Abstract 4977: Immunogenic chemotherapy synergize PD-1 blockade by enhancing dendritic cells infiltration in triple-negative breast cancer (TNBC)

Abstract

Abstract Targeting immune checkpoints such as programmed cell death protein 1 (PD1), programmed cell death 1 ligand 1 (PDL1) has achieved noteworthy benefit in multiple cancers. However, their efficacy remains unsatisfactory in triple-negative breast cancer (TNBC). Breast cancer is not highly mutagenic and immune checkpoints blockade therapies for TNBC is not as effective as for melanoma or lung cancer with high mutation rates. Combination of different modalities offers an opportunity to enhance their effect. We studied the synergistic effect of cancer chemotherapy and immunotherapy in TNBC mouse model. Here we report that the combination of Doxisome (liposomal encapsulated formulation of Doxorubicin) and anti-PD-1 antibody suppresses tumor growth, reduces lung metastasis and improves survival of mice bearing 4T1-triple negative breast cancer. Moreover, the combination of Doxisome and anti-PD-1 was able to overcome low dose Doxisome resistance in mouse models of TNBC. The success of anticancer chemotherapy is linked to a durable immune response of targeting tumor. We present evidence that the synergistic therapeutic activity of Doxisome with anti-PD1 blockade results in enhanced T cell anti-tumor immune responses. Moreover, the synergetic effect is due to increased dendritic cells (DCs) infiltration in tumor microenvironment, which internalize tumor antigens and subsequently activate tumor-reactive T cells. In TNBC mouse model, by combining anti-PD1 checkpoint blockade while shifting the immune response towards CD4+ Th1 with Doxisome, immune tolerance to TNBC tumor can be overcome. Enhancing antigen presenting cells (APCs, e.g. DCs) infiltration by immunogenic chemotherapy and T cell activation by anti-PD1 blockade increase therapy response in TNBC. These results provide rationale for several newly planned clinical trials combining immunogenic chemotherapy with PD-1 or PD-L1 blockade in breast cancer and exploration of such a combination in others solid tumors. Citation Format: Xiangliang Yuan, Yi Xiao, Wenling Kuo, Dihua Yu. Immunogenic chemotherapy synergize PD-1 blockade by enhancing dendritic cells infiltration in triple-negative breast cancer (TNBC). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4977.