Chimeric antigen receptor (CAR) T cells genetically engineered to deliver IL-12 to the tumor microenvironment in ovarian cancer.

Abstract

141 Background: Chimeric antigen receptor (CAR) T cell therapy for solid tumor malignancies has not shown the same degree of clinical efficacy observed in hematologic malignancies such as B-ALL. The presence of an immunosuppressive cellular and cytokine microenvironment has been hypothesized as one reason for the failure of adoptive immunotherapy for solid tumors. In ovarian cancer, myeloid derived suppressor cells (MDSC) and immunosuppressive cytokines in the ascitic microenvironment have been reported. IL-12 is a proinflammatory cytokine produced by macrophages, dendritic cells (DC), and NK cells, and it has been shown to increase proliferation of T cells, induce differentiation of type 1 T helper cells, inhibit regulatory T cells, promote maturation of DCs, and enhance antigen presentation by macrophages. We hypothesize that CAR T cells genetically modified to constitutively secrete IL-12 will overcome a hostile tumor microenvironment in a peritoneal carcinomatosis model of ovarian cancer. Methods: CAR T cells were generated from retroviral transduction of second generation and IL-12 modified CAR’s directed to either an irrelevant CD-19 antigen or Muc16ecto. C57BL/6 mice were inoculated i.p with syngeneic ovarian cancer cells and treated with various CAR T cells. Results: Here we report increased production of IL-12, improved proliferation and cytotoxic activity of 4H1128ζ-IL12 CAR T cells. Further, we show increased levels of inflammatory cytokines at 24 and 48hrs after treatment of tumor-bearing mice, leading to increased survival at advanced stages of disease. Animals treated with 4H1128ζ-IL12 CAR T cells had decreased levels of F4/80+ CD11b+MDSCs. Genetic analysis of recovered MDSCs from the ascites of treated animals showed skewing towards an M1-phenotype via upregulation of cytokines, chemokines, MHC-II, and downregulation of Arg1. Furthermore, clodronate-mediated depletion of TAM’s further enhanced survival in mice treated with 4H1128ζ-IL12 CAR T cells. Conclusions: These results demonstrate the mechanisms of efficacy of localized delivery of IL-12 to the tumor microenvironment by 4H1128ζ-IL12 CAR T cells.