Abstract B38: Increasing tumor-infiltrating CD8+ T cell response and checkpoint inhibitor efficacy by enzymatic reduction of tumor hyaluronan in a murine syngeneic pancreatic cancer model

Abstract

Abstract Inducing an efficient CD8+ T-cell-mediated antitumor immune response at the tumor site is critical for successful immunotherapy. The trafficking and activation of these effector CD8+ T cells to tumors are often inhibited by various immunosuppressive mechanisms in the tumor microenvironment (TME). Hyaluronan (HA), a glycosaminoglycan that accumulates in the TME of many solid tumors, is associated with rapid tumor progression, poor prognosis and increased immunosuppression. We have previously demonstrated in preclinical models that enzymatic degradation of TME HA by intravenous PEGylated recombinant human hyaluronidase PH20 (PEGPH20) enhances anti-Programmed death-ligand 1 (anti-PD-L1) efficacy and increases access of immune cells to the tumor (Clift, AACR 2017 poster #641). In this study, we aimed to extend these findings to a murine syngeneic pancreatic cancer model to explore the pan-tumor potential of combining PEGPH20 and anti-PD-L1 to improve anti-tumor immune response. To test this hypothesis in a pancreatic tumor model, Pan02 murine pancreatic adenocarcinoma cells were engineered to over-express hyaluronan synthase-3 (Pan02/Has3). Peritibial Pan02/Has3 tumors accumulated 10-fold higher levels of HA (1668 ng/mg) compared with Pan02 parental tumors (166 ng/mg) as determined by HA ELISA. HA accumulating Pan02/Has3 tumors were treated with combinations of PEGPH20 and/or anti-PD-L1, and tumor growth was monitored. Treatment with PEGPH20 (1mg/kg, biweekly) resulted in nearly complete removal of HA at 24hrs, the time point at which anti-PD-L1 treatment (5mg/kg, biweekly) was initiated. Tumor burden growth was reduced by 50% with combination of PEGPH20 and anti-PD-L1 versus 21% with PEGPH20 alone (p<0.01) or 5% with anti-PD-L1 alone (p<0.01). To elucidate the underlying mechanism, tumor infiltrating immune cells were analyzed by flow cytometry. We observed a significant increase in the numbers of cytotoxic CD8+ tumor infiltrating lymphocytes (TILs) in tumors treated with PEGPH20 alone compared with the vehicle group. Similarly, tumors treated with PEGPH20 in combination with anti-PD-L1 contained higher numbers of CD8+ TILs, CD4+ TILs, and Natural killer (NK) cells, and had increased CD8:Treg ratios compared to anti-PD-L1 treatment alone. Taken together, our data suggest that tumor HA accumulation may act as a barrier to immune cell access in a mouse model of pancreatic cancer, and that enzymatic reduction of HA can facilitate access of CD8+ T cells and enhance anti-PD-L1 efficacy. These findings are consistent with prior studies and support the ongoing clinical evaluation of combining PEGPH20 with immune checkpoint inhibitors to improve anti-tumor efficacy in HA-accumulating tumors. Citation Format: Benjamin Thompson, Trevor Kimbler, Barbara Blouw, Renee Clift, Yujun Huang, Sanna Rosengren, Curtis B. Thompson, Jisook Lee. Increasing tumor-infiltrating CD8+ T cell response and checkpoint inhibitor efficacy by enzymatic reduction of tumor hyaluronan in a murine syngeneic pancreatic cancer model [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B38.