Introduction: The cancer testis (CT) antigens, such as NY-ESO1, are considered ideal targets for immunotherapy as they are highly immunogenic and their restricted expression malignancies and not normal tissue except testis. However, the expression of CT antigen is downregulated in many tumor types, including breast cancer due to DNA methylation. DNA methylation is a common epigenetic mechanism to regulate gene expression and phenotype and maintain DNA integrity and stability. DNA methylation inhibition can induce NY-ESO1 expression on tumor cells and sensitize them to NY-ESO1 specific T cells. NY-ESO1 targeted T cell receptors (TCR) have been successfully used to engineer T cells for adoptive T cell therapy (ACT). We hypothesize that incorporating a dominant-negative TGFβ receptor II (dnTGFβRII) into the NY-ESO-1 TCR construct to transduce T cells combined with epigenetic modulator treatment may improve T cell effector function in immunosuppressive tumor microenvironment.

Methods: Seven different human breast cancer cell lines were treated with epigenetic modulators at different doses and analyzed by flow cytometry to check the increase in expression of NY-ESO1 antigen and HLA-A2.1. Eight-weeks or older NSG mice were inoculated with HLA-A2.1+, NY-ESO negative at baseline breast cancer cells subcutaneously. PBMCs from healthy donors were transduced with a HLA-A2.1 NY-ESO1 TCR with/without dnTGFβRII two day after activation with OKT3 antibody plus IL-2. The transduction efficiency was confirmed by flow cytometry prior to ACT. Equal numbers of TCR+ cells were injected 10 days after tumor inoculation. Mice were then monitored for tumor growth till endpoint. The spleens and tumors were collected for further analysis of immunophenotype and function.

Results: The expression of NY-ESO1 was inducible with epigenetic modulation in the majority of breast cancer cell-lines tested (5/7). More than 60% of Vβ+ (marker for surface expression of specific TCR) cells were observed after retroviral transduction to PBMCs. The transduced NY-ESO1 TCR/dnTGFβRII cells with epigenetic modulator were successfully able to infiltrate into tumor microenvironment in higher numbers and control cancer growth of inoculated tumor significantly (p<0.01) in comparison to control tumor and control NY-ESO1 TCR only groups. The tumor infiltrated lymphocytes (TILs) from NY-ESO1 TCR/dnTGFβRII with treatment showed that regulatory T cells and cytotoxic T cells were significantly lower and higher, respectively.

Conclusions: Epigenetic modification enhances the cytotoxicity of TCR engineered T cells with dnTGFβRII. Our results demonstrate the feasibility of combined epigenetic modulation and TCR-T treatment for breast cancer patients.

Citation Format: Satoko Matsueda, Kunle Odunsi, Richard C. Koya. TGFβ blockade and epigenetic modulation for cancer treatment: Efficient breast cancer targeted therapy with TCR-T cell transfer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B36.