Enhanced Antitumor Efficacy of MUC-16 Targeted T Cells Further Modified to Constitutively Express the IL-12 Cytokine in a Syngeneic Model of Ovarian Cancer,

Abstract 4176

T cells may be genetically modified to recognize tumor associated antigens (TAAs) through the introduction of genes encoding artificial T cell receptors termed chimeric antigen receptors (CARs). We have constructed SFG retroviral vectors encoding first (4H11mz) and second (4H11m28mz) generation CARs as well as IL-12 modified CAR (4H11m28mzIRESmIL12) targeted to the retained extra-cellular domain of MUC16, termed MUC-CD. This antigen is over-expressed on most ovarian carcinoma tumor cells. IL-12 is a potent inducer of a Th1 CD4⁺ T cell response and serves as a “signal 3” in concert with TCR activation (signal 1) and CD28 co-stimulation (signal 2) to CD8⁺ T cells, resulting in optimized clonal expansion and effector function. In order to mimic the clinical setting, we generated a syngeneic tumor model using the C57BL6 (B6) mice intraperitoneally (i.p.) injected with ID8(MUC-CD) cells. In our studies treatment of mice bearing established ID8(MUC-CD) ovarian tumor with MUC-CD specific T cells expressing IL-12 gene, in contrast to T cells targeted to MUC-CD alone, fully eradicate advanced intraperitoneal ovarian tumors. The mechanism of IL-12 expressing MUC-CD targeted T cell antitumor efficacy was mediated through enhanced persistence and engraftment of modified T cells, as well as the ability of IL-12 secreting T cells to recruit endogenous T cells to the tumor site. Furthermore, we observed elevated secretion of the pro-inflammatory cytokines (IFN-g and TNF-a) in the serum of IL-12 treated mice, compared to 4H11m28mz and control CD19 targeted T cell treated groups. Treatment of B6 mice with MUC-CD targeted T cells expressing IL-12 gene was dependent upon recruitment of the NK and NKT cells to the tumor site. Finally, we demonstrated the ability of IL-12 secreting T cells to overcome the immunosuppressive tumor microenvironment by switching the phenotype of the tumor-associated macrophages (TAMs) from a predominately immunosuppressive M2 to an immunostimulatory M1 phenotype. These data, obtained in the context of a clinically relevant syngeneic tumor model supports the application of this approach in the treatment of the patients with relapsed ovarian carcinomas.