Abstract: Background and purpose: miR-17-92 gene cluster overexpression has been observed in various cancers, such as lung cancer, liver cancer, gastric cancer and prostate cancer. In this study, we established the stable cell line overexpressing miR-17-92 to explore the influence of miR-17-92 on the migration, invasion abilities and cisplatin resistance of the prostate cancer DU145 cells. Methods: miR-17-92 overexpression vectors were constructed. DU145 cells were infected with the viral supernatants produced by Phoenix A packaging system. Real-time fluorescent quantitative polymerase chain reaction (RTFQ-PCR) was conducted to detect the expression level of miR-17-92 in the cells. The migration and invasion abilities were measured by a real-time xCELLigence system. The scratch healing assay was carried out to investigate the migration abilities. The expression of integrin β1 was detected by Western blot, and the activities of matrix metalloprotein-2 (MMP-2) and matrix metalloprotein-9 (MMP-9) were measured by gelatin zymography experiment. The cell growth of the two cell lines after the treatment of cisplatin was detected by a real-time xCELLigence system. The mRNA expression of ERCC1 was measured by RTFQ-PCR. Western blot was conducted to investigate the protein expressions of ERCC1, ERK1/2 and pERK1/2. Results: DU145-miR-17-92 cells migrated faster than DU145-control cells during the 24 h continuous monitoring (P<0.01). The scratch healing assay indicated that DU145-miR-17-92 cells migrated from the edge towards the scratch center faster than DU145-control cells. DU145-miR-17-92 cells invaded through matrigel markedly faster than DU145-control cells (P<0.01). The protein expression level of integrin β1 and the MMP-9 activities in DU145-miR-17-92 cells were increased than those in DU145-control cells. After the treatment of cisplatin, DU145-miR-17-92 cells grew faster than DU145-control cells, presenting cisplatin resistance (P<0.01). The phosphorylation of ERK1/2 in DU145-miR-17-92 cells was constantly at a high level regardless of the treatment of cisplatin. Compared with DU145-control cells, the expression of drug resistance-related gene ERCC1 was dramatically increased in DU145-miR-17-92 cells after the treatment of cisplatin. Conclusion: miR-17- 92 overexpression increases the migration and invasion abilities of the prostate cancer DU145 cells, which is associated with the upregulated expression of integrin β1 and the increased activity of MMP-9. Besides, miR-17-92 overexpression enhances the cisplatin resistance of DU145, which is correlated with the increased phosphorylation level of ERK and the upregulated expression of ERCC1 at both the mRNA and protein levels.

Key words: miR-17-92, Prostate cancer, DU145, Invasion, Migration, Cisplatin