group, representing approximately 10% of CRC patients, with high intratumoral CD8+ T cell infiltration, but poor prognosis. These tumors included both microsatellite instable (MSI) and stable (MSS) phenotypes and had a high density of tumor-associated macrophages (TAMs) that expressed CD274 (programmed death-ligand 1 [PD-L1]), TGF-β activation, and an immune overdrive signature characterized by the overexpression of immune response and checkpoint genes. Our findings illustrate that CRC patients may have poor prognosis despite high CD8+ T cell infiltration and provide CD274 as a simple biomarker for identifying these patients.

Connecting blood and intratumoral Treg cell activity in predicting future relapse in breast cancer

Regulatory T (T_reg) cells play a major role in the development of an immunosuppressive tumor microenvironment. The origin of intratumoral T_reg cells and their relationship with peripheral blood T_reg cells remain unclear. T_reg cells consist of at least three functionally distinct subpopulations. Here we show that peripheral blood CD45RA^-FOXP3^hi T_reg cells (T_reg II cells) are phenotypically closest to intratumoral T_reg cells, including in their expression of CCR8. Analyses of T cell antigen receptor repertoires further support the hypothesis that intratumoral T_reg cells may originate primarily from peripheral blood T_reg II cells. Moreover, the signaling responsiveness of peripheral blood T_reg II cells to immunosuppressive, T helper type 1 (T_H1) and T helper type 2 (T_H2) cytokines reflects intratumoral immunosuppressive potential, and predicts future relapse in two independent cohorts of patients with breast cancer. Together, our findings give important insights into the relationship between peripheral blood T_reg cells and intratumoral T_reg cells, and highlight cytokine signaling responsiveness as a key determinant of intratumoral immunosuppressive potential and clinical outcome.

Abstract 528: Radioembolization followed by durvalumab and tremelimumab does not induce immune responses against liver-metastasized MSS colorectal cancer

Introduction: PD-1 inhibitors have been ineffective in microsatellite stable (MSS) metastatic colorectal cancer (mCRC). Preclinical models suggest that radiation therapy may sensitize MSS CRC to PD-1 blockade. This constitutes the rationale for combining radioembolization to the liver in patients (pts) with MSS CRC with liver metastasis.

Methods: Pts with MSS mCRC with liver predominant disease who progressed following at least 1 prior line of treatment, were eligible for study treatment. Treatment consisted of Y90 radioembolization to the liver (SIRTEX®) followed 2-3 weeks later by the intravenous (IV) combination of durvalumab (D) at 1500 mg and tremelimumab (T) at 75 mg Q4W for 4 months, followed by D 1500 mg Q4W x 8 cycles, or until disease progression (PD). Tumor biopsies were obtained at baseline, 1-2 weeks post SIR-Spheres®, and 2-3 weeks after D+T. A Simon 2-stage design was implemented, with a planned expansion to 18 patients if at least 1 response is noted in the 1st 9 pts. Correlative studies included tumor and peripheral blood flow cytometry, serum cytokine assays, and tumor IHC multiplex assay for CD8, CD4, CD68 and Cytokeratin20 expression. Immune and cancer related gene expression of the tumor microenvironment was analyzed via NanoString.

Results: 9 pts enrolled in the 1st stage of the study, all with PD within or after their first 2 cycles of treatment. Per pre-planned design, the study was closed for futility. Here we report our correlative study for this trial. Based on IHC, intratumoral TILs (CD4 and CD8 T cells) were not detectable on any of the serial tumor biopsies (pre-Y90, post-Y90, and post D+T), while heavy CD68+ macrophage infiltration was consistently observed. Such observations were statistically validated by comparing paired serial samples using NanoString. Increased expression of collagen genes, such as COL1A1, COL1A2, and COL3A1, following Y90 was noted, as reported in literatures for cases with chemo and radiation resistance. MDM2, known to associate with resistance to PD-1/PD-L1 inhibitors, was also upregulated following Y90. Furthermore, flow cytometry results showed no difference in CD4+ T cells, CD8+T cells, CD20+B cells, CD33+HLA-DR-MDSCs, and CD4+Foxp3+ regulatory T cells based on paired serial PBMC samples. However, we observed a significant increase in PD-1+CD4+ and PD-1+CD8+ T cell subpopulations in PBMC following D+T, which agrees with other reports that PD-1/PD-L1 targeting leads to the expansion of PD-1+ T cells. In addition, CD3-CD56+ NK cell population was increased following D+T when compared with Y90.

Conclusion: Y90 radioembolization can be added safely to D+T but did not promote tumor-directed immune responses against liver-metastasized MSS CRC. The associated correlative studies do not support a role for Y90 radioembolization to convert immunologically ‘cold’ tumors into ‘hot’ tumors.

Citation Format: Chongkai Wang, John Park, Ching Ouyang, Raju Pillai, Jeffrey Longmate, Holly Yin, Christian Avalos, Maricel Gozo, Colt Egelston, Peter P. Lee, Marwan G. Fakih. Radioembolization followed by durvalumab and tremelimumab does not induce immune responses against liver-metastasized MSS colorectal cancer [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 528.

Synchronous recurrence of concurrent colon adenocarcinoma and dedifferentiated liposarcoma

A 62-year-old man presented with concurrent sigmoid colon adenocarcinoma and small bowel mesenteric dedifferentiated liposarcoma. Following surgical resection of the colon cancer, complete excision of the mesenteric sarcoma and adjuvant folinic acid, fluorouracil and oxaliplatin (FOLFOX) chemotherapy, the patient demonstrated no radiological evidence of disease for more than 2 years. The patient then developed synchronous recurrence of both cancers: the colon cancer metastasised to the liver and a pelvic lymph node, and the liposarcoma recurred in the original location. The patient underwent additional chemotherapy with complete response of the metastatic colon cancer and stable disease for the liposarcoma. The recurrent mesenteric tumour was subsequently resected. Although concurrent cancers have been reported, this unique case of synchronous recurrence raises interesting hypotheses regarding host-tumour interaction and immune surveillance.

Identification of exhausted CD8+ T cells in low tumor mutation burden breast cancer patients

Tumor immunogenicity is generally thought to be correlated with increased tumor mutation burden and the resulting neoantigen driven T cell reactivity to cancer cells. This immunogenicity results in the formation of tumor specific, but exhausted tumor infiltrating CD8+ T cells (TILex). Breast cancer tumors, which are predominantly low mutation burden, are widely viewed as non-immunogenic. Here we demonstrate that subsets of both triple negative and estrogen receptor positive breast cancer patients have primary tumors heavily infiltrated by tumor specific CD8+ TILex. CD8+ TILex in breast cancer patients were demonstrated to coexpress PD-1 and CD39 and showed a significant reduction of IFNγ, TNFα, and IL-2 production capacity. Like melanoma and colorectal CD8+ TILex, CD8+ TILex human breast tumors had increased expression of CD103, CD38, and TIM-3 in addition to loss of KLRG1 and CD127 expression. Similarly, melanoma, colorectal, and breast tumor CD8+ TILex shared transcriptional signatures identified by single cell sequencing. T cell receptor sequencing revealed a distinct repertoire of CD8+ TILex as compared to other CD8+ TILs from the same tumors, suggesting them to be a unique population in response to tumor antigen. Finally, we demonstrated that increased levels of CD8+ TILex in human breast tumors are not associated with higher levels of tumor mutation burden, as assessed by a tumor mutation load oncogene panel. This work suggests that a subset of breast cancer patients have inflamed, tumors associated with the presence of exhausted CD8+ T cells and that these patients may benefit from immunotherapeutic interventions.

Altered phenotypes of tumor-infiltrating B cells in response to exhausted CD8+ T cells

During chronic infections, such as cancer, tumor antigen presentation and inflammation mobilizes a heterogeneous T cell response, consisting of cells in unique states of differentiation and functional capacity. We assayed tumor-infiltrating lymphocytes from human breast, colorectal and melanoma tumors. By flow cytometry, we observed T cells undergoing exhaustion as characterized by a loss of effector functions (IFNy, TNFa, and IL-2) and expressing surface markers PD-1, TIM-3 and CD39. Although this cell intrinsic signature of T cell exhaustion has been well studied, its association with B lymphocytes is still obscure. CXCL13 expression was one of the most significantly upregulated genes in tumor exhausted T cells, as observed by single-cell sequencing. We identified infiltration of CD138+ CD38− plasma cells and CD138−CD38−CD19+ B cells in human breast, colorectal and melanoma tumors. In addition, we observed, by immunohistochemistry, large tertiary lymphoid structures (TLS) in human breast cancer tumors composed of CD20+ B cells and T cells in close proximity. Finally, we evaluated the differential expression of immune modulatory molecules GARP, CD39 and CD73 on B cell subsets from tumors. Further work will investigate the inhibitory or stimulatory role of B cells on tumor-infiltrating T cells.

Human breast tumor-infiltrating CD8+ T cells retain polyfunctionality despite PD-1 expression

Functional CD8⁺ T cells in human tumors play a clear role in clinical prognosis and response to immunotherapeutic interventions. PD-1 expression in T cells involved in chronic infections and tumors such as melanoma often correlates with a state of T-cell exhaustion. Here we interrogate CD8⁺ tumor-infiltrating lymphocytes (TILs) from human breast and melanoma tumors to explore their functional state. Despite expression of exhaustion hallmarks, such as PD-1 expression, human breast tumor CD8⁺ TILs retain robust capacity for production of effector cytokines and degranulation capacity. In contrast, melanoma CD8⁺ TILs display dramatic reduction of cytokine production and degranulation capacity. We show that CD8⁺ TILs from human breast tumors can potently kill cancer cells via bi-specific antibodies. Our data demonstrate that CD8⁺ TILs in human breast tumors retain polyfunctionality, despite PD-1 expression, and suggest that they may be harnessed for effective immunotherapies.

Expression of the checkpoint molecule programmed cell death protein 1 (PD-1) is considered a marker of T cells exhaustion. Here the authors show that CD8T cells isolated from breast cancer patients are perfectly functional despite PD-1 expression while those isolated from melanoma patients are not.

Lymph Node Cellular Dynamics in Cancer and HIV: What Can We Learn for the Follicular CD4 (Tfh) Cells?

Lymph nodes (LNs) are central in the generation of adaptive immune responses. Follicular helper CD4 T (Tfh) cells, a highly differentiated CD4 population, provide critical help for the development of antigen-specific B cell responses within the germinal center. Throughout the past decade, numerous studies have revealed the important role of Tfh cells in Human Immunodeficiency Virus (HIV) pathogenesis as well as in the development of neutralizing antibodies post-infection and post-vaccination. It has also been established that tumors influence various immune cell subsets not only in their proximity, but also in draining lymph nodes. The role of local or tumor associated lymph node Tfh cells in disease progression is emerging. Comparative studies of Tfh cells in chronic infections and cancer could therefore provide novel information with regards to their differentiation plasticity and to the mechanisms regulating their development.