Abstract 3223: Androgen receptor stimulation decreases PD-L1 expression in androgen-responsive thyroid cancer cells

Women develop thyroid cancer more often than men; however, when men develop thyroid cancer, the disease course is more lethal, with a mortality rate that is two to three fold higher than in females. Immune elimination of nascent tumor cells may explain the differences in disease occurrence/course between men and women. To address this possibility, we examined the effect of androgen on the expression of immune checkpoint molecules in an androgen responsive-thyroid cancer cell line. 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 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 as per Trapnell et al (2012). RNASeq data indicated that DHT treatment of 8505C cells does not result in a significant change in gene expression (only 14 of 23,285 genes), consistent with the lack of a functional androgen receptor. In contrast, DHT treatment of 84E7 resulted in >2 fold expression changes in 1,552 genes. Examination of the immune checkpoint molecules CD28, CD80, CD86, CTLA-4, PD-1, PD-L1, PD-L2, TIM-3, TIM-3L, 4-1BB, 4-1BBL, OX40, and OX40L revealed that in DHT-treated 84E7 cells, PD-L1 was the sole immune checkpoint molecule that exhibited a significant expression change with a 1.8 log2 fold decrease (p = 0, q = 0), or 72% reduction in mRNA content. This is potentially significant as 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 androgen-activated androgen receptors could perhaps lead to an environment that is more favorable for the immune system and may help eliminate nascent thyroid cancer cells. Thus, men may experience a decreased incidence of thyroid cancer due to an enhanced (less inhibited) anti-tumor environment. However, failure of this system and a subsequent increase in PD-L1 expression may help to explain the onset and severity of thyroid cancer in males. This finding opens the possibility for the use of immune checkpoint inhibitors in the treatment of thyroid cancer. Citation Format: Timmy O’Connell, Melanie Jones, Anvita Gupta, Augustine Moscatello, Raj K. Tiwari, Jan Geliebter. Androgen receptor stimulation decreases PD-L1 expression in androgen-responsive thyroid cancer cells. [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 3223.