miR-19a and miR-421 target PCA3 long non-coding RNA and restore PRUNE2 tumor suppressor activity in prostate cancer

Prostate cancer antigen 3 (PCA3) is the most promising diagnostic biomarker for the differential diagnosis of prostate cancer identified to date. As a dominant-negative oncogene, PCA3 negatively regulates the expression of tumor suppressor PRUNE2 (a human homolog of the Drosophila prune gene) gene. Although interaction between PCA3-PRUNE2 was clearly reported, the precise mechanism how PCA3 is upregulated in prostate cancer remained highly elusive. Accordingly, here we aimed demonstrate the role of microRNAs in PCA3 upregulation and interplay between these miRNAs and PCA3-PRUNE2 axis.

We evaluated expression of PCA3, PRUNE2 and miRNAs by quantitative reverse transcription polymerase chain reaction. Overexpression and silencing of miRNAs were achieved by synthetic miRNA mimics and inhibitors, respectively. Colony formation, migration, apoptosis, and cell cycle assays were performed to reveal the effects of miRNA modulation. We identified that PCA3 expression was significantly downregulated in both prostate cancer tissues and cells and inversely correlated with the expressions of miR-19a and miR-421. Restoring the functions of miR-19a and miR-421 by miRNA mimics significantly downregulated the expression of PCA3 and promoted apoptosis and cell cycle blockade and interfered with the proliferation and migration in prostate cancer cells. Conversely, silencing the expressions of these miRNAs yielded the opposite effect.

Collectively, our results uncover a previously unrecognized novel mechanism on PCA3 upregulation in prostate cancer and proved that miR-19a and miR-421 might be responsible for the increased expression of PCA3, indicating that both miRNAs might be novel candidates for prostate cancer diagnosis and therapy.