Abstract 2637: Anti-tumor activity of cisplatin is enhanced by PD-1 blockade in preclinical models of head and neck squamous cell carcinoma

Rationale: Cisplatin, which remains the most commonly used systemic drug for head and neck squamous cell carcinoma (HNSCC), reduces numbers of circulating immune cells. However, recent studies suggest that cisplatin may enhance some aspects of anti-tumor immunity in the tumor microenvironment. We previously found that cisplatin increases expression of major histocompatibility (MHC) class I and programmed death ligand 1 (PD-L1) in HNSCC cell lines in vitro. Methods: In the current study, we investigated other components of the antigen processing machinery (APM) by flow cytometry following treatment with cisplatin. Using the syngeneic mouse oral cancer 1 (MOC1) model of HNSCC, we then investigated the effects of cisplatin and anti-PD-1 antibody, alone or in combination, on tumor growth and survival. Results: Using three different HNSCC cell lines, we found that levels of the APM components LMP2, ERp57 and calreticulin increased in all cell lines treated with cisplatin, whereas TAP1/2 increased dramatically only in one cisplatin-treated cell line with wildtype TP53 (UMSCC-74A). In MOC1 tumor-bearing mice, tumor growth was partially delayed by treatment with cisplatin and anti-PD-1 antibody alone and substantially delayed when these agents were given in combination, with resultant increased survival. Comparison of different treatment schedules suggested that concurrent administration is more effective than giving cisplatin one day prior to anti-PD-1 or giving anti-PD-1 one day prior to cisplatin. Conclusions: Despite upregulating PD-L1 on tumor cells and decreasing levels of circulating immune cells, cisplatin may enhance some aspects of anti-tumor immunity in the tumor microenvironment. While no mice were cured with concurrent cisplatin and anti-PD-1 antibody, tumor growth was substantially delayed. These results suggest a rationale for combining cisplatin and anti-PD-1 monoclonal antibodies, perhaps with radiation or other therapies, in additional preclinical studies and clinical trials of HNSCC. Supported by NIDCD intramural project ZIA-DC-DC000090. Citation Format: Linda Tran, Clint T. Allen, So-Jin Park, Roy Xiao, Carter Van Waes, Nicole C. Schmitt. Anti-tumor activity of cisplatin is enhanced by PD-1 blockade in preclinical models of head and neck squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2637. doi:10.1158/1538-7445.AM2017-2637