Abstract 5575: Androgen receptor stimulation with 5α-dihydrotestosterone (DHT) decreases PD-L1 expression in androgen-responsive thyroid cancer cells

Abstract

Abstract Thyroid cancer is the most rapidly increasing cancer in the US with 64,300 new cases expected in 2016. However, there is a disparity in the incidence of thyroid cancer between females and males, with women (49,350 expected cases) developing thyroid cancer three times more often than men (14,950 expected cases). Immune elimination of nascent tumor cells may explain the difference in disease incidence between men and women. To address this hypothesis, the effect of androgen on the expression of immune checkpoint molecules in an androgen responsive-thyroid cancer cell line was examined. The undifferentiated thyroid cancer cell line, 8505C, does not express a functional androgen receptor (AR). 84E7 is a clone of 8505C that was transfected with an AR containing plasmid resulting in constitutively expressed AR. Transcriptome analysis via RNASeq was performed on 8505C and 84E7, with and without 5α-dihydrotestosterone (DHT) treatment. Raw sequencing reads were aligned to the UCSC hg19 human reference genome with Tophat, and Cufflinks was used to measure transcript abundances in Reads Per Kilobase of exon model per Million mapped reads (RPKM) as well as to find genes with statistically significant changes in expression. DHT treatment of 84E7 resulted in >2 fold expression changes in 1,552 genes. We examined the immune checkpoint ligands expressed on 84E7 such as CD80, CD86, PD-L1, PD-L2, ICOSL, B7-H3, B7-H4, HVEM, 4-1BBL, OX40L, CD70, CD40, and GAL9. PD-L1 was the sole immune checkpoint molecule that exhibited a significant expression change in DHT-treated 84E7 cells with a 1.8 log2 fold decrease (p=0, q=0), or 72% reduction in mRNA content. Additional studies confirmed the RNASeq results and provide evidence of both qualitative (immunofluorescence) and quantitative (flow cytometry and western blotting) decreases in PD-L1 expression with DHT treatment. These results are significant in that PD-L1 is produced by tumor cells as a strategy for subverting and evading the immune response, specifically T cells, allowing for continued tumor growth and metastases. In the thyroid, the presence of activated androgen receptors could lead to an environment that is more favorable for immune system activation and may help eliminate nascent thyroid cancer cells. Thus, men may experience a decreased incidence of thyroid cancer due to an enhanced and less inhibited anti-tumor environment. Citation Format: Timmy J. O'Connell, Melanie Jones, Anvita Gupta, Tali Lando, Deya Jourdy, Edward Shin, Augustine Moscatello, Raj Tiwari, Jan Geliebter. Androgen receptor stimulation with 5α-dihydrotestosterone (DHT) decreases PD-L1 expression in androgen-responsive thyroid cancer cells [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 5575. doi:10.1158/1538-7445.AM2017-5575