Plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) play a crucial role in cancer progression. In the present study we examined the regulation of PAI-1 and uPA expressions in normal prostate epithelial cells (PrEC) and the prostate cancer cell lines LNCaP, DU-145, and PC-3. The antigen and mRNA levels of PAI-1 were down-regulated in cancer cells, especially in LNCaP and DU-145. In the presence of proinflammatory cytokines, an increase of PAI-1 mRNA levels was observed in PrEC, LNCaP and PC-3, but not in DU-145 cells. Treatment with demethylating agent, 5-aza-2'-deoxycytidine increased the level of PAI-1 transcript in DU-145 cells and restored the inducing effect of cytokines on PAI-1 expression. An aberrant methylation of PAI-1 promoter in DU-145 and LNCaP cells was shown by methylation-sensitive high resolution melting (MS-HRM) analysis. PAI-1 methylation was also significantly increased in tumor samples (23.2±1.7%) in comparison to adjacent non-tumor tissue (6.0±0.8%). Furthermore, the expression of uPA was increased in high invasive cell lines DU-145 and PC-3 in comparison to PrEC and low invasive LNCaP cells. MS-HRM analysis revealed aberrant methylation of uPA promoter in LNCaP cells, but not in PrEC, DU-145 and PC-3 cells, as well as in normal and prostate cancer tissue samples. In conclusion, the study shows that PAI-1 and uPA expressions were changed in opposite directions in high invasive prostate cancer cell lines resulting in a strong decrease of PAI-1/uPA ratio, which may indicate a shift towards proteolytic activities. Methylation of the PAI-1 gene is suggested as one of the molecular mechanisms involved in the cancer-associated down-regulation of the PAI-1 expression.
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