Abstract A074: Selective Inhibition of HDAC6 augments T-cell central memory and enhances anti-tumor functions: Implications in TIL therapy

Abstract

Abstract Histone deacetylases (HDACs) are a family of epigenetic modulators responsible for regulating gene expression. As key players in orchestrating both tumor and immune responses, HDACs have received attention for their possible role in cancer immunotherapy. While pan-HDAC inhibitors directly impact tumor growth, their broad targeting can be detrimental to the immune system. In this sense, HDAC selective inhibition becomes attractive as a strategy to minimize off-target effects. Here a novel role of targeting HDAC6 in T-cells with potential implications for melanoma immunotherapy is explored. Adoptive T-cell therapy is an effective treatment for metastatic melanoma, reaching objective clinical responses in half of patients undergoing tumor infiltration lymphocyte (TIL) therapy. However, lack of persistence of reactive T-cells is a major reason why patients fail to sustain long-term responses to treatment. The presence of T-cell memory populations is associated with prolonged responses to TIL. Herein we have shown that HDAC6-selective inhibition by ricolinostat increased the central memory phenotype of human CD4 and CD8 T-cells (p<0.01 and p<0.05, respectively), as indicated by CD45RO, CD45RA, CD62L and/or CCR7 surface markers. While a decrease in the naïve, effector and effector memory subsets occurred, no differences in cell viability were observed. Accordingly, similar ricolinostat-induced central memory enhancement was seen in CD4 and CD8 T-cells from the peripheral blood of melanoma patients (p<0.01 and p<0.05, respectively). Ultimately, ricolinostat led to accumulation of a central memory phenotype for TIL derived from various cell preparations (e.g. tumor digest, pre- and post-rapid expansion in vitro), with p values <0.05. Intriguingly, Th2 cytokine production (i.e. IL-4 p<0.01, IL-6 p<0.001 and IL-10) was impaired in T-cells from melanoma patients treated with ricolinostat, while no differences occurred on IL-2, IFNg, TNF or IL-17a secretion. Functionally, TILs isolated from patient-derived melanoma fragments cultured in the presence of ricolinostat exhibited increased proportion of CD8 T-cells producing IFNg and CD107a cytolytic molecules (50% vs 35%, p<0.05). Moreover, no negative impact on T-cell viability or proliferation was observed following ricolinostat treatment. No detrimental effects were observed in the yield of TIL from melanoma fragments. Cytotoxicity in vitro was also evaluated. Relative to a melanoma only control group, ricolinostat pre-treatment of TILs or concomitantly with tumor cells induced 70% killing of HLA matched melanoma cells, while control-treated TILs resulted in 50% cell death. In vivo, adoptive transfer of rocilinostat-treated murine T-cells improved the anti-melanoma effect in a B16F10 model (day 25 mean tumor volume 800 vs. 2200 cubic mm). Ex vivo characterization of the memory T-cell distribution in the lymph nodes demonstrated increased CD44+CD62L+ T-cells upon HDAC6-selective inhibition (CD8+ 32.8% vs 21.8%; CD4+ 4.71% vs 2.3%), suggesting a role of HDAC6 in the formation or distribution of memory CD4+ and CD8+ T-cells. The results suggest a positive impact of HDAC6-selective inhibition on TIL therapy and the resulting anti-melanoma response in vivo. While further dissection of molecular mechanism(s) is essential, the data described provide a rationale for targeting HDAC6 to augment melanoma immunotherapy. Citation Format: Andressa Sodre Laino, David M. Woods, Amod Sarnaik, Jeffrey Weber, Eduardo M. Sotomayor. Selective Inhibition of HDAC6 augments T-cell central memory and enhances anti-tumor functions: Implications in TIL therapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A074.