Twist1/Dnmt3a and miR186 establish a regulatory circuit that controls inflammation-associated prostate cancer progression

Abstract

Increasing evidences suggest that inflammatory microenvironment has a crucial role in prostate cancer (PCa) progression; however, the underlying mechanisms are unclear. Here, we used the inflammation-associated prostate cellular transformation model to screen out a crucial microRNA, miR186, which was significantly downregulated in the transformed cells and effectively rescued the transformed phenotype. On stimulation of inflammatory cytokines, the activated nuclear factor kappa B (NF-κB)/p65 was able to induce miR186 expression through binding to its promoter in non-transformed cells, whereas this pathway was lost in transformed cells. Interestingly, Twist1, which is a reported downstream target of miR186, was responsible for the loss of NF-κB/p65-miR186 pathway. Twist1 downregulated miR186 expression in a novel negative feedback loop binding to the E-box and simultaneously recruiting Dnmt3a, which facilitated the site-specific CpG methylation of the miR186 promoter, thereby blocked the transcriptional activity of NF-κB/p65 and the responsiveness of miR186 to inflammatory signals. The high level of Twist1 triggered this feedback loop that underlies the epigenetic switch, which was essential for maintaining transformed and advanced PCa state. Finally, our clinical data confirmed that the CpG methylation and miR186 expression levels were closely related with inflammation-associated human PCa progression.