Snail-activated long non-coding RNA PCA3 up-regulates PRKD3 expression by miR-1261 sponging, thereby promotes invasion and migration of prostate cancer cells.

Rapidly accumulated evidence has shown that long non-coding RNA (lncRNAs) disregulation is involved in human tumorigenesis in many cancers, including prostate cancer (PCa). LncRNAs can regulate essential pathways that contribute to tumor initiation and progression with tissue specificity, which suggests that lncRNAs could be valuable biomarkers and therapeutic targets. Prostate cancer antigen 3 (PCA3), also known as differential display code 3 (DD3), is one such lncRNA that maps to chromosome 9q21-22. PCA3 expression is highly specific to PCa. In the present study, the level of PCA3 expression in prostate cancer cells was reduced by small interfering RNA (siRNA). Subsequently, the ability of LNCaP cell proliferation, invasion, and migration of PCa was compromised both in vivo and in vitro with the occurrence of cell autophagy. Recently, a novel regulatory mechanism has been proposed in which RNAs cross talk via competing with the shared microRNAs (miRNAs). In addition, lncRNAs can directly interact with RNA-binding proteins and then bind to the gene promoter region to further regulate gene expression. The proposed competitive endogenous RNAs mediate the bioavailability of miRNAs on their targets, thus imposing another level of post-transcriptional regulation. Here, we demonstrated that binding of Snail to the promoter region of PCA3 could activate the expression of PCA3. Down-regulation of PCA3 by silencing could increase the expression of the miRNA-1261, which then targeted at the PRKD3 gene (protein kinase D3) through competitive sponging. In summary, these results suggest that the transcription factor, Snail, activated the expression of lncRNA PCA3, which could inhibit the translation of PRKD3 protein via competitive miR-1261 sponging, and thus high expression of PRKD3 further promoted invasion and migration of prostate cancer.