Haley Dahl

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, interleukin‐1 (IL‐1), represses AR messenger RNA (mRNA) levels and activity in AR‐positive (AR + ) PCa cell lines concomitant with the upregulation of prosurvival biomolecules. Thus, we contend that IL‐1 can select for AR‐independent, treatment‐resistant PCa cells. Methods To begin to explore how IL‐1 signaling leads to the repression of AR mRNA levels, we performed comprehensive pathway analysis on our RNA sequencing data from IL‐1‐treated LNCaP PCa cells. Our pathway analysis predicted nuclear factor kappa B (NF‐κB) p65 subunit (RELA), a canonical IL‐1 signal transducer, to be significantly active and potentially regulate many genes, including AR . We used small interfering RNA (siRNA) to silence the NF‐κB family of transcription factor subunits, RELA , RELB , c‐REL , NFKB1 , or NFKB2 , in IL‐1‐treated LNCaP, C4‐2, and C4‐2B PCa cell lines. C4‐2 and C4‐2B cell lines are castration‐resistant LNCaP sublines and represent progression toward metastatic PCa disease, and we have previously shown that IL‐1 represses AR mRNA levels in C4‐2 and C4‐2B cells. Results siRNA revealed that RELA alone is sufficient to mediate IL‐1 repression of AR mRNA and AR activity. Intriguingly, while LNCaP cells are more sensitive to IL‐1‐mediated repression of AR than C4‐2 and C4‐2B cells, RELA siRNA led to a more striking derepression of AR mRNA levels and AR activity in C4‐2 and C4‐2B cells than in LNCaP cells. Conclusions These data indicate that there are RELA‐independent mechanisms that regulate IL‐1‐mediated AR repression in LNCaP cells and suggest that the switch to RELA‐dependent IL‐1 repression of AR in C4‐2 and C4‐2B cells reflects changes in epigenetic and transcriptional programs that evolve during PCa disease progression.

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.

Abstract Background Breast (BCa) and prostate (PCa) cancers are hormone receptor (HR)-driven cancers. Thus, BCa and PCa patients are given therapies that reduce hormone levels or directly block HR activity; but most patients eventually develop treatment resistance. We have previously reported that interleukin-1 (IL-1) inflammatory cytokine downregulates ERα and AR mRNA in HR-positive (HR + ) BCa and PCa cell lines, yet the cells can remain viable. Additionally, we identified pro-survival proteins and processes upregulated by IL-1 in HR + BCa and PCa cells, that are basally high in HR − BCa and PCa cells. Therefore, we hypothesize that IL-1 confers a conserved gene expression pattern in HR + BCa and PCa cells that mimics conserved basal gene expression patterns in HR − BCa and PCa cells to promote HR-independent survival and tumorigenicity. Methods We performed RNA sequencing (RNA-seq) for HR + BCa and PCa cell lines exposed to IL-1 and for untreated HR − BCa and PCa cell lines. We confirmed expression patterns of select genes by RT-qPCR and used siRNA and/or drug inhibition to silence select genes in the BCa and PCa cell lines. Finally, we performed Ingenuity Pathway Analysis (IPA) and used the gene ontology web-based tool, GOrilla, to identify signaling pathways encoded by our RNA-seq data set. Results We identified 350 genes in common between BCa and PCa cells that are induced or repressed by IL-1 in HR + cells that are, respectively, basally high or low in HR − cells. Among these genes, we identified Sequestome-1 ( SQSTM1/p62 ) and SRY ( Sex-Determining Region Y ) -Box 9 ( SOX9 ) to be essential for survival of HR − BCa and PCa cell lines. Analysis of publicly available data indicates that p62 and SOX9 expression are elevated in HR-independent BCa and PCa sublines generated in vitro, suggesting that p62 and SOX9 have a role in acquired hormone receptor independence and treatment resistance. We also assessed HR − cell line viability in response to the p62-targeting drug, verteporfin, and found that verteporfin is cytotoxic for HR − cell lines. Conclusions Our 350 gene set can be used to identify novel therapeutic targets and/or biomarkers conserved among acquired (e.g. due to inflammation) or intrinsic HR-independent BCa and PCa.

Abstract 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.