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

Abstract

3050 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. The presence of an immunosuppressive cytokine and cellular microenvironment has been hypothesized as one reason for the failure of adoptive immunotherapy for solid tumors. In ovarian cancer, the presence of tumor associated macrophages (TAMs) 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 has been shown to increase proliferation of T cells and enhance antigen presentation by macrophages. We hypothesized that CAR T cells genetically modified to constitutively secrete IL-12 would 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. Results: Here we report increased production of IL-12, improved proliferation and cytotoxic activity of 4H1128-IL12 CAR T cells. 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. Mice treated with 4H1128-IL12 CAR T cells had decreased levels of F4/80+ CD11b+TAM’s. Genetic analysis of recovered TAM’s from the ascites of treated animals showed skewing towards an M1-phenotype via upregulation of cytokines, chemokines, MHC-II and downregulation of Arg1. Recovered 4H1128-IL12 CAR T cells showed upregulation of FAS-L and recovered TAMs showed increased expression of FAS suggesting FAS/FAS-L engagement was responsible for decreased TAMs. Blocking the FAS/FAS-L pathway led to recovery of TAM populations in 4H1128-IL12 treated mice. Finally, clodronate-mediated depletion of TAM’s further enhanced survival in mice treated with 4H1128-IL12 CAR T cells. Conclusions: These results demonstrate the mechanisms of efficacy of localized delivery of IL-12 to the tumor microenvironment by 4H1128-IL12 CAR T cells.