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Increased expression of E2F1 has been reported to be associated with tumor growth and cell survival of prostate cancer (PCa). However, its roles and mechanisms on PCa have not been fully elucidated. The present study found that E2F1 overexpression in PCa tissues was significantly associated with high Gleason score (P=0.01) and advanced pathological stage (P=0.02). In addition, PCa patients with high E2F1 expression more frequently had shorter biochemical recurrence-free survival (P=0.047) than those with low E2F1 expression. Then, we confirmed that the knock-down of E2F1 expression was able to inhibit cell cycle progression, invasion and migration of PCa cell lines in vitro, along with tumor xenograft growth and epithelial-to-mesenchymal transition (EMT) in vivo. Moreover, we identified CD147 as a novel interaction partner for E2F1 through bio-informatic binding site prediction, combined with chromatin immunoprecipitation-PCR (ChIP-PCR) and western blot analysis. Taken together, our data delineate an as yet unrecognized function of E2F1 as enhancer of tumor invasion and migration of PCa via regulating the expression of CD147 in PCa. Importantly, E2F1 may function as a biomarker that can differentiate patients with biochemical recurrent and non-biochemical recurrent disease following radical prostatectomy, highlighting its potential as a therapeutic target.

Our previous study revealed the potential role of CD147 in human prostate cancer (PCa). Here, we investigated the CD147 promoter methylation status and the correlation with tumorigenicity in human PCa. CD147 mRNA and protein expression levels were both significantly higher in the 4 PCa cell lines, than in the 2 non-tumorigenic benign human prostatic epithelial cell lines (all P<0.01). We showed hypomethylation of promoter regions of CD147 in PCa cell lines with significant CD147 expression as compared to non-tumorigenic benign human prostatic epithelial cell lines slowly expressing CD147. Additionally, the treatment of methylated cell lines with 5-aza-2'-deoxycytidine increased CD147 expression significantly in low-expressing cell lines and also activated the expression of matrix metalloproteinase (MMP)-2, which may be one of the most important downstream targets of CD147. Furthermore, PCa tissues displayed decreased DNA methylation in the promoter region of CD147 compared to the corresponding non-cancerous prostate tissues, and methylation intensity correlated inversely with the CD147 mRNA levels. There was a significant negative correlation between CD147 mRNA levels and the number of methylated sites in PCa tissues (r=-0.467, P<0.01). In conclusion, our data offer convincing evidence for the first time that the DNA promoter hypomethylation of CD147 may be one of the regulatory mechanisms involved in the cancer-related overexpression of CD147 and may play a crucial role in the tumorigenesis of PCa.