The long and winding road to biomarkers for immunotherapy: a retrospective analysis of samples from patients with triple-negative breast cancer treated with pembrolizumab

BACKGROUND

Immune checkpoint blockade (ICB) in combination with chemotherapy improves outcome of patients with triple-negative breast cancer (TNBC) in metastatic and early settings. The identification of predictive biomarkers able to guide treatment decisions is challenging and currently limited to programmed death-ligand 1 (PD-L1) expression and high tumor mutational burden (TMB) in the advanced setting, with several limitations.

MATERIALS AND METHODS

We carried out a retrospective analysis of clinical-pathological and molecular characteristics of tumor samples from 11 patients with advanced TNBC treated with single-agent pembrolizumab participating in two early-phase clinical trials: KEYNOTE-012 and KEYNOTE-086. Clinical, imaging, pathological [i.e. tumor-infiltrating lymphocytes (TILs), PD-L1 status], RNA sequencing, and whole-exome sequencing data were analyzed. We compared our results with publicly available transcriptomic data from TNBC cohorts from TCGA and METABRIC.

RESULTS

Response to pembrolizumab was heterogeneous: two patients experienced exceptional long-lasting responses, six rapid progressions, and three relatively slower disease progression. Neither PD-L1 nor stromal TILs were significantly associated with response to treatment. Increased TMB values were observed in tumor samples from exceptional responders compared to the rest of the cohort (P = 3.4 × 10-4). Tumors from exceptional responders were enriched in adaptive and innate immune cell signatures. Expression of regulatory T-cell markers (FOXP3, CCR4, CCR8, TIGIT) was mainly observed in tumors from responders except for glycoprotein-A repetitions predominant (GARP), which was overexpressed in tumors from rapid progressors. GARP RNA expression in primary breast tumors from the public dataset was significantly associated with a worse prognosis.

CONCLUSIONS

The wide spectrum of clinical responses to ICB supports that TNBC is a heterogeneous disease. Tumors with high TMB respond better to ICB. However, the optimal cut-off of 10 mutations (mut)/megabase (Mb) may not reflect the complexity of all tumor subtypes, despite its approval as a tumor-agnostic biomarker. Further studies are required to better elucidate the relevance of the tumor microenvironment and its components as potential predictive biomarkers in the context of ICB.

Deciphering the maturation of tertiary lymphoid structures in cancer and inflammatory diseases of the digestive tract using imaging mass cytometry

Persistent inflammation can promote the development of tertiary lymphoid structures (TLS) within tissues resembling secondary lymphoid organs (SLO) such as lymph nodes (LN). The composition of TLS across different organs and diseases could be of pathophysiological and medical interest. In this work, we compared TLS to SLO in cancers of the digestive tract and in inflammatory bowel diseases. Colorectal and gastric tissues with different inflammatory diseases and cancers from the department of pathology of CHU Brest were analyzed based on 39 markers using imaging mass cytometry (IMC). Unsupervised and supervised clustering analyses of IMC images were used to compare SLO and TLS. Unsupervised analyses tended to group TLS per patient but not per disease. Supervised analyses of IMC images revealed that LN had a more organized structure than TLS and non-encapsulated SLO Peyer's patches. TLS followed a maturation spectrum with close correlations between germinal center (GC) markers' evolution. The correlations between organizational and functional markers made relevant the previously proposed TLS division into three stages: lymphoid-aggregates (LA) (CD20+CD21-CD23-) had neither organization nor GC functionality, non-GC TLS (CD20+CD21+CD23-) were organized but lacked GC's functionality and GC-like TLS (CD20+CD21+CD23+) had GC's organization and functionality. This architectural and functional maturation grading of TLS pointed to differences across diseases. TLS architectural and functional maturation grading is accessible with few markers allowing future diagnostic, prognostic, and predictive studies on the value of TLS grading, quantification and location within pathological tissues in cancers and inflammatory diseases.

Abstract 2045: Spatial organization of the immune microenvironment after neoadjuvant treatment of breast cancer

Using the immune system to fight cancer has garnered tangible success, but some treatments, like neoadjuvant chemotherapy (NAC), modulate the immune microenvironment. Recent studies show that the spatial organization of tumor infiltrating lymphocytes (TIL) have greater predictive value than TIL density. The effect of NAC on immune composition and spatial distribution is not fully understood but new insight could help to guide its use in combination with immune therapy and identify patients with potential to derive benefit. We spatially profiled 84 RNA targets (GeoMx®) in a cohort of 12 NAC-treated breast cancer patients (4 Luminal, 4 HER2+ and 4 triple negative), none of whom achieved a pathological complete response. Matched pre- and post-treatment tissue samples were analyzed together with regions of interest (tumor center, invasive margin and TIL aggregates) identified using CD3, CD20, Syto83 and pan-cytokeratin for stromal/tumor segmentation. NAC decreases overall gene expression in breast tumors with the biggest declines seen in tumor promoting (CCND1, AKT1, CTNNB1, EPCAM, VEGFA, KRT and MKI67) and some inflammatory (CXCL10, STAT1 and STAT2) genes (p-value <0.05; other immune related transcripts showed little variation). Expression was compared between patients with a good response (<20% tumor cellularity) and those with a poor response (>50% cellularity). Poor responders expressed higher levels of tumor promoting genes pre-NAC, which remained high after treatment (KRT p=0.023, CTNNB1 p=0.031). No differences were detected in immune genes in the stroma based on patient responsiveness; however, higher antigen presentation and inflammatory gene transcripts were found at the tumor margins of good responders. Post-NAC differences between the margin and center decrease in good responders paralleled by a shift towards higher or equal expression of some inflammatory markers at the tumor center. Poor responders maintain high expression of all immune markers at the margin. A higher number of aggregates (mean n=5 vs n=1.3) were detected in good compared to poor responders together with more tertiary lymphoid structures (mean n=2.4 vs n=0.3) and distinguished by higher immune gene expression (CD8 p=0.046, CCL5 p=0.054, NKG7 p=0.022). NAC induces changes in other cells in the tumor microenvironment while targeting tumor cells. Our data show that spatial analysis of gene expression comparing good and poor responders (without a pathological complete response) reveal that tumor cells in the latter retain expression of tumor promoting genes while the immune compartment remains excluded. Good responders are characterized by a decrease in tumor promoting genes in parallel with lymphoid aggregates, including TLS, of active immune cells in the stroma and at the tumor center. These findings suggest that tailoring adjuvant treatment between good and poor responding patients might be warranted.

Citation Format: Noémie Thomas, Soizic Garaud, Mireille Langouo, Ioannis Zerdes, Doïna Sofronii, Anaïs Boisson, Theodoros Foukakis, Alexandre De Wind, Roberto Salgado, Ahmad Awada, Karen Willard-Gallo. Spatial organization of the immune microenvironment after neoadjuvant treatment of 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 2045.

Fluorescent Multiplex Immunohistochemistry Coupled With Other State-Of-The-Art Techniques to Systematically Characterize the Tumor Immune Microenvironment

Our expanding knowledge of the interactions between tumor cells and their microenvironment has helped to revolutionize cancer treatments, including the more recent development of immunotherapies. Immune cells are an important component of the tumor microenvironment that influence progression and treatment responses, particularly to the new immunotherapies. Technological advances that help to decipher the complexity and diversity of the tumor immune microenvironment (TIME) are increasingly used in translational research and biomarker studies. Current techniques that facilitate TIME evaluation include flow cytometry, multiplex bead-based immunoassays, chromogenic immunohistochemistry (IHC), fluorescent multiplex IHC, immunofluorescence, and spatial transcriptomics. This article offers an overview of our representative data, discusses the application of each approach to studies of the TIME, including their advantages and challenges, and reviews the potential clinical applications. Flow cytometry and chromogenic and fluorescent multiplex IHC were used to immune profile a HER2+ breast cancer, illustrating some points. Spatial transcriptomic analysis of a luminal B breast tumor demonstrated that important additional insight can be gained from this new technique. Finally, the development of a multiplex panel to identify proliferating B cells, Tfh, and Tfr cells on the same tissue section demonstrates their co-localization in tertiary lymphoid structures.

Functional Th1-oriented T follicular helper cells that infiltrate human breast cancer promote effective adaptive immunity

We previously demonstrated that tumor-infiltrating lymphocytes (TIL) in human breast cancer sometimes form organized tertiary lymphoid structures (TLS) characterized by CXCL13-producing T follicular helper (Tfh) cells. The present study found that CD4+ Tfh TIL, CD8+ TIL, and TIL-B, colocalizing in TLS, all express the CXCL13 receptor CXCR5. An ex vivo functional assay determined that only activated, functional Th1-oriented Tfh TIL (PD-1hiICOSint phenotype) provide help for immunoglobulin and IFN-γ production. A functional Tfh TIL presence signals an active TLS, characterized by humoral (immunoglobulins, Ki-67+ TIL-B in active germinal centers) and cytotoxic (GZMB+CD8+ and GZMB+CD68+ TIL plus Th1 gene expression) immune responses. Analysis of active versus inactive TLS in untreated patients revealed that the former are associated with positive clinical outcomes. TLS also contain functional T follicular regulatory (Tfr) TIL, which are characterized by a CD25+CXCR5+GARP+FOXP3+ phenotype and a demethylated FOXP3 gene. Functional Tfr inhibited functional Tfh activities via a glycoprotein A repetitions predominant (GARP)-associated TGF-β-dependent mechanism. The activity of tumor-associated TLS was dictated by the relative balance between functional Tfh TIL and functional Tfr TIL. These data provide mechanistic insight into TLS processes orchestrated by functional Th1-oriented Tfh TIL, including TIL-B and CD8+ TIL activation and immunological memory generation. Tfh TIL, regulated by functional Tfr TIL, are an expected key target of PD-1/PD-L1 blockade.

Downregulation of the FTO m6A RNA demethylase promotes EMT-mediated progression of epithelial tumors and sensitivity to Wnt inhibitors

Post-transcriptional modifications of RNA constitute an emerging regulatory layer of gene expression. The demethylase fat mass- and obesity-associated protein (FTO), an eraser of N6-methyladenosine (m6A), has been shown to play a role in cancer, but its contribution to tumor progression and the underlying mechanisms remain unclear. Here, we report widespread FTO downregulation in epithelial cancers associated with increased invasion, metastasis and worse clinical outcome. Both in vitro and in vivo, FTO silencing promotes cancer growth, cell motility and invasion. In human-derived tumor xenografts (PDXs), FTO pharmacological inhibition favors tumorigenesis. Mechanistically, we demonstrate that FTO depletion elicits an epithelial-to-mesenchymal transition (EMT) program through increased m6A and altered 3'-end processing of key mRNAs along the Wnt signaling cascade. Accordingly, FTO knockdown acts via EMT to sensitize mouse xenografts to Wnt inhibition. We thus identify FTO as a key regulator, across epithelial cancers, of Wnt-triggered EMT and tumor progression and reveal a therapeutically exploitable vulnerability of FTO-low tumors.

Persistent anti-tumor response in cancer patients experiencing pneumonitis related to immune checkpoint blockade

Background: Immunotherapy in the form of immune checkpoint inhibition (ICI) is now well established as acornerstone for treating many advanced malignancies. Nevertheless, as the number of indications for checkpoint inhibitors increases, so does the risk of immune-related adverse events (irAEs).Methods: We report two patient cases who, after being treated by an anti-programmed cell death 1 (PD-1), presented with grade III dyspnea due to pneumonitis.Discussion: Immunotherapy was discontinued and the patients required treatment with systemic corticosteroids. At the time of writing, both patients are still in complete response (CR), more than 1year beyond immunotherapy discontinuation. We discuss our cases with regard to recent literature reports on immune-related pneumonitis and persistence of response beyond discontinuation.

Abstract PS17-21: Characterization of the immune microenvironment in ductal carcinoma in situ of the breast

Background Ductal carcinoma in situ (DCIS) is considered a low-risk disease of the breast. Current increases in its incidence have resulted in many women either being under- or over-treated due to our limited findings on independent prognostic and predictive biomarkers. The Van Nuys Prognostic Index, based on tumor size, margin status, grade and age, is one tool used in treatment decisions. Patients with a low score show no significant benefit from radiotherapy, in contrast to those with an intermediate score, while patients with high scores should be considered for mastectomy. In contrast, for invasive ductal carcinoma (IDC) of the breast there is a strong consensus for the prognostic and predictive value of tumor infiltrating lymphocytes (TIL). As very little is known about TIL in DCIS, the goal of this study is to fully characterize the immune infiltrate and compare it to IDC, examine differences in the balance between effector and regulatory subpopulations and potentially discover new biomarkers for risk stratification.

Material and Methods Fourteen patients were prospectively enrolled at the St. Luc hospital in Brussels, including 4 pure DCIS, 5 mixt DCIS and IDC, and 5 normal breast tissues. Formalin-fixed paraffin-embedded sections were stained with three fluorescent multiplex immunohistochemistry (mIHC) panels that combined antibodies to CD45, CD4, CD8, CD20, FOXP3, CD68, GZMB, PD-1, Ki67 and cytokeratin. InForm® Tissue Finder™ software and PhenoptrReports (Akoya Biosciences®) were employed for TIL quantification and spatial distribution. Freshly resected DCIS tissues were used to isolate tumor-infiltrating CD4 and CD8 T cells for single cell RNAseq analysis to determine the T cell clonotypes present (A. Devaux’s poster)

Results Our analyses reveal the DCIS stroma has a significant immune infiltrate dominated by CD4+ helper T cells and B cells (140 and 115 cells/mm2, respectively) followed by CD8+ cytotoxic T cells (72 cells/mm2), regulatory T cells (Treg) (27 cells/mm2) and to a lesser extent macrophages (23 cells/mm2). The immune pattern in DCIS is similar to IDC except there are fewer macrophages in the tumor areas and Treg increase in the stroma. Tumor areas are generally less infiltrated than the stroma but some DCIS cells are in direct contact with T cells and macrophages. Spatial distribution analysis within a radius of 30 μm confirms that Treg are in close proximity to the DCIS cells and in the proximity of CD4+ helper and CD8+ cytotoxic T cells. Moreover, proliferating GZMB+ cells, mainly CD8+ cytotoxic T cells, were observed in direct contact with DCIS cells. Only one patient out of 4 had PD1+ TIL in the stroma. A comparison of pure and mixt DCIS reveals lower stromal infiltration by T and B cells in the former, which is also associated with an increase in macrophages. Finally, the abundance of stromal TIL was frequently organized in tertiary lymphoid structures (TLS), composed by a B cell follicle surrounded by a T cell zone containing both CD4+ helper and CD8+ cytotoxic T cells. TLS were characterized by the presence of proliferating B cells and PD1high T follicular helper cells. FOXP3+ and GZMB+ cells were also observed in the T cell zone.

Conclusions Examination of the immune infiltrate in DCIS shows an abundance of helper T cells, B cells and active cytotoxic T cells in association with stromal TLS. These observations reveal an active tumor immune microenvironment in DCIS and suggest that the immune response plays an active role in DCIS pathogenesis.

Citation Format: Soizic Garaud, Alix Devaux, Anais Boisson, Céline Naveaux, Pierre Coulie, Ahmad Awada, Karen Willard-Gallo. Characterization of the immune microenvironment in ductal carcinoma in situ of the breast [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 PS17-21.

Inhibition of RANK signaling in breast cancer induces an anti-tumor immune response orchestrated by CD8+ T cells

Most breast cancers exhibit low immune infiltration and are unresponsive to immunotherapy. We hypothesized that inhibition of the receptor activator of nuclear factor-κB (RANK) signaling pathway may enhance immune activation. Here we report that loss of RANK signaling in mouse tumor cells increases leukocytes, lymphocytes, and CD8⁺ T cells, and reduces macrophage and neutrophil infiltration. CD8⁺ T cells mediate the attenuated tumor phenotype observed upon RANK loss, whereas neutrophils, supported by RANK-expressing tumor cells, induce immunosuppression. RANKL inhibition increases the anti-tumor effect of immunotherapies in breast cancer through a tumor cell mediated effect. Comparably, pre-operative single-agent denosumab in premenopausal early-stage breast cancer patients from the Phase-II D-BEYOND clinical trial (NCT01864798) is well tolerated, inhibits RANK pathway and increases tumor infiltrating lymphocytes and CD8⁺ T cells. Higher RANK signaling activation in tumors and serum RANKL levels at baseline predict these immune-modulatory effects. No changes in tumor cell proliferation (primary endpoint) or other secondary endpoints are observed. Overall, our preclinical and clinical findings reveal that tumor cells exploit RANK pathway as a mechanism to evade immune surveillance and support the use of RANK pathway inhibitors to prime luminal breast cancer for immunotherapy.

Receptor activator of nuclear factor-κB (RANK)/RANK-ligand (RANKL) signaling regulates the tumor-immune crosstalk. Here the authors show that systemic RANKL inhibition promotes CD8 + T cell infiltration in patients with early breast cancer and that loss of RANK signaling in tumor cells drives a T cell-dependent anti-tumor response in preclinical models.

Abstract 3853: The anti-tumor immune responses by active and quiescent tertiary lymphoid structures to breast cancer

There is a growing interest in active immune responses generated by tertiary lymphoid structures (TLS) arising in solid tumors; however, their clinical impact in breast cancer (BC) remains unclear. Several studies show that transcription factors contribute to TLS formation via their regulation of cytokine and chemokine production. The Forkhead box (FOX) protein 1 (FOXP1) has been shown to play critical roles in regulating immune cells, including our recent work revealing its effects on TIL migration. These data lead us to further investigate FOXP1 expression in tumor infiltrating lymphocytes (TIL) and TLS. We identify two types of TLS based on FOXP1 expression: 1) those that contain a germinal center (GC+) and those that do not (GC-). Comparative analysis of FOXP1 expression in secondary lymphoid organs, including more immune active tonsils (many GC) and less immune active spleens (primarily without GC) confirm differences in FOXP1 expression associated with GC. In BC, TLS containing tumors were more frequently GC- than GC+ (n=49), with triple-negative tumors having higher numbers of GC+ TLS compared to luminal or HER2+ tumors. Immunofluorescence and multiplex immunohistochemistry was used to closely examine the GC+ and GC- TLS, finding an immune active profile in the former, characterized by T follicular helper cells (PD1+CD4+ T), mature dendritic cells (CD21+ and CD23+), actively proliferating (Ki67+) B cells undergoing immunoglobulin (Ig) class switch recombination (AID+) and a plasma cell presence (CD138+). Analysis of Ig's in the primary tumor supernatants revealed that BC with ≥1 GC+ TLS (n=20) were characterized by increases in total Ig, IgG1, IgG2 and IgA, reflecting active humoral immunity, compared to BC containing only GC- TLS (n=29). Gene expression analysis of individual micro-dissected TLS demonstrated upregulation of Th1, Th2 and Tfh immune genes in the GC+ compared to the GC- TLS, suggesting the former also sustain cell-mediated immune responses. Immune infiltrates in tumors with ≥1 GC+ TLS are specifically characterized by high global TIL, CD3+, CD4+ or CD8+ T cell TIL and CD20+ TIL-B (n=29). Analysis of BC TIL spatial distribution identified increased stromal TIL (all subpopulations) while intratumoral TIL increases were predominantly CD3+ and CD8+ T cell TIL in tumors with GC+ TLS. Overall, our data indicate that GC+ TLS house active immune responses in BC while GC- TLS are quiescent.

Citation Format: Pushpamali De Silva, Soizic Garaud, Cinzia Solinas, Grégory Noël, Mireille Langouo Fontsa, Anaïs Boisson, Alexandre de Wind, Vinu Jose, Gert Van den Eynden, Noemie Thomas, Hugues Duvillier, Céline Naveaux, Ligia Craciun, Dominique Bron, Martine Piccart-Gebhart, Denis Larsimont, Karen Willard-Gallo. The anti-tumor immune responses by active and quiescent tertiary lymphoid structures to breast cancer [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 3853.

Abstract PR10: Active and quiescent tertiary lymphoid structures, differentiated using FOXP1 expression, play a role in immunity to breast cancer

Interest is growing in active immune responses generated by tertiary lymphoid structures (TLS) arising in solid tumors; however, their clinical impact in breast cancer (BC) remains unclear. Several studies show that transcription factors contribute to TLS formation via their regulation of cytokine and chemokine production. The Forkhead box (FOX) protein 1 (FOXP1) has been shown to play critical roles in regulating immune cells, including our recent work revealing its effects on TIL migration. These data lead us to further investigate FOXP1 expression in tumor-infiltrating lymphocytes (TIL) and TLS. We identify two types of TLS based on FOXP1 expression: 1) those that contain a germinal center (GC+) and those that do not (GC-). Comparative analysis of FOXP1 expression in secondary lymphoid organs, including more immune active tonsils (many GC) and less immune active spleens (primarily without GC), confirms differences in FOXP1 expression associated with GC. In BC, TLS-containing tumors were more frequently GC- than GC+ (n=49), with triple-negative tumors having higher numbers of GC+ TLS compared to luminal or HER2+ tumors. Immunofluorescence and multiplex immunohistochemistry was used to closely examine the GC+ and GC- TLS, finding an immune active profile in the former, characterized by T follicular helper cells (PD1+CD4+ T), mature dendritic cells (CD21+ and CD23+), actively proliferating (Ki67+) B cells undergoing immunoglobulin (Ig) class switch recombination (AID+) and a plasma cell presence (CD138+). Analysis of Igs in primary tumor supernatants revealed that BC with ≥1 GC+ TLS (n=20) were characterized by increases in total Ig, IgG1, IgG2, and IgA, reflecting active humoral immunity, compared to BC containing only GC- TLS (n=29). Gene expression analysis of individual microdissected TLS demonstrated upregulation of Th1, Th2, and Tfh immune genes in the GC+ compared to the GC- TLS, suggesting the former also sustain cell-mediated immune responses. Immune infiltrates in tumors with ≥1 GC+ TLS are specifically characterized by high global TIL, CD3+, CD4+ or CD8+ T cell TIL and CD20+ TIL-B (n=29). Analysis of BC TIL spatial distribution identified increased stromal TIL (all subpopulations) while intratumoral TIL increases were predominantly CD3+ and CD8+ T cell TIL in tumors with GC+ TLS. Overall, our data indicate that GC+ TLS house active immune responses in BC while GC- TLS are quiescent.

This abstract is also being presented as Poster B99.

Citation Format: Pushpamali De Silva, Soizic Garaud, Cinzia Solinas, Grégory Noël, Mireille Langouo Fontsa, Anaïs Boisson, Alexandre de Wind, David Venet, Gert Van den Eynden, Hugues Duvillier, Céline Naveaux, Ligia Craciun, Dominique Bron, Martine Piccart-Gebhart, Denis Larsimont, Karen Willard-Gallo. Active and quiescent tertiary lymphoid structures, differentiated using FOXP1 expression, play a role in immunity to breast cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr PR10.

Retrospective analysis of the immunogenic effects of intra-arterial locoregional therapies in hepatocellular carcinoma: a rationale for combining selective internal radiation therapy (SIRT) and immunotherapy

Background

Immunotherapy represents a promising option for treatment of hepatocellular carcinoma (HCC) in cirrhotic patients but its efficacy is currently inconsistent and unpredictable. Locoregional therapies inducing immunogenic cell death, such as transarterial chemoembolization (TACE) or selective internal radiation therapy (SIRT), have the potential to act synergistically with immunotherapy. For the development of new approaches combining locoregional treatments with immunotherapy, a better understanding of the respective effects of TACE and SIRT on recruitment and activation of immune cells in HCC is needed. To address this question, we compared intra-tumor immune infiltrates in resected HCC after preoperative treatment with TACE or SIRT.

Methods

Data fromr patients undergoing partial hepatectomy for HCC, without preoperative treatment (SURG, n = 32), after preoperative TACE (TACE, n = 16), or preoperative SIRT (n = 12) were analyzed. Clinicopathological factors, tumor-infiltrating lymphocytes (TILs), CD4⁺ and CD8⁺ T cells, and granzyme B (GZB) expression in resected HCC, and postoperative overall and progression-free survival were compared between the three groups.

Results

Clinicopathological and surgical characteristics were similar in the three groups. A significant increase in TILs, CD4⁺ and CD8⁺ T cells, and GZB expression was observed in resected HCC in SIRT as compared to TACE and SURG groups. No difference in immune infiltrates was observed between TACE and SURG patients. Within the SIRT group, the dose of irradiation affected the type of immune infiltrate. A significantly higher ratio of CD3⁺ cells was observed in the peri-tumoral area in patients receiving < 100 Gy, whereas a higher ratio of intra-tumoral CD4⁺ cells was observed in patients receiving > 100 Gy. Postoperative outcomes were similar in all groups. Irrespective of the preoperative treatment, the type and extent of immune infiltrates did not influence postoperative survival.

Conclusions

SIRT significantly promotes recruitment/activation of intra-tumor effector-type immune cells compared to TACE or no preoperative treatment. These results suggest that SIRT is a better candidate than TACE to be combined with immunotherapy for treatment of HCC. Evaluation of the optimal doses for SIRT for producing an immunogenic effect and the type of immunotherapy to be used require further evaluation in prospective studies.

Abstract P5-04-12: Functional CXCR5+CD4+ follicular helper T cells in breast cancer associated tertiary lymphoid structures signal active immune responses at the tumor site

Background: The association between tumor infiltrating lymphocytes (TIL) and positive clinical outcomes in breast cancer (BC) is now commonly recognized. Previous work from our laboratory demonstrated that TIL can organize in tertiary lymphoid structures (TLS) in BC-associated stroma. We further showed that CXCL13, produced by specialized CD4+ T follicular helper (TfhX13) cell, is an important TLS chemoattractant and associated with positive clinical outcomes. The current study investigated how immune cell functionally and regulation in TLS contributes to immune responses in BC.

Methodology: We prospectively collected fresh primary BC tissues and prepared enzyme-free homogenates to produce TIL suspensions and tumor supernatants for flow cytometry and cytokine/chemokine/immunoglobulin (Ig) analysis, respectively. Matching formalin-fixed paraffin-embedded tumor tissues were analyzed using dual immunohistochemistry (IHC) and immunofluorescence (IF) confocal microscopy or multiplex IHC.

Results: We show that CXCR5, the CXCL13 receptor, is expressed on subpopulations of CD4+ (Tfh) and CD8+ T cell TIL as well as the majority of TIL-B, with all CXCR5+ TIL co-localizing in TLS. The functional activities of Tfh TIL, evaluated using an in vitro assay with allogeneic human splenic B cells, reveals that PD-1hiICOS+ Tfh TIL (in some triple negative and HER2+ but not luminal BC) can provide help to TIL-B for Ig production. This observation is strengthened by additional data showing: 1) a correlation between functional (PD-1hiICOS+) Tfh TIL densities and IgG concentrations in primary BC supernatants; 2) a strong correlation between PD-1+ Tfh TIL and Ki67+ TIL-B in BC-associated TLS; and 3) cell-to-cell contact between Tfh TIL and TIL-B in TLS with active germinal centers. PD-1hiICOS+ (functional) and PD-1lo/intICOS− (non-functional) Tfh TIL were sorted for mRNA analysis with functional Tfh TIL expressing higher levels of IL-21, IFNγ and CXCL13. Higher IFNγ expression by PD-1hiICOS+ Tfh TIL suggests their functional Th1 orientation. CXCR5+ T follicular regulatory (Tfr) TIL were also detected in TLS and shown to express, CD25, demethylated FOXP3, and GARP, a marker of active TGFβ. Analyzing the ratio between Tfh and GARP+ Tfr TIL revealed that when the balance favors Tfh TIL, IgG production is increased. This Tfh/Tfr ratio was also correlated with activated CXCR5+CD8+ TIL in TLS. Multiplex IHC identified the positioning of CXCR5+ TIL subpopulations and demonstrated there are important cell-to-cell contacts between these subpopulations in active TLS.

Conclusions: Our data show that Tfh TIL subpopulations play major roles in the functionality of BC-associated TLS. The balance between functionally active and regulatory CXCR5+ Tfh TIL together with active CXCR5+CD8+ TIL and CXCR5+ TIL-B appears to regulate immune activities in the tumor microenvironment. Tumors with functional Tfh TIL are linked to a more robust stromal and intratumoral infiltrate together with a ratio of active TLS &gt;1. Thus, while TIL density scores provide important primary insight on immune activity in BC, their organization and subpopulation balances may offer key information for fine-tuning treatment selection options, particularly for immune-based therapies.

Citation Format: Karen Willard-Gallo, Gregory Noel, Mireille Langouo Fontsa, Soizic Garaud, Alexandre de Wind, Gert Van den Eynden, Roberto Salgado, Anais Boisson, Celine Naveaux, Hugues Duvillier, Ligia Craciun, Martine Piccart-Gebhart, Denis Larsimont. Functional CXCR5+CD4+ follicular helper T cells in breast cancer associated tertiary lymphoid structures signal active immune responses at the tumor site [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-12.

Clinical significance of CD73 in triple-negative breast cancer: multiplex analysis of a phase III clinical trial

Background

CD73 is an ecto-enzyme that promotes tumor immune escape through the production of immunosuppressive extracellular adenosine in the tumor microenvironment. Several CD73 inhibitors and adenosine receptor antagonists are being evaluated in phase I clinical trials.

Patients and methods

Full-face sections from formalin-fixed paraffin-embedded primary breast tumors from 122 samples of triple-negative breast cancer (TNBC) from the BIG 02-98 adjuvant phase III clinical trial were included in our analysis. Using multiplex immunofluorescence and image analysis, we assessed CD73 protein expression on tumor cells, tumor-infiltrating leukocytes and stromal cells. We investigated the associations between CD73 protein expression with disease-free survival (DFS), overall survival (OS) and the extent of tumor immune infiltration.

Results

Our results demonstrated that high levels of CD73 expression on epithelial tumor cells were significantly associated with reduced DFS, OS and negatively correlated with tumor immune infiltration (Spearman's R= -0.50, P < 0.0001). Patients with high levels of CD73 and low levels of tumor-infiltrating leukocytes had the worse clinical outcome.

Conclusions

Taken together, our study provides further support that CD73 expression is associated with a poor prognosis and reduced anti-tumor immunity in human TNBC and that targeting CD73 could be a promising strategy to reprogram the tumor microenvironment in this BC subtype.

Tumor-Derived Thymic Stromal Lymphopoietin Expands Bone Marrow B-cell Precursors in Circulation to Support Metastasis

Immature B cells in the bone marrow emigrate into the spleen during adult lymphopoiesis. Here, we report that emigration is shifted to earlier B-cell stages in mice with orthotopic breast cancer, spontaneous ovarian cancer, and possibly in human breast carcinoma. Using mouse and human bone marrow aspirates and mouse models challenged with highly metastatic 4T1 breast cancer cells, we demonstrated that this was the result of secretion of thymic stromal lymphopoietin (TSLP) by cancer cells. First, TSLP downregulated surface expression of bone marrow (BM) retention receptors CXCR4 and VLA4 in B-cell precursors, increasing their motility and, presumably, emigration. Then, TSLP supported peripheral survival and proliferation of BM B-cell precursors such as pre-B-like cells. 4T1 cancer cells used the increased pool of circulating pre-B-like cells to generate metastasis-supporting regulatory B cells. As such, the loss of TSLP expression in cancer cells alone or TSLPR deficiency in B cells blocked both accumulation of pre-B-like cells in circulation and cancer metastasis, implying that the pre-B cell-TSLP axis can be an attractive therapeutic target. SIGNIFICANCE: Cancer cells induce premature emigration of B-cell precursors from the bone marrow to generate regulatory B cells.

Tumor infiltrating B-cells signal functional humoral immune responses in breast cancer

Tumor-infiltrating B-cells (TIL-B) in breast cancer (BC) have previously been associated with improved clinical outcomes; however, their role(s) in tumor immunity is not currently well known. This study confirms and extends the correlation between higher TIL-B densities and positive outcomes through an analysis of HER2-positive and triple-negative BC patients from the BIG 02-98 clinical trial (10yr mean follow-up). Fresh tissue analyses identify an increase in TIL-B density in untreated primary BC compared to normal breast tissues, which is associated with global, CD4+ and CD8+ TIL, higher tumor grades, higher proliferation and hormone receptor negativity. All B-cell differentiation stages are detectable but significant increases in memory TIL-B are consistently present. BC with higher infiltrates are specifically characterized by germinal center TIL-B, which in turn are correlated with TFH TIL and antibody-secreting TIL-B principally located in tertiary lymphoid structures. Some TIL-B also interact directly with tumor cells. Functional analyses reveal TIL-B are responsive to BCR stimulation ex vivo, express activation markers and produce cytokines and immunoglobulins despite reduced expression of the antigen-presenting molecules HLA-DR and CD40. Overall, these data support the concept that ongoing humoral immune responses are generated by TIL-B and help to generate effective anti-tumor immunity at the tumor site.

Immune Infiltration in Invasive Lobular Breast Cancer

Background

Invasive lobular breast cancer (ILC) is the second most common histological subtype of breast cancer after invasive ductal cancer (IDC). Here, we aimed at evaluating the prevalence, levels, and composition of tumor-infiltrating lymphocytes (TILs) and their association with clinico-pathological and outcome variables in ILC, and to compare them with IDC.

Methods

We considered two patient series with TIL data: a multicentric retrospective series (n = 614) and the BIG 02-98 study (n = 149 ILC and 807 IDC). We compared immune subsets identified by immuno-histochemistry in the ILC (n = 159) and IDC (n = 468) patients from the Nottingham series, as well as the CIBERSORT immune profiling of the ILC (n = 98) and IDC (n = 388) METABRIC and The Cancer Genome Atlas patients. All ILC/IDC comparisons were done in estrogen receptor (ER)–positive/human epidermal growth factor receptor 2 (HER2)–negative tumors. All statistical tests were two-sided.

Results

TIL levels were statistically significantly lower in ILC compared with IDC (fold-change = 0.79, 95% confidence interval = 0.70 to 0.88, P < .001). In ILC, high TIL levels were associated with young age, lymph node involvement, and high proliferative tumors. In the univariate analysis, high TIL levels were associated with worse prognosis in the retrospective and BIG 02-98 lobular series, although they did not reach statistical significance in the latter. The Nottingham series revealed that the levels of intratumoral but not total CD8⁺ were statistically significantly lower in ILC compared with IDC. Comparison of the CIBERSORT profiles highlighted statistically significant differences in terms of immune composition.

Conclusions

This study shows differences between the immune infiltrates of ER-positive/HER2-negative ILC and IDC in terms of prevalence, levels, localization, composition, and clinical associations.

Abstract 3132: Immune regulatory gene expression and clinical outcome in the NeoALTTO trial

Background: The level of immune suppression in an individual breast cancer (BC) patient is relevant for having a major benefit from treatments that act via or are directed to the immune response, such as anti-HER2 agents and immune checkpoint molecules, respectively. The link(s) between the tumor immune microenvironment and treatment responses has been investigated in HER2-positive BC. This study analyzed the association between baseline expression of genes regulating T cell activities (PD1, CTLA4, LAG3, TIM3, PDL1, PDL2, FOXP3, IL10, TGFβ (1-3), FOXP1 and other related genes) and pathologic complete response (pCR) rates in the NeoALTTO trial. Methods: NeoALTTO randomized early-stage HER2-positive BC patients to neoadjuvant trastuzumab (T), lapatinib (L) or T+L for 6 weeks followed by 12 weeks of concurrent paclitaxel. Anthracyclines were given after surgery (FEC). Patients with RNA sequencing data from their baseline tumor samples (N=254 patients out of 455 from the original cohort) were included in the current study. The primary endpoint, pCR, was defined as ypT0/is ypN0. Logistic regression was used for analysis of pCR. Cox regression univariate and multivariate (adjusted for clinicopathological parameters and treatment arms) analyses were performed. Results: In the total cohort analyzed, high PD1 (odds ratio, OR: 1.4, P=0.03), PDL2 (OR: 1.4, P=0.04), CTLA4 (OR: 1.4, P=0.03) and TGFβ3 (OR: 1.4, P=0.02) expression was associated with an increased probability of achieving pCR at the multivariate analysis. ERBB2 (HER2) expression was associated with pCR in the three arms (T: OR: 2.7, P=0.02; L: OR: 2.3, P=0.01; T+L: OR: 5, P&lt;0.001). Additionally in the T+L arm, PAM50 HER2-enriched subtype (OR: 2.9, P=0.03), as well as immune genes PD1 (OR: 2.1, P=0.01), PDL1 (OR: 1.8, P=0.03) and CTLA4 (OR: 2; P=0.01), were also associated with pCR. Conclusions: In the NeoALTTO population examined, PD1, PDL2, CTLA-4 and TGFβ3 expression at diagnosis were all associated with improved pCR rates after anti-HER2 treatment. The effect of these treatments seemed to be dependent on HER2 expression levels, which was particularly relevant in the T+L arm. These observations confirm previous findings that link immune infiltrates to higher pCR rates, demonstrate the clinical significance of the PD-1 pathway and additionally show that CTLA-4 and TGFβ3 could also be important in early stage HER2-positive BC. The association of tumors linked with immune regulatory gene expression with positive responses to neoadjuvant anti-HER2 agents suggests that they act in a way that reinvigorates the antitumor immunity in the face of tumor-mediated suppression. Patients whose tumors highly express these genes may be good candidates for immunotherapy before the start or after the neoadjuvant treatment when residual disease is detected at surgery, although these hypotheses require further confirmation.

Citation Format: Cinzia Solinas, Pushpamali De Silva, David Venet, Soizic Garaud, Chunyan Gu-Trantien, Florentine Hilbers, Evandro de Azambuja, Olena Werner, Lorena De la Peña, Amylou Dueck, Serena Di Cosimo, Istvan Lang, Jens Huober, Sherko Küemmel, Carsten Denkert, Roberto Salgado, Christos Sotiriou, Martine Piccart-Gebhart, Debora Fumagalli, Karen Willard-Gallo. Immune regulatory gene expression and clinical outcome in the NeoALTTO trial [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 3132.

Abstract 3995: BACH2 and PRDM1 gene expression changes in T and B cells according to age of healthy individuals and significance in chronic lymphocytic leukemia patients

Background: Aging is a risk factor for developing malignant hemopathies including chronic lymphocytic leukemia (CLL). We evaluated the relevance of BACH2 and PRDM1 gene expression in the aging of immune cells and the immunodeficiency associated with CLL.

Methods: Peripheral blood mononuclear cells were isolated from untreated CLL patients (n=41) and age-matched healthy donors (HD; n=60). T and B cells were purified (95%-99%) by magnetic isolation. BACH2, PRDM1, PD1, PDL1 and CDKN2A (p16INK4A) transcripts were quantified using RT-qPCR. ß-galactosidase activity was measured by flow cytometry. Cell apoptosis was analyzed after intracellular oxidative stress induced by etoposide treatment. ChIP-qPCR was done to find BACH2-apoptotic target genes in purified CD4+ T cells from HDs with/without etoposide treatment. Prognostic value of BACH2 and PRDM1 expression in purified CD19+ B cells was analyzed retrospectively in a cohort of CLL patients (n= 270), and correlated with clinical parameters.

Results: BACH2 expression in HDs is significantly downregulated while PRDM1 expression increased in CD4+, CD8+ T and CD19+ B cells according to age groups. BACH2 expression is further reduced in T and B cells from CLL patients compared to age-matched HDs. Also, PRDM1 is significantly upregulated in T cells from CLL patients but not in leukemic B cells. PD1 expression is significantly upregulated in T cells in the older vs younger HDs and also in CLL patients compared with age-matched HDs. High PDL1 expression is also strongly correlated with increased age in HD B cells with a further increase detected in leukemic B cells. A strong inverse correlation was observed between BACH2 and PD1 in T cells; and between BACH2 and PDL1 in B cells from HDs. We also analyzed the link between BACH2 expression and senescence markers; CDKN2A and ß-galactosidase. CDKN2A expression inversely correlated with BACH2 in CD4+, CD8+ T and CD19+ B cells. ß-galactosidase activity showed an increase compared to BACH2 deficient lymphocytes in older compared to young HDs, suggesting that BACH2 deficiency leads to the accumulation of senescent cells. A strong correlation was observed between age-related BACH2 downregulation and a decrease in CD4+ T and CD19+ B cell apoptosis after etoposide treatment. ChIP-qPCR assay confirmed that BACH2 binds to genes involved in apoptosis and after etoposide treatment, BACH2 binding was repressed. In our retrospective cohort, increased BACH2 expression was correlated with improved treatment-free survival (p=0.0352).

Conclusion: Decrease of BACH2 and increase of PRDM1, PD1 and PDL1 in T and B cells from CLL patients and aged-matched HDs, are significantly correlated with aging and could be part of immunosenescence. Involvement of BACH2 in resistance to drug-induced apoptosis of HD lymphocytes was documented and is currently investigated in the CLL cohort.

Citation Format: Pushpamali De Silva, Vu Luan Dang Chi, Basile Stamatopoulos, Soizic Garaud, Vincent Thibaud, Hugues Duvillier, Jean-Nicolas Lodewyckx, Catherine Sibille, Karen Willard-Gallo, Dominique Bron. BACH2 and PRDM1 gene expression changes in T and B cells according to age of healthy individuals and significance in chronic lymphocytic leukemia patients [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 3995.

BRCA gene mutations do not shape the extent and organization of tumor infiltrating lymphocytes in triple negative breast cancer

This study investigated the prevalence of TIL subpopulations, TLS, PD-1 and PD-L1 in tumors from TNBC patients harboring wild-type or mutated BRCA1 or BRCA2 germline genes. This TNBC cohort included 85% TIL-positive (≥10%) tumors with 21% classified as TIL^hi (≥50%). Interestingly, the BRCA^mut group had a significantly higher incidence of TIL^pos tumors compared to the BRCA^wt group (P = 0.037). T cells were dominant in the infiltrate but no statistically significant differences were detected between BRCA^wt and BRCA^mut for CD3⁺, CD4⁺ and CD8⁺ T cells or CD20⁺ B cells. TLS were detected in 74% of tumors but again no significant differences between the BRCA groups. PD-1 expression was observed in 33% and PD-L1 in 53% (any cell, cut-off ≥1%) tumors for the entire TNBC cohort. PD-1 expression correlated with PD-L1 and both with TIL and TLS but was not associated with BRCA mutational status. Our analyses reveal that BRCA^wt and BRCA^mut TNBC are similar except for a significant increase of TIL^pos tumors in the BRCA^mut group. While BRCA gene mutations may not directly drive immune infiltration, the greater number of TIL^pos tumors could signal greater immunogenicity in this group.

Abstract PD5-10: Immune characterization of matched primary and multiple metastatic samples issued from an institutional autopsy cohort

Introduction

While immune infiltrates have already been extensively characterized in primary tumors (P), data on breast cancer metastases (M) remains limited. To this end we quantified and qualified the immune cells in a unique cohort of multiple matched P and M samples selected from an institutional breast cancer autopsy cohort.

Patients and methods

Twenty-three patients were selected from an institutional autopsy program (Semmelweis University, Budapest, Hungary) based on matched P and M sample availability (124 samples). All samples were centrally characterized for estrogen (ER), progesterone (PR) and HER2 receptors. The primary molecular subtypes were as follows: 9 ER+/PR+/HER2-, 8 triple negative and 6 HER2+. Ten patients relapsed ≤1 year after diagnosis and were further referred to as “early relapsers”, as opposed to the remaining qualified as “late relapsers”. Immunohistochemistry (IHC) was carried out against CD3/CD20 and CD4/CD8 in 21 patients (119 samples). Tumor infiltrating lymphocytes (TILs) were assessed on hematoxylin and eosin (H&E) and CD3-stained slides. Gene expression data were generated using the NanoString nCounter assay (PanCancer Immune Profiling Panel) for 11 patients (35 samples) and analyzedusing the R package NanoStringQCPro. The scores from published immune gene signatures were calculated as a weighted sum of the expressions of their genes. All samples were analyzed for 22 immune cell subtypes relative abundance using CIBERSORT.

Results

TILs assessed on H&E and CD3-stained slides were weakly correlated (Rho= 0.38, p&lt;.001). TIL levels as well as the number of tertiary lymphoid structures (TLS) were significantly lower in Ms as compared to Ps (p&lt;.001). Among the different metastatic sites, the lung was more infiltrated when considering CD3+ and CD4+ cells (p=.01 and .02, respectively). We further observed significantly higher levels of TILs, CD3+, CD4+ and CD8+ cells in the Ms but not in the Ps from late relapsers as opposed to those from early relapsers. Gene expression analyses further confirmed these observations as several immune gene signatures displayed significantly higher scores in the Ms from late compared to early relapsers. An unsupervised analysis identified 13 genes significantly differentially expressed between Ps and Ms: CSF1R, CXCL14, CYBB, IL21R, IL2RB, TNF and TNFSF15 were upregulated in Ps while BCL2L1, C7, HSD11B1, and PSMB7 were upregulated in Ms. The matched P/M CIBERSORT analyses revealed a distinct composition of immune cell types between P and M of a same patient. Apart from a potential increase in M0 macrophages, no common trait was observed in immune cell composition between the Ms from the different patients.

Conclusion

This is to the best of our knowledge the first study characterizing the immune infiltration in patients with multiple matched P and M samples. The results suggest that Ms have not only a globally lower immune infiltration as compared to Ps, but also a different immune composition. Additionally, Ms from late relapsers are more infiltrated as compared to early relapsers. The present data also uncovers not only important inter-patient but also intra-patient immune heterogeneity, which should be taken into consideration for optimal treatment decision.

Citation Format: Szekely B, Bareche Y, Van den Eynden G, Salgado R, Buisseret L, Garaud S, Willard-Gallo K, Hatzis C, Szasz M, Kulka J, Larsimont D, Sotiriou C, Pusztai L, Desmedt C. Immune characterization of matched primary and multiple metastatic samples issued from an institutional autopsy cohort [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD5-10.

Abstract PD5-06: The immunomodulatory potential of denosumab in breast cancer: results from D-BEYOND, a window of opportunity trial evaluating a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer

Background

Breast cancer (BC) in young women has unique biology and poor prognosis. Previous reports suggest that they often express RANKL, which was also shown to play a role in mammary tumorigenesis and various immune processes. Here, we present the primary results of D-BEYOND, a window study investigating the biological activity of the RANKL inhibitor; denosumab in pre-menopausal BC patients.

Methods

D-BEYOND is a prospective, phase Iia, single-arm, multicenter study assessing the effect of denosumab on BC biology in premenopausal women with early BC (NCT01864798). Patients received two subcutaneous injections of denosumab (120mg), one week apart, followed by breast surgery. The primary endpoint was geometric mean change in tumor Ki67 assessed by immunohistochemistry (IHC). Blood, tumor and normal adjacent breast tissue were collected pre- and post-treatment. Serum levels of RANKL, OPG and CTX were assessed by ELISA. RNA was extracted from fresh-frozen tissue and RNAseq was performed. DESeq2 was used for differential expression analysis, GAGE was used for pathway analysis and CIBERSORT was used to infer immune cell subsets between pre- and post-treatment. Ki67, CD4/Foxp3 and CD4/CD8 IHC were performed on FFPE tissue to further assess the immune microenvironment. The percentage of TILs was independently evaluated by two pathologists on H&E slides. Pre- and post-treatment values were compared using a paired t-test.

Results

A total of 27 patients were enrolled in the study between October 2013 and July 2016. The median age was 45 years (range 35-51 years). Tumors of 21 patients were hormone receptor positive (77.8%), 4 were HER2 positive (14.8%) and 2 were triple negative (7.4%). No serious adverse events were reported, the most frequent non-serious adverse event being arthralgia (14.8%). After treatment, serum levels of CTX and RANKL decreased in all patients (P &lt; 0.001) whereas OPG increased in 76.9% of patients (P = 0.009, 95% CI 0.56-0.91). There was no significant reduction of Ki67 values from baseline (geometric mean [GM] change after treatment; 0.98, 95% CI 0.76-1.26; P = 0.90). Twenty-four pre- and post-treatment tumor pairs were available for RNAseq, IHC and TILs evaluation. There was a significant increase in the percentage of stromal TILs after treatment (GM change of 1.75, 95% CI 1.28–2.39; P = 0.001). 1084 differentially expressed genes were identified and pathway analysis revealed enrichment of several immune processes. CIBERSORT revealed an enrichment of CD8+ T cells (GM change 1.72, 95% CI 1.19–2.48; P = 0.006) and a decrease of Treg cells (0.71, 95% CI 0.52–0.98, P = 0.040). These results were confirmed by IHC of CD8+ and CD4+/Foxp3+ cells (GM change 1.59, 95% CI 1.14–2.21; P = 0.008 and 0.63, 95% CI 0.49–0.83, P = 0.001, respectively).

Conclusion

Short course of denosumab did not reduce tumor proliferation rate. However, it induced a significant increase in TILs and CD8 cytotoxic T cells, while Treg infiltration decreased. These findings suggest an immunomodulatory role for denosumab in young breast cancer and that its use in combination could boost immunotherapy efficacy.

Citation Format: Nguyen B, Marion M, Salgado R, Venet D, Vuylsteke P, Polastro L, Wieldiers H, Simon P, Lindeman G, Larsimont D, Van den Eynden G, Velghe C, Rothe F, Garaud S, Michiels S, Willard-Gallo K, Azim Jr HA, Loi S, Piccart M, Sotiriou C. The immunomodulatory potential of denosumab in breast cancer: results from D-BEYOND, a window of opportunity trial evaluating a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD5-06.

Abstract PD5-09: Immune parameters associated with survival in triple negative and HER2-positive breast cancer patients with 10 years of follow-up

The clinical utility of tumor-infiltrating lymphocytes (TIL) is actively being investigated in breast cancer (BC). It is unclear whether TIL spatial location and organization in tertiary lymphoid structures (TLS) have an impact on prognosis. Additionally, the significance of PD-1 and PD-L1 expression is being debated due to conflicting data from several studies. We hypothesize that the presence, extent and spatial location of multiple immune biomarkers, reflecting ongoing immune responses, will be consistently associated with a good prognosis in highly infiltrated BC [triple-negative (TNBC) and HER2+].

The relationship between these immune biomarkers and clinical outcome was examined in the TNBC and HER2+ cohorts of node-positive BC patients enrolled in the BIG 02-98 adjuvant phase III trial with available material for immunohistochemical (IHC) labeling (N=113 and N=136, respectively). HER2+ patients did not receive trastuzumab. Dual IHC staining was performed on full-face consecutive tissue sections. Scoring was independently performed by two pathologists, blinded to the clinical data, and included: global, intratumoral and stromal TIL and TLS, assessed on CD3/CD20 slides; the percentage and location of PD-1 and PD-L1 expression, assessed on PD-1/PD-L1 slides. TIL were considered as a categorical variable with different cut-offs used for each parameter and for each cohort (TNBC and HER2+). Invasive disease-free survival (I-DFS) and overall survival (OS) were analyzed (median follow-up: 10 years). Cox proportional hazard models were used for survival analyses.

The TNBC cohort revealed an association between global TIL and outcome [adjusted hazard ratio (HR) for I-DFS: 0.27 (0.15-0.51); OS: 0.26 (0.13-0.53)]. Similar results were observed for stromal and intratumoral TIL. PD-L1 expression within TLS was an independent predictor of OS, after adjustment for tumor size and age [HR: 0.30 (0.09-0.99)]. Multivariate analysis reveals this effect was principally driven by high stromal TIL (&gt;17.5% based on CD3/CD20 assessment) (χ2 OS: p=0.009). In contrast, no significant prognostic associations were found in the overall HER2+ cohort. However high T cell TIL were associated with improved I-DFS and OS in the ER-/HER2+ group [I-DFS: 0.34 (0.14-0.80); OS: 0.32 (0.12-0.86)] and stromal TIL were associated with improved I-DFS in the ER+/HER2+ group [HR: 0.29 (0.09-0.94)] (univariate analyses). No significant associations between the number of TLS nor the expression of PD-1 with outcomes were observed in either cohorts.

The presence of PD-L1+ TLS, driven by high baseline TIL, was associated with an excellent prognosis in node-positive TNBC. This observation might reflect specific immune activities taking place in these mini lymph node-like structures adjacent to the tumor bed where specific antitumor memory immune responses could be generated. No different prognostic impact was observed when analyzing TIL spatial location. Although the statistical power of the study might be limited, in line with previous findings our data reveal that, among the immune parameters evaluated, TIL are the strongest predictor of outcome in TNBC, while PD-L1+ TLS could be a new and important parameter that requires further investigation.

Citation Format: Solinas C, de Wind A, Van den Eynden G, Ameye L, Garaud S, De Silva P, Boisson A, Noel G, Langouo Fontsa M, Buisseret L, de Azambuja E, Francis PA, Di Leo A, Crown JP, Sotiriou C, Larsimont D, Paesmans M, Piccart-Gebhart M, Willard-Gallo K. Immune parameters associated with survival in triple negative and HER2-positive breast cancer patients with 10 years of follow-up [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD5-09.

Age-related changes in the BACH2 and PRDM1 genes in lymphocytes from healthy donors and chronic lymphocytic leukemia patients

Background

Age-related genetic changes in lymphocyte subsets are not currently well documented. BACH2 is a transcription factor that plays an important role in immune-mediated homeostasis by tightly regulating PRDM1 expression in both B-cells and T-cells. BACH2 gene expression is highly sensitive to DNA damage in aged mice. This concept led us to investigate the variation in BACH2 and also PRDM1 expression in major lymphocyte subsets with age.

Methods

Lymphocyte subsets from 60 healthy donors, aged from 20 to 90 years, and 41 untreated chronic lymphocytic leukemia patients were studied. BACH2 and PRDM1 gene expression was analyzed by real-time quantitative PCR. BACH2 gene expression was correlated with its protein expression. Lymphocyte apoptosis was evaluated after intracellular oxidative stress-inducing etoposide treatment of T and B cells.

Results

Our analysis shows BACH2 mRNA downregulation with age in healthy donor CD4+, CD8+ T-cells and CD19+ B-cells. Decreased BACH2 expression was also correlated with an age-related reduction in CD8 + CD28+ T-cells. We found a strong correlation between age-related BACH2 downregulation and decreased CD4+ T-cell and CD19+ B-cell apoptosis. PRDM1, as expected, was significantly upregulated in CD4+ T-cells, CD8+ T-cells and CD19+ B-cells, and inversely correlated with BACH2. A comparison of untreated chronic lymphocytic leukemia patients with age-matched healthy donors reveals that BACH2 mRNA expression was further reduced in CD4+ T-cells, CD8+ T-cells and leukemic-B cells. PRDM1 gene expression was consequently significantly upregulated in CD4+ and CD8+ T-cells in chronic lymphocytic leukemia patients but not in their leukemic B-cells.

Conclusion

Overall, our data suggest that BACH2 and PRDM1 genes are significantly correlated with age in human immune cells and may be involved in immunosenescence.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5276-2) contains supplementary material, which is available to authorized users.

FOXP1 negatively regulates tumor infiltrating lymphocyte migration in human breast cancer

Background

FOXP1, a transcriptional regulator of lymphocyte development, is abnormally expressed in some human tumors. This study investigated FOXP1-mediated regulation of tumor infiltrating lymphocytes (TIL) in untreated primary breast cancer (BC).

Methods

FOXP1 expression was analyzed in tissues from primary untreated breast tumors, BC cell lines and the METABRIC gene expression BC dataset. Cytokine and chemokine expression and lymphocyte migration in response to primary tumor supernatants (SN) was compared between FOXP1^hi and FOXP1^lo primary BC.

Finding

FOXP1 expression was higher in estrogen receptor positive compared to negative BC. FOXP1^hi tumors were significantly associated with lower TIL and fewer tertiary lymphoid structures (TLS) compared to FOXP1^lo BC. Silencing FOXP1 in BC cell lines positively impacted cytokine and chemokine expression with the inverse effect associated with overexpression. CXCL9, CXCL10, CXCL11, CXCL13, CX3CL, CCL20, IL2, IL21, GZMB and IFNG expression decreased while IL10 and TGFβ increased in FOXP1^hi compared to FOXP1^lo primary BC. Lymphocyte migration using primary BC supernatants detected decreased mobility toward FOXP1^hi supernatants. FOXP1^lo BC expresses higher levels of chemokines driving TIL migration. The METABRIC gene expression dataset analysis show FOXP1 expression is associated with unfavorable BC outcomes.

Interpretation

These data identify FOXP1 as an important negative regulator of immune responses in BC via its regulation of cytokine and chemokine expression.

Fund

Belgian Fund for Scientific Research (FNRS 3.4513.12F) and Opération Télévie (7.4636.13F and 7.4609.15F), Fonds J.C. Heuson and Fonds Lambeau-Marteaux.

Antigen Specificity and Clinical Significance of IgG and IgA Autoantibodies Produced in situ by Tumor-Infiltrating B Cells in Breast Cancer

An important role for tumor infiltrating B lymphocytes (TIL-B) in the immune response to cancer is emerging; however, very little is known about the antigen specificity of antibodies produced in situ. The presence of IgA antibodies in the tumor microenvironment has been noted although their biological functions and clinical significance are unknown. This study used a 91-antigen microarray to examine the IgG and IgA autoantibody repertoires in breast cancer (BC). Tumor and adjacent breast tissue supernatants and plasma from BC patients together with normal breast tissue supernatants and plasma from healthy controls (patients undergoing mammary reduction and healthy blood donors) were analyzed to investigate relationships between autoantibodies and the clinical, histological and immunological features of tumors. Our data show that >84% of the BC samples tested contain autoantibodies to one or more antigens on the array, with ANKRD30BL, COPS4, and CTAG1B being most frequently reactive. Ex vivo TIL-B responses were uncoupled from systemic humoral responses in the majority of cases. A comparison of autoantibody frequencies in supernatants and plasma from patients and controls identified eight antigens that elicit BC-associated autoantibody responses. The overall prevalence of IgG and IgA autoantibodies was similar and while IgG and IgA responses were not linked they did correlate with distinct clinical, pathological and immunological features. Higher levels of ex vivo IgG responses to BC-associated antigens were associated with shorter recurrence-free survival (RFS), HER2 overexpression and lower tumor-infiltrating CD8⁺ T cell counts. Higher IgA levels were associated with estrogen and progesterone receptor-negative cancers but were not significantly associated with RFS. Furthermore, ex vivo IgA but not IgG autoantibodies reactive to BC-associated antigens were linked with germinal center and early memory B cell maturation and the presence of tertiary lymphoid structures suggesting that these TIL-B are activated in the tumor microenvironment. Overall, our results extend the current understanding of the antigen specificity, the biological and the clinical significance of IgG and IgA autoantibodies produced by BC TIL-B in situ.

Abstract CT101: D-BEYOND: A window of opportunity trial evaluating denosumab, a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer

Background

Breast cancer (BC) in young women has unique biology and poor prognosis. Previous reports suggest that they often express RANKL, which was also shown to play a role in mammary tumorigenesis and the etiology of BRCA1/2 related BC. Here, we present the primary results of D-BEYOND, a window of opportunity study investigating the biological activity of the RANKL inhibitor; denosumab in pre-menopausal BC patients.

Methods

D-BEYOND is a prospective, phase IIa, single-arm, multicenter study assessing the effect of denosumab on BC biology in premenopausal women with early BC (NCT01864798). Patients received two subcutaneous injections of denosumab (120mg), one week apart, followed by breast surgery. Blood, tumor and normal adjacent breast tissue were collected at baseline and at surgery. The primary endpoint was geometric mean change in tumor Ki67 assessed by immunohistochemistry (IHC) from baseline to surgery. Absolute Ki67 responders were defined as having &lt;2.7% IHC staining in the post-treatment tumor. Serum levels of soluble RANKL (sRANKL), OPG and C-terminal telopeptide (CTX) were assessed by ELISA. Ki67, RANK and RANKL expression were assessed by IHC. The percentage of tumor infiltrating lymphocytes (TILs) were also evaluated. Pre- and post-treatment values were compared using a paired t-test.

Results

A total of 27 patients were enrolled in the study between October 2013 and July 2016. The median age was 45 years (range 35-51 years). Tumors of 21 patients were hormone receptor positive (77.8%), 4 were HER2 positive (14.8%) and 2 were triple negative (7.4%). No serious adverse events were reported, the most frequent non-serious adverse event being arthralgia (14.8%). After treatment, serum levels of CTX and sRANKL decreased in all patients (P &lt; 0.001) whereas serum levels of OPG increased in 76.9% of patients (P = 0.009, 95% CI 0.56-0.91). There was no significant reduction of Ki67 values from baseline (geometric mean change after treatment; 0.98, 95% CI 0.76-1.26; P = 0.90) and there were no absolute Ki67 responders. Twenty-four pre- and post-treatment tumor pairs were available for RANK/L staining and TILs assessment. There was no significant difference in RANKL and RANK H-score in tumors after treatment (P = 0.842, P = 0.142, respectively) but we observed a decrease of RANKL H-score in 3 tumors (12.5%) and an increase of RANK H-score in 5 tumors (20%). Interestingly, there was a significant increase in the percentage of stromal TILs after treatment (geometric mean change of 2.51, 95% CI 1.58-3.97; P = 0.004). There were 10/24 patients (41.7%) with a change in TILs of at least 10%, all of them having an increase in TILs presence (P = 0.002).

Conclusion

Short course of denosumab did not reduce tumor proliferation rate. However, it induced a significant increase in TILs. These findings suggest that denosumab may potentiate immunotherapy efficacy, at least in young BC patients. Additional results including immune cell profiling by multiplex IHC and RNA-sequencing of tumor and normal tissues will be presented at the meeting.

Citation Format: Bastien Nguyen, Marion Maetens, Roberto Salgado, David Venet, Peter Vuylsteke, Laura Polastro, Hans Wieldiers, Philippe Simon, Geoff Lindeman, Denis Larsimont, Gert Van den Eynden, Chloe Velghe, Francoise Rothe, Soizic Garaud, Stefan Michiels, Karen Willard-gallo, Hatem A. Azim, Sherene Loi, Martine Piccart, Christos Sotiriou. D-BEYOND: A window of opportunity trial evaluating denosumab, a RANK-ligand (RANKL) inhibitor and its biological effects in young pre-menopausal women diagnosed with early breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT101.

Abstract 4689: Immune functions and regulation of follicular helper CD4+CXCR5+T cells in human breast cancer

Introduction: High levels of tumor infiltrating lymphocytes (TIL) have been associated with good clinical outcomes in patients with HER2-positive (HER2+) and triple-negative (TN) breast cancer (BC) . Recently, we demonstrated that 60% of BC TIL are organized in tertiary lymphoid structures (TLS) located in the stroma. We further identified a CXCL13-producing CD4+ T follicular helper cell (Tfh) subpopulation and demonstrated that this chemokine, important for TLS formation, is associated with positive clinical outcomes in BC. The aim of the present study was to investigate how conventional CD4+ Tfh cells, expressing the CXCL13 receptor CXCR5, contribute to immune function and regulation in BC-associated TLS.

Methods: We prospectively collected fresh primary BC tissues and prepared enzyme-free homogenates to prepare tumor supernatant and TIL for flow cytometric analysis and sorting. Matching formalin-fixed paraffin-embedded (FFPE) were used for subsequent spatial analysis by dual IHC and confocal microscopy.

Results: Flow cytometric analyses show that ~15% CD4+, ~13% CD8+ and &gt;95% B cell TIL express CXCR5 while confocal microscopy reveals that these CXCR5+ TIL subpopulations co-localize in BC TLS and their presence is tightly correlated. BC Tfh TIL (compared to activated tonsillar Tfh) have a memory phenotype and express ICOS and PD-1 suggesting they are activated, but BCL6 is undetectable and CXCL13 positive cells are rare in only some tumors. RNA analysis detected high expression of IL-21, IL-10 and CXCL13 in Tfh TIL. Investigation into the role of Tfh cells in TLS functionality was accomplished via an in vitro assay where Tfh TIL were activated with allogeneic splenic B cells. These experiments reveal that only ICOS+PD-1+Tfh TIL from TN/HER2+ BC are capable of inducing IgM and IgG secretion by B cells. A comparison of ICOS+PD-1+ with ICOS-PD-1- Tfh TIL confirms an activated, functional nature for the former characterized by high levels of IL-21, IL-10 and CXCL13 mRNA expression. We also found specialized follicular regulatory T cells (Tfr), expressing CXCR5, CD25, demethylated Foxp3 and GARP, localized in TLS. To understand the regulation of Tfh function(s) by Tfr we quantified immunoglobulins in the primary tumor supernatant, finding a correlation between the Tfh/Tfr ratio (fresh tissues) and IgG and IgM production (supernatant) in TN/HER2+ BC. These data suggest that the balance between effector and regulatory Tfh influences B cell differentiation in TLS.

Conclusions: We show that it is possible to isolate functional Tfh TIL from fresh BC tissues, demonstrate their activation and functional state and link a Tfr presence with negative regulation of TLS function. These data begin to shed light on anti-tumor immune responses occurring in TLS at the tumor site, whose functional activities may have important treatment implications, particularly for immunotherapy in BC.

Citation Format: Mireille Langouo, Gregory Noël, Gert Van den Eynden, Alexandre De Wind, Soizic Garaud, Pushpamali De Silva, Cinzia Solinas, Anais Boisson, Celine Naveaux, Hugues Duvillier, Ligia Craciun, Denis Larsimont, Martine Piccart-Gebhart, Karen Willard-Gallo. Immune functions and regulation of follicular helper CD4+CXCR5+T cells in human breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4689.

Abstract 1624: Reliability of immune biomarker assessment in breast cancer: A report on interobserver variability from studies at a single institution

Reproducible evaluation of immune infiltration parameters is needed for the development of reliable biomarkers in the era of cancer immunotherapy. This study investigated inter-observer reproducibility when evaluating tumor-infiltrating lymphocytes (TIL), tertiary lymphoid structures (TLS), PD-1 and PD-L1 positivity on immunohistochemically-stained (IHC) breast cancer (BC) tissues, including detailed analysis of spatial positioning in the tumor microenvironment and expression on individual positive cells. Retrospectively collected archival BC samples (N=441) were dual IHC-stained for CD3 (pan T cells) plus CD20 (pan B cells) for TIL and TLS assessment with a consecutive tissue section dual-IHC stained for PD-1 and PD-L1. The 882 tissue sections were independently read by two immuno-pathologists blinded to the clinical data for specific studies between 2014 and 2017. Five independent study series were used for the current analysis: 1) samples of BC relapses, 2) residual disease in breast after neodjuvant treatment, and 3) three independent series of untreated primary tumors. Intraclass correlation coefficients for evaluations are shown in the table below:

RelapsesResidual diseaseUntreated primary tumorsSeries 1: N=88Series 2: N=20Series 3: N=85Series 4: N=113Series 5: N=135201420142014-201520162017ICCICCICCICCICC%Stromal TIL0.85 [0.76-0.90]0.71 [0.27-0.89]0.79 [0.68-0.87]0.74 [0.62-0.82]0.77 [0.68-0.83]%Intratumoral TIL0.40 [0.09-0.61]0.63 [0.08-0.86]0.73 [0.58-0.82]0.87 [0.81-0.91]0.64 [0.51-0.74]%Global TIL0.87 [0.80-0.92]0.79 [0.47-0.92]0.83 [0.74-0.89]0.80 [0.72-0.86]0.81 [0.73-0.86]%CD30.83 [0.74-0.89]0.71 [0.28-0.89]0.81 [0.70-0.88]0.72 [0.60-0.80]0.73 [0.63-0.81]%CD200.74 [0.62-0.81]0.81 [0.52-0.92]0.76 [0.63-0.84]0.78 [0.68-0.84]0.78 [0.70-0.84]TLS0.80 [0.70-0.87]0.78 [0.45-0.91]0.83 [0.74-0.89]0.95 [0.93-0.97]0.97 [0.96-0.98]%PD-L1 tumor cells0.78 [0.66-0.86]0.56 [-0.12-0.82]0.82 [0.73-0.89]0.62 [0.45-0.74]0.45 [0.25-0.61]%PD-L1 stromal cells0.61 [0.40-0.74]-1.56 [-1.53-0.60]0.43 [0.12-0.63]0.61 [0.44-0.73]0.31 [0.05-0.5]%PD-L1 immune cells0.53 [0.29-0.70]0.94 [0.84-0.97]0.29 [-0.09-0.54]0.38 [0.10-0.57]0.10 [-0.25-0.35]%PD-1 TLS-0.00 [-0.54-0.35]NA0.72 [0.57-0.82]0.57 [0.35-0.72]0.76 [0.62-0.84]

Cohen's κ coefficients reveal poor agreement (κ&lt;0.4) for assessment of the categorical global PD-1 and PD-L1 variables (cut-off &gt;1%). Sporadically, fair agreement (κ&gt;0.4) was observed for PD-L1 expressed by immune and tumor cells. Globally, the inter-observer agreement remained constant overtime. Poor reproducibility for categorical global PD-1 and global PD-L1 assessment was observed. On the contrary, pathologists have excellent reproducibility for assessing global TIL and TLS, good/excellent reproducibility for PD-1 in TLS (primary tumors) and for PD-L1 expression on tumor cells which make these of great interest for clinical use.

Citation Format: Cinzia Solinas, Gert Van den Eynden, Alexandre De Wind, François Richard, Anaïs Boisson, Soizic Garaud, Karen Willard-Gallo. Reliability of immune biomarker assessment in breast cancer: A report on interobserver variability from studies at a single institution [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1624.

Immunity drives TET1 regulation in cancer through NF-κB

Ten-eleven translocation enzymes (TET1, TET2, and TET3), which induce DNA demethylation and gene regulation by converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), are often down-regulated in cancer. We uncover, in basal-like breast cancer (BLBC), genome-wide 5hmC changes related to TET1 regulation. We further demonstrate that TET1 repression is associated with high expression of immune markers and high infiltration by immune cells. We identify in BLBC tissues an anticorrelation between TET1 expression and the major immunoregulator family nuclear factor κB (NF-κB). In vitro and in mice, TET1 is down-regulated in breast cancer cells upon NF-κB activation through binding of p65 to its consensus sequence in the TET1 promoter. We lastly show that these findings extend to other cancer types, including melanoma, lung, and thyroid cancers. Together, our data suggest a novel mode of regulation for TET1 in cancer and highlight a new paradigm in which the immune system can influence cancer cell epigenetics.

Abstract PD6-07: Clinical significance of CD73 expression in triple-negative breast cancer from the BIG 02-98 adjuvant phase III clinical trial

Background: CD73 is an ecto-enzyme that promotes tumor immune escape through the production of immunosuppressive extracellular adenosine in the tumor microenvironment. Several CD73 inhibitors and adenosine receptor antagonists are being evaluated in phase I clinical trials.

Objective: To investigate the prognosis significance of CD73 in human triple-negative breast cancer.

Design and setting: This is a prospective-retrospective biomarker analysis. Using multiplex immunofluorescence and image analysis, we assessed CD73 protein expression on tumor cells, tumor-infiltrating leukocytes and stromal cells on full-face sections from formalin-fixed paraffin-embedded primary breast tumors.

Participants: 122 samples of triple-negative breast cancer from the BIG 02-98 adjuvant phase III clinical trial were included in our analysis. This trial compared the addition of taxanes to anthracyclines-based chemotherapy in node-positive breast cancer.

Results: Our results demonstrated that high levels of CD73 expression on epithelial tumor cells were significantly associated with reduced disease-free survival (DFS) and overall survival (OS) in patients with triple-negative breast cancer. Using the median as a threshold between low and high levels of CD73 on epithelial cells, hazard ratios (HR) adjusted for grade, number of positive lymph nodes and tumor size, were of 2.21 (95% confidence interval (CI): 1.15-4.25); p=0.02 for DFS and of 2.47 (95%CI: 1.21-5.07); p=0.01 for OS. CD73 expression negatively correlated with tumor immune infiltration (Spearman's R= -0.50, p&lt;0.0001). Patients with high levels of CD73 and low levels of tumor-infiltrating leukocytes had the worse clinical outcome (HR: 4.24 (1.90-9.45), p&lt;0.001 for DFS, HR: 3.91 (1.65-9.31), p=0.002 for OS) compared to patients with low CD73 and high tumor-immune infiltration. Flow cytometric analysis of tumor-infiltrating leukocytes revealed a high frequency of CD73-expressing B cells and higher CD73 expression on tumor-infiltrating myeloid cells and natural killer cells compared to peripheral blood.

Conclusion and relevance: Taken together, our study provides further support that CD73 expression is associated with a poor prognosis and reduced anti-tumor immunity in human triple-negative breast cancer and that targeting CD73 could be a promising strategy to reprogram the tumor microenvironment in this breast cancer subtype.

Citation Format: Buisseret L, Pommey S, Allard B, Garaud S, Bergeron MA, Cousineau I, Ameye L, Paesmans M, Crown JPA, Di Leo A, Piccart-Gebhart M, Willard-Gallo K, Sotiriou C, Stagg J. Clinical significance of CD73 expression in triple-negative breast cancer from the BIG 02-98 adjuvant phase III clinical trial [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD6-07.

Immuno-oncology-101: overview of major concepts and translational perspectives

Cancer immunotherapy is demonstrating impressive clinical benefit in different malignancies and clinical oncologists are increasingly turning their attention to immune-oncology. It is now well recognized that innate and adaptive immune cells infiltrating tumors are associated with clinical outcomes and responses to treatments, and can be harnessed to patients' benefit. Considerable advances have also been made in understanding how cancers escape from immune attack. Targeting of immunological escape processes regulated by the expression of immune checkpoint receptors and ligands and the down-modulation of tumor antigen presentation is the basis of immuno-oncology treatments. Despite recent achievements, there remain a number of unresolved issues in order to successfully implement cancer immunotherapy in many cancers. Importantly, clinical biomarkers are still needed for better optimization of emerging combination immunotherapies and better treatment tailoring. In this review, we summarize the function of innate and adaptive immune cells in anti-tumor immunity and the general mechanisms exploited by tumor cells to escape and inhibit immune responses as well as therapeutic strategies developed to overcome these mechanisms and discuss emerging biomarkers in immuno-oncology.

Quantifying Tertiary Lymphoid Structure-Associated Genes in Formalin-Fixed Paraffin-Embedded Breast Cancer Tissues

Tertiary lymphoid structures (TLS) have been detected in several types of human solid tumors. These structures are thought to regulate local adaptive immune responses that can promote or antagonize tumor progression. Despite positive prognostic values associated with a TLS presence in several studies, discrepancies still exist. TLS are structurally organized entities composed of varying numbers of multiple cell types making their assessment in tumor tissues, particularly biopsies, challenging. Immunohistochemical staining of TLS-related cell populations is the most frequently used method for identifying and scoring them; however, TLS-related gene expression has also been explored. The protocols described are detailed to allow the user to quantify TLS-related gene expression on formalin-fixed paraffin-embedded human breast tumor tissues.

Immune Checkpoint Molecules on Tumor-Infiltrating Lymphocytes and Their Association with Tertiary Lymphoid Structures in Human Breast Cancer

There is an exponentially growing interest in targeting immune checkpoint molecules in breast cancer (BC), particularly in the triple-negative subtype where unmet treatment needs remain. This study was designed to analyze the expression, localization, and prognostic role of PD-1, PD-L1, PD-L2, CTLA-4, LAG3, and TIM3 in primary BC. Gene expression analysis using the METABRIC microarray dataset found that all six immune checkpoint molecules are highly expressed in basal-like and HER2-enriched compared to the other BC molecular subtypes. Flow cytometric analysis of fresh tissue homogenates from untreated primary tumors show that PD-1 is principally expressed on CD4⁺ or CD8⁺ T cells and CTLA-4 is expressed on CD4⁺ T cells. The global proportion of PD-L1⁺, PD-L2⁺, LAG3⁺, and TIM3⁺ tumor-infiltrating lymphocytes (TIL) was low and detectable in only a small number of tumors. Immunohistochemically staining fixed tissues from the same tumors was employed to score TIL and tertiary lymphoid structures (TLS). PD-L1⁺, PD-L2⁺, LAG3⁺, and TIM3⁺ cells were detected in some TLS in a pattern that resembles secondary lymphoid organs. This observation suggests that TLS are important sites of immune activation and regulation, particularly in tumors with extensive baseline immune infiltration. Significantly improved overall survival was correlated with PD-1 expression in the HER2-enriched and PD-L1 or CTLA-4 expression in basal-like BC. PD-1 and CTLA-4 proteins were most frequently detected on TIL, which supports the correlations observed between their gene expression and improved long-term outcome in basal-like and HER2-enriched BC. PD-L1 expression by tumor or immune cells is uncommon in BC. Overall, the data presented here distinguish PD-1 as a marker of T cell activity in both the T and B cell areas of BC associated TLS. We found that immune checkpoint molecule expression parallels the extent of TIL and TLS, although there is a noteworthy amount of heterogeneity between tumors even within the same molecular subtype. These data indicate that assessing the levels of immune checkpoint molecule expression in an individual patient has important implications for the success of therapeutically targeting them in BC.

Reliability of tumor-infiltrating lymphocyte and tertiary lymphoid structure assessment in human breast cancer

The presence of tumor-infiltrating lymphocytes (TIL), reflecting host immune activity, is frequently correlated with better clinical outcomes, particularly in HER2-positive and triple-negative breast cancer. Recent findings suggest that organization of immune infiltrates in tertiary lymphoid structures also has a beneficial effect on survival. This study investigated inter- and intra-observer variation in TIL assessment using conventional hematoxylin-eosin versus immunohistochemical staining to identify immune cells. Global, intratumoral, and stromal TIL, as well as tertiary lymphoid structures were scored independently by experienced pathologists on full-face tumor sections (n=124). The fidelity of scoring infiltrates in core biopsies compared to surgical specimens, and pathological assessment compared to quantitative digital analysis was also evaluated. The inter-observer concordance correlation coefficient was 0.80 for global, 0.72 for intratumoral, and 0.71 for stromal TIL, while the intra-observer concordance correlation coefficient was 0.90 for global, 0.77 for intratumoral, and 0.89 for stromal TIL using immunohistochemical stains. Correlations were lower with hematoxylin-eosin stains, particularly for intratumoral TIL, while global scores had the highest concordance correlation coefficients. Our study concluded that tertiary lymphoid structures are accurately and consistently scored using immunohistochemical but not hematoxylin-eosin stains. A strong association was observed between TIL in core biopsies and surgical samples (R²=0.74) but this did not extend to tertiary lymphoid structures (R²=0.26). TIL scored by pathologists and digital analysis were correlated but our analysis reveals a constant bias between these methods. These data challenge current criteria for TIL and tertiary lymphoid structure assessment in breast cancer and recommend that how pathologists evaluate immune infiltrates be reexamined for future studies.

DNA methylation-based immune response signature improves patient diagnosis in multiple cancers

BACKGROUND

The tumor immune response is increasingly associated with better clinical outcomes in breast and other cancers. However, the evaluation of tumor-infiltrating lymphocytes (TILs) relies on histopathological measurements with limited accuracy and reproducibility. Here, we profiled DNA methylation markers to identify a methylation of TIL (MeTIL) signature that recapitulates TIL evaluations and their prognostic value for long-term outcomes in breast cancer (BC).

METHODS

MeTIL signature scores were correlated with clinical endpoints reflecting overall or disease-free survival and a pathologic complete response to preoperative anthracycline therapy in 3 BC cohorts from the Jules Bordet Institute in Brussels and in other cancer types from The Cancer Genome Atlas.

RESULTS

The MeTIL signature measured TIL distributions in a sensitive manner and predicted survival and response to chemotherapy in BC better than did histopathological assessment of TILs or gene expression-based immune markers, respectively. The MeTIL signature also improved the prediction of survival in other malignancies, including melanoma and lung cancer. Furthermore, the MeTIL signature predicted differences in survival for malignancies in which TILs were not known to have a prognostic value. Finally, we showed that MeTIL markers can be determined by bisulfite pyrosequencing of small amounts of DNA from formalin-fixed, paraffin-embedded tumor tissue, supporting clinical applications for this methodology.

CONCLUSIONS

This study highlights the power of DNA methylation to evaluate tumor immune responses and the potential of this approach to improve the diagnosis and treatment of breast and other cancers.

FUNDING

This work was funded by the Fonds National de la Recherche Scientifique (FNRS) and Télévie, the INNOVIRIS Brussels Region BRUBREAST Project, the IUAP P7/03 program, the Belgian "Foundation against Cancer," the Breast Cancer Research Foundation (BCRF), and the Fonds Gaston Ithier.

Abstract 3694: FOXP1 suppresses immune cell migration in breast tumors

Tumor infiltrating lymphocytes (TIL) play an essential role in mediating response to chemotherapy and improving clinical outcomes in breast cancer (BC). Extensive TIL infiltration is characterized by their organized into tertiary lymphoid structures (TLS). TIL infiltration and TLS formation may be regulated, in part, by transcription factors (TF) controlling cytokine/chemokine production within the tumor microenvironment. The forkhead box protein 1 (FOXP1) is a TF shown to be abnormally expressed in a variety of human tumors and play an important role in T cell cytokine production. Therefore we aimed to study FOXP1-mediated regulation of TIL in BC. Investigation of FOXP1 expression in public microarray data from untreated BC patients, BC cell lines [Luminal A (MCF7), HER2+ (BT474) and triple negative (TN; MDA-MB231)] and prospectively collected formalin-fixed paraffin-embedded (FFPE) primary breast tissues showed that FOXP1 is repressed at transcript and protein level in HER2+ or TN breast tumors compared to estrogen receptor positive tumors (Luminal A and B). Moreover HER2+ and TN subtypes, which showed decreased FOXP1 levels, are 2 well known highly infiltrated BC. Based on our hypothesis that FOXP1 could play a role on immune cell infiltration in breast tumors, data analysis of the prospective BC cohort showed that high FOXP1 (FOXP1hi) expression is significantly associated with a lower percentage of TIL and number of TLS compared to FOXP1 low (FOXP1lo) tumors. To investigate the impact on specific cytokines/chemokines involved in TIL recruitment and/or TLS formation, FOXP1 was silenced in MCF7 (FOXP1hi tumor cell line) or upregulated in MDA-MB-231 (FOXP1lo tumor cell line) followed by gene expression analysis using a RT-qPCR based human cytokine/chemokine array. FOXP1 repression upregulated major T and B cell chemoattractant chemokines and overexpression repressed most of these molecules in the cell line experiments. Next we analyzed major chemoattractant molecule expression in FOXP1lo and FOXP1hi prospective breast tumors and found that FOXP1hi tumors having a significant decrease in CXCL9, CXCL10, CXCL11, CXCL13, CX3CL, CCL20, IL2, and IL21. A migration assay (Transwell chambers) done using healthy donor (HD) PBMC showed a significant increase in total lymphocytes migrated towards FOXP1 repressed tumor conditioned media (TCM) of MCF7 compared to the TCM of control or medium alone. Finally analysis of lymphocyte migration to FOXP1lo and FOXP1hi tumor supernatants (SN) from primary tumors that we consistently prepare without enzymatic digestion, showed that there was a significant decrease in number of lymphocytes migrated towards FOXP1hi tumor SN including the migration rates of individual T and B lymphocytes populations compared to FOXP1lo tumor SN. These data suggest that FOXP1 could play a critical role in establishing effective anti-tumor immune responses by negative regulation of TIL via suppression of cytokine/chemokine expression in breast tumors.

Citation Format: Pushpamali De Silva, Soizic Garaud, Roland de Wind, Gert Van den Eynden, Anaïs Boisson, Cinzia Solinas, Edoardo Migliori, Hugues Duvillier, Denis Larsimont, Martine Piccart-Gebhart, Karen Willard-Gallo. FOXP1 suppresses immune cell migration in breast tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3694. doi:10.1158/1538-7445.AM2017-3694

CXCL13-producing TFH cells link immune suppression and adaptive memory in human breast cancer

T follicular helper cells (TFH cells) are important regulators of antigen-specific B cell responses. The B cell chemoattractant CXCL13 has recently been linked with TFH cell infiltration and improved survival in human cancer. Although human TFH cells can produce CXCL13, their immune functions are currently unknown. This study presents data from human breast cancer, advocating a role for tumor-infiltrating CXCL13-producing (CXCR5-) TFH cells, here named TFHX13 cells, in promoting local memory B cell differentiation. TFHX13 cells potentially trigger tertiary lymphoid structure formation and thereby generate germinal center B cell responses at the tumor site. Follicular DCs are not potent CXCL13 producers in breast tumor tissues. We used the TFH cell markers PD-1 and ICOS to identify distinct effector and regulatory CD4+ T cell subpopulations in breast tumors. TFHX13 cells are an important component of the PD-1hiICOSint effector subpopulation and coexpanded with PD-1intICOShiFOXP3hi Tregs. IL2 deprivation induces CXCL13 expression in vitro with a synergistic effect from TGFβ1, providing insight into TFHX13 cell differentiation in response to Treg accumulation, similar to conventional TFH cell responses. Our data suggest that human TFHX13 cell differentiation may be a key factor in converting Treg-mediated immune suppression to de novo activation of adaptive antitumor humoral responses in the chronic inflammatory breast cancer microenvironment.

Abstract A62: Investigating the role of follicular helper T cells, B cells and CXCL13 in breast cancer-associated tertiary lymphoid structures

Patient outcomes have been linked to the presence of tumor infiltrating lymphocytes (TIL) in solid tumors. In human breast cancer (BC), higher TIL infiltration is associated with a better prognosis and also predicts relevant responses to pre-operative chemotherapy. TIL are primarily composed of T cells, albeit around 20% of BC patients show significant B cell infiltration, and can organize in tertiary lymphoid structures (TLS) located in the peritumoral stroma 1, which are associated with survival in HER2+ and triple negative BC patients. Further, these studies revealed that CD4+ follicular helper T (Tfh) cells producing CXCL13 were specifically associated with peritumoral TLS. CXCL13 is an important B cell chemoattractant whose function is to recruit B cells to the germinal center (GC) in secondary lymphoid organs and TLS, where they can mature and differentiate into memory or antibody-producing B cells. Our recent efforts have focused on exploring the role of Tfh, B cells and CXCL13 play in the development and/or maintenance of GC-like structures in BC-associated TLS. We first derived a GC-B cell gene signature for integration in our published Tfh cell gene signature 1. The combined gene signature was tested for its ability to sensitively detect BC-associated TLS using a qRT-PCR-based assay and a retrospective series (n=54) of formalin-fixed paraffin-embedded (FFPE) BC tissues. These data revealed a correlation between gene signature expression and the extent of TIL and TLS scored by trained pathologists on dual-immunohistochemistry stained (CD3+CD20 for T and B cells, respectively) FFPE tissue sections. The detection of TLS using our combined GC-B cell/Tfh cell gene signature was subsequently confirmed using tissues from our prospective BC cohort (n=83). In addition, CXCL13 gene expression was well correlated with genes associated with GC-B cells and Tfh, indicating these parameters are closely related, as confirmed by immunofluorescence staining on FFPE tissues.

Further understanding the factors that promote TLS formation in vivo could provide important insight for treatment decisions in BC. CXCL13 expression was originally identified as an important signal associated with TLS that was predictive for patient outcomes 1. Factors capable of inducing CXCL13 expression in CD4+ T cells isolated from peripheral blood were investigated using flow cytometry. TGFβ1 alone or together with several cytokines (IL4, IL12, IL21, IL23 and in particular IL2 blockade) increased CXCL13 expression in activated CD4+ T cells. Similar to our characterization of Tfh TIL in fresh tumor tissues, these CXCL13-producing CD4+ T cells were CXCR5 negative and expressed the Tfh marker ICOS; however, they only had low levels of PD-1 expression compared to PD-1hi Tfh cells. CD8+ T cells were also found to produce CXCL13 albeit at low levels. The currently ongoing identification of critical genes involved in regulating CXCL13 production in treated CD4+T cells will help to elucidate the mechanism(s) underlying chemokine induction. The increased accuracy in TIL and TLS detection in BC together with a better understanding of the role Tfh and CXCL13 play in these structures (and GC) development should help to identify the critical immune components involved in BC TLS formation.

1Gu-Trantien et al. J Clin Invest. 2013

Citation Format: Edoardo Migliori, Chunyan Gu-Trantien, Soizic Garaud, Gert Van den Eynden, Alexandre De Wind, Pushpamali De Silva, Cinzia Solinas, Anais Boisson, Celine Naveaux, Denis Larsimont, Martine Piccart-Gebhart, Karen Willard-Gallo. Investigating the role of follicular helper T cells, B cells and CXCL13 in breast cancer-associated tertiary lymphoid structures. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr A62.

Abstract P2-04-04: BRCA gene mutations do not shape the extent and organization of tumor infiltrating lymphocytes in triple negative breast cancer

The remarkable responses observed in metastatic cancer patients treated with immunotherapies, including inhibitors directed to the PD-1 and PD-L1 checkpoint molecules, makes it a priority to identify critical variations in pro- and anti-tumor immune responses in breast cancer (BC). In patients with triple negative (TN) BC, an increased presence of tumor infiltrating lymphocytes (TIL) and tertiary lymphoid structures (TLS) have been associated with good clinical outcomes. However, the frequency of specific lymphocyte subpopulations, PD-1 and/or PD-L1 expression and their prognostic significance remains an open question. Our recent work found that PD-1 and PD-L1 expression are specifically associated with higher TIL densities and an increased number of TLS in BC. We further demonstrated that TIL density, TLS and PD-L1 expression were correlated with more aggressive breast tumor characteristics, including higher proliferation and hormone receptor negativity. In this project, we examined the prevalence of TIL, TLS, PD-1 and PD-L1 expression in TNBC and further compared these immune parameters between TNBC patients harboring BRCA1 or BRCA2 germline gene mutations with those carrying the wild-type (wt) genes.

A total of 1402 BC patients whose blood was genetically tested for germline BRCA1 and BRCA2 mutations were examined for inclusion in this study. Ninety-eight chemotherapy-naïve patients with primary invasive ER–, PR– and HER2– BC and demonstrated germline BRCA1 or BRCA2 wt or mutated-gene status were included in this study. Ninety-four tumors were determined to be suitable for evaluating immune cell infiltration (51 BRCA wt and 43 BRCA-mutated). FFPE tumor tissue from the surgical specimens was analyzed by immunohistochemistry (IHC) staining of full-face tissue sections. IHC was performed as a dual label using CD3 plus CD20 for T and B cells, CD4 plus CD8 for the major T cell subpopulations and PD-1 plus PD-L1 for individual or paired expression of these receptors. The stained slides were independently scored by two experienced pathologists for TIL, TIL subpopulations, TLS and checkpoint molecule expression.

These analyses revealed that 87% of our TNBC cohort was TIL-positive (≥10% TIL) with 35% classified as lymphocyte predominant BC (LPBC; ≥50% TIL). T cells were the principal component of the lymphocytic infiltrate with no significant differences between the BRCA wt and BRCA-mutated groups detected in total T cells (CD3+), helper T cells (CD4+), cytotoxic T cells (CD8+) or B cells (CD20+). TLS were identified in 73% of tumors with again no significant differences between the BRCA groups. Examination of checkpoint molecule expression identified 33% tumors as PD-1 positive and 40% as PD-L1 positive. PD-1 expression was correlated with PD-L1 expression and both with TIL positivity and the level of immune infiltration but not BRCA mutational status.

Overall, our analyses revealed that BRCA wt and BRCA-mutated TNBC are remarkably similar in terms of TIL heterogeneity, a TLS presence and checkpoint molecule expression. These data suggest that BRCA gene mutations are not immunogenic nor do they directly drive immune infiltration in TNBC.

Citation Format: Willard-Gallo K, Solinas C, Marcoux D, t'Kint de Roodenbeke D, Garaud S, Van den Eynden G, de Wind A, Boisson A, Larsimont D, Piccart M. BRCA gene mutations do not shape the extent and organization of tumor infiltrating lymphocytes in triple negative breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-04.