Abstract 530: Phosphatidylserine-targeting antibody combined with chemoradiation enhances systemtic anti-tumor immunity

Abstract

Abstract The discovery of immune checkpoint blockades have resulted in significant clinical benefits for patients with metastatic cancers including non-small cell lung cancer (NSCLC). Nevertheless, a large proportion of patients do not respond to such therapy. Strategies to enhance the therapeutic efficacy of cancer immunotherapy among a larger group of patients are urgently needed. Increasing the recognition of cancer cells by immune system may enhance response to immunotherapies. Tumor-associated macrophage (TAM) is the most abundant immune cell in most solid tumors, and is critical in bridging innate and adaptive immune system functions. Cancer cells overexpress multiple immune suppressive molecules including phosphatidylserine (PS) to inhibit immunological functions of TAMs. PS expression can be enhanced by cancer therapeutics such as radiation to induce immune suppression. Our results show that radiation increased expression of PS on lung cancer cells. The combination of PS blocking antibody with radiation decreased immune-suppressive phagocytosis and enhanced antigen presentation of macrophages. In murine lung cancer models, combination treatment of PS blockade and chemoradiation more effectively controlled tumor growth and prolonged survival than each treatment used alone. In a bilateral lung cancer tumor model, addition of PS blockade to chemoradiation promoted cytotoxic T cell infiltration and induced tumor growth inhibition of the non-irradiated tumors. Together, our results demonstrate that PS-targeting antibodies may be combined with chemoradiation to enhance intrinsic tumor immunogenicity and activate systemic anti-tumor immune responses. This approach may provide new routes for improving the efficacy of modern immunotherapeutics. Citation Format: Yifan Wang, Zhigang Liu, Weiye Deng, Betty Y. Kim, Steven H. Lin, Wen Jiang. Phosphatidylserine-targeting antibody combined with chemoradiation enhances systemtic anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 530.