Our data supports that IL-1 reprograms AR PCa cells to mimic AR PCa gene expression patterns that favor AR-targeted treatment resistance and cell survival.

No abstract

Background: The Androgen Receptor (AR) nuclear transcription factor is a therapeutic target for prostate cancer (PCa). Unfortunately, patients can develop resistance to AR-targeted therapies and progress to lethal disease, underscoring the importance of understanding the molecular mechanisms that underlie treatment resistance. Inflammation is implicated in PCa initiation and progression and we have previously reported that the inflammatory cytokine, . CC-BY-NC-ND 4.

Estrogen receptor α (ERα)low/− tumors are associated with breast cancer (BCa) endocrine resistance, where ERα low tumors show a poor prognosis and a molecular profile similar to triple negative BCa tumors. Interleukin‐1 (IL‐1) downregulates ERα accumulation in BCa cell lines, yet the cells can remain viable. In kind, IL‐1 and ERα show inverse accumulation in BCa patient tumors and IL‐1 is implicated in BCa progression. IL‐1 represses the androgen receptor hormone receptor in prostate cancer cells concomitant with the upregulation of the prosurvival, autophagy‐related protein, Sequestome‐1 (p62/SQSTM1; hereinafter, p62); and given their similar etiology, we hypothesized that IL‐1 also upregulates p62 in BCa cells concomitant with hormone receptor repression. To test our hypothesis, BCa cell lines were exposed to conditioned medium from IL‐1‐secreting bone marrow stromal cells (BMSCs), IL‐1, or IL‐1 receptor antagonist. Cells were analyzed for the accumulation of ERα, progesterone receptor (PR), p62, or the autophagosome membrane protein, microtubule‐associated protein 1 light chain 3 (LC3), and for p62‐LC3 interaction. We found that IL‐1 is sufficient to mediate BMSC‐induced ERα and PR repression, p62 and autophagy upregulation, and p62‐LC3 interaction in ERα+/PR+ BCa cell lines. However, IL‐1 does not significantly elevate the high basal p62 accumulation or high basal autophagy in the ERα−/PR− BCa cell lines. Thus, our observations imply that IL‐1 confers a prosurvival ERα−/PR− molecular phenotype in ERα+/PR+ BCa cells that may be dependent on p62 function and autophagy and may underlie endocrine resistance.

Chronic inflammation promotes prostate cancer (PCa) initiation and progression. We previously reported that acute intereluekin-1 (IL-1) exposure represses androgen receptor (AR) accumulation and activity, providing a possible mechanism for IL-1-mediated development of androgen- and AR-independent PCa. Given that acute inflammation is quickly resolved, and chronic inflammation is, instead, co-opted by cancer cells to promote tumorigenicity, we set out to determine if chronic IL-1 exposure leads to similar repression of AR and AR activity observed for acute IL-1 exposure and to determine if chronic IL-1 exposure selects for androgen- and AR-independent PCa cells. We generated isogenic sublines from LNCaP cells chronically exposed to IL-1α or IL-1β. Cells were treated with IL-1α, IL-1β, TNFα or HS-5 bone marrow stromal cells conditioned medium to assess cell viability in the presence of cytotoxic inflammatory cytokines. Cell viability was also assessed following serum starvation, AR siRNA silencing and enzalutamide treatment. Finally, RNA sequencing was performed for the IL-1 sublines. MTT, RT-qPCR and western blot analysis show that the sublines evolved resistance to inflammation-induced cytotoxicity and intracellular signaling and evolved reduced sensitivity to siRNA-mediated loss of AR, serum deprivation and enzalutamide. Differential gene expression reveals that canonical AR signaling is aberrant in the IL-1 sublines, where the cells show constitutive PSA repression and basally high KLK2 and NKX3.1 mRNA levels and bioinformatics analysis predicts that pro-survival and pro-tumorigenic pathways are activated in the sublines. Our data provide evidence that chronic IL-1 exposure promotes PCa cell androgen and AR independence and, thus, supports CRPCa development.