Immunodynamics of explanted human tumors for immuno-oncology

Decision making in immuno‐oncology is pivotal to adapt therapy to the tumor microenvironment (TME) of the patient among the numerous options of monoclonal antibodies or small molecules. Predicting the best combinatorial regimen remains an unmet medical need. Here, we report a multiplex functional and dynamic immuno‐assay based on the capacity of the TME to respond to ex vivo stimulation with twelve immunomodulators including immune checkpoint inhibitors (ICI) in 43 human primary tumors. This "in sitro" (in situ/in vitro) assay has the potential to predict unresponsiveness to anti‐PD‐1 mAbs, and to detect the most appropriate and personalized combinatorial regimen. Prospective clinical trials are awaited to validate this in sitro assay.

Resolving the Paradox of Colon Cancer Through the Integration of Genetics, Immunology, and the Microbiota

While colorectal cancers (CRC) are paradigmatic tumors invaded by effector memory lymphocytes, the mechanisms accounting for the relative resistance of MSI negative CRC to immunogenic cell death mediated by oxaliplatin and immune checkpoint inhibitors has remained an open conundrum. Here, we propose the viewpoint where its microenvironmental contexture could be explained -at least in part- by macroenvironmental cues constituted by the complex interplay between the epithelial barrier, its microbial ecosystem, and the local immune system. Taken together this dynamic ménage-à-trois offers novel coordinated actors of the humoral and cellular immune responses actionable to restore sensitivity to immune checkpoint inhibition. Solving this paradox involves breaking tolerance to crypt stem cells by inducing the immunogenic apoptosis of ileal cells in the context of an ileal microbiome shifted towards immunogenic bacteria using cytotoxicants. This manoeuver results in the elicitation of a productive Tfh and B cell dialogue in mesenteric lymph nodes culminating in tumor-specific memory CD8+ T cell responses sparing the normal epithelium.

Elucidating the gut microbiota composition and the bioactivity of immunostimulatory commensals for the optimization of immune checkpoint inhibitors

Accumulating evidence from preclinical studies and human trials demonstrated the crucial role of the gut microbiota in determining the effectiveness of anticancer therapeutics such as immunogenic chemotherapy or immune checkpoint blockade. In summary, it appears that a diverse intestinal microbiota supports therapeutic anticancer responses, while a dysbiotic microbiota composition that lacks immunostimulatory bacteria or contains overabundant immunosuppressive species causes treatment failure. In this review, we explore preclinical and translational studies highlighting how eubiotic and dysbiotic microbiota composition can affect progression-free survival in cancer patients.

Abstract 1970: Inhibition of BRAF-V600E increases melanocyte antigen expression and antigen-specific recognition in melanoma without altering T cell function

Given the high prevalence of BRAFV600E mutations in melanoma, targeted therapy against BRAF, or its mutated form, is a promising new therapeutic approach for patients with melanoma. Preliminary evidence suggests that BRAFV600E contributes to immune escape, and that blocking its activity via MAPK pathway inhibition leads to increased expression of melanocyte differentiation antigens, supporting the potential use of combination targeted therapy and immunotherapy. However, indiscriminate MAPK pathway inhibition may have deleterious effects on the immune system and lead to T cell dysfunction.

The purpose of these studies was to explore the role of oncogenic BRAF in immune evasion by melanoma cells through its suppression of melanocyte differentiation antigens (MDAs). Furthermore, we sought to evaluate the effect of MAPK pathway inhibition on T lymphocyte function as a basis for combined targeted therapy and immunotherapy.

Melanoma cell lines were cultured with MEK inhibitors (U0126, PD0325901) or a specific inhibitor of BRAFV600E (PLX4720) and expression of MDAs was assayed at the mRNA and protein level. The level of micro-opthalmia transcription factor (MITF), a transcriptional regulator of MDAs, was also assayed. Untreated and treated melanoma cell lines were co-cultured with antigen-specific T lymphocytes (generated by transduction of lymphocytes with MART-1- and gp100-specific T cell receptors) and reactivity was measured via interferon gamma release. The effect of MAPK pathway inhibition on T lymphocyte function was analyzed by assaying fold-expansion after OKT-3 & IL-2 stimulation as well as antigen-specific interferon gamma release.

Inhibition of MAPK pathway in melanoma cell lines resulted in increased levels of MDAs which was associated with improved antigen-specific recognition by MART-1- and gp100-specific T lymphocytes. This was associated with higher intracellular levels of MITF. Treatment with MEK inhibitors resulted in impaired T lymphocyte function, as assayed by T cell expansion and antigen-specific interferon gamma release, whereas T cell function was preserved after treatment with a specific inhibitor of BRAFV600E.

These findings suggest that oncogenic BRAF contributes to immune evasion by transcriptional repression of melanocyte antigen expression through MITF, which may be reversed by targeted MAPK pathway inhibition. Selective inhibition of BRAFV600E enhances MDA expression while preserving T cell function, whereas MEK inhibition has deleterious effects on T cell function. These data have important implications for the design of clinical trials using combined targeted therapy and immunotherapy for melanoma as well as other cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1970.

Abstract 4796: Treatment with chromatin remodeling agents increases MAGE-A3 expression in pancreatic cancer and enhances antigen-specific recognition by T lymphocytes

Pancreatic cancer is the fourth leading cause of cancer death in the United States and is frequently lethal despite aggressive medical and surgical treatment. Better forms of treatment are needed. One promising area of investigational treatment for patients with pancreatic cancer involves the use of immunotherapy. Approaches to cancer immunotherapy have evolved over the past 20 years resulting in improved response rates to therapy. This form of treatment was founded on the adoptive transfer of tumor-infiltrating lymphocytes in the treatment of melanoma. More recently, innovative strategies involving genetic modification of peripheral blood lymphocytes to express T cell receptors targeting tumor antigens have been developed and show promise in generating anti-tumor responses against a wide range of malignancies beyond melanoma. Vaccines and immunomodulatory agents also exist.

MAGE-A3 is a cancer-testis antigen (CTA) and is expressed in up to 40% of pancreatic cancer tumors thus may be a suitable target in the treatment of this malignancy. It has a favorable expression profile, which is limited to neoplastic tissue and non-MHC bearing germ cell tissues. Furthermore, expression of MAGE-A3 (and other CTA) may be up-regulated in cancer cells by treatment with chromatin remodeling agents. Vaccines targeting MAGE-A3 are currently in use.

The goal of these studies was to explore epigenetic mechanisms to enhance expression of the MAGE-A3 CTA in pancreatic cancer in an effort to improve recognition of these tumors by MAGE-A3-specific T lymphocytes as a basis for combined therapy against this disease.

Pancreatic cancer cell lines were cultured with chromatin remodeling agents 5-aza-2′-deoxycytidine (5-AZA), Valproate (VALP), 5-AZA + VALP, or with the chemotherapeutic agent Gemcitabine (Gem). Expression of MAGE-A3 (and other CTA) was assayed at the mRNA or protein level. Untreated and treated pancreatic cancer cell lines were co-cultured with antigen-specific T lymphocytes (generated by transduction of lymphocytes with MAGE-A3-specific T cell receptors) and reactivity was measured via interferon gamma release.

Treatment of pancreatic cancer cell lines with chromatin remodeling agents resulted in increased levels of CTAs (including MAGE-A3) and was synergistic when used in combination. The increased MAGE-A3 expression was associated with improved recognition by antigen-specific T lymphocytes. Treatment with Gemcitabine had no effect on CTA expression or antigen-specific recognition.

These findings suggest that expression of CTA and MAGE-A3 in pancreatic cancer cells may be upregulated via treatment with chromatin remodeling agents, rendering them more susceptible to antigen-specific T lymphocytes. These data provide the groundwork for further studies addressing combined epigenetic therapy and immunotherapy for pancreatic cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4796.