Immunohistochemical, ChIP, and microarray analysis reveals how stromal AR controls prostate cancer outcome through fibroblast specific action of androgen signalling on ECM production and DNA licensing
D. Leach1, E. Need1, D. DeFranco2, C. Pinnock3, S. Chopra3,4, R. Taylor5, G. Risbridger5 & G. Buchanan1
A breakdown in stromal-epithelial interactions mediated by androgens is emerging as a key factor in prostate cancer (PCa) aetiology and progression. Currently however, we have limited knowledge of the mechanics of androgen and androgen receptor (AR) action in prostate stroma, or how dysfunction in that compartment contributes to the disease process.
In this study, immunohistochemical analysis of 64 PCa samples revealed an inverse relationship between stromal AR content and both primary tumour burden and PCa-related death (P<0.05). In contrast, epithelial AR content was positively related to Gleson stage and tumour burden but not outcome (P<0.03). These relationships were not evident in patient-matched BPH samples. In order to understand how stromal AR might inhibit progression, we investigated androgen action in the AR positive prostate myofibroblast cell line, pshTERT-AR. By chromatin immunoprecipitation, we find lineage-specific chromatin occupancy of regulatory elements by the AR. These differences in DNA interactions leads to divergent enhancement of functional pathways and physiological response. Microarray profiling revealed that only 10% of the genes regulated by androgen in myofibroblasts were also regulated in PCa epithelial cells. This distinct set of genes regulated by androgens lead to regulation of adhesion and ECM production pathways specifically in fibroblasts, as well as opposing effects on apoptosis and cell cycle pathways in comparison to epithelial cells. A key outcome is divergent growth responses, with androgens inhibiting fibroblast proliferation (66% control at 5 days; P=0.002) potentially via DNA licensing protein, FBXO32, but stimulating epithelium (50%, P=0.001). Importantly, androgens were also found to alter the constituents of fibroblast-deposited extracellular matrix (ECM), resulting enhanced anchorage of both fibroblasts (40%; P<0.05) and PCa epithelia (35%, P<0.05). In summary, the loss of fibroblast/stromal AR is predicted to stimulate fibroblast proliferation, dysregulate stromal-epithelial interactions in the prostate microenvironment, decrease ECM adhesive characteristics and create an environment that predisposes to epithelial metastasis.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details unavailable.