Cytotoxic Effects and Androgen Receptor Expression According to Concentrations of Genistein with Silencing Cyclooxygenase–2 Gene Expression in Prostate Cancer Cells

COX–2 has major roles in inflammatory reaction, and COX–2 inhibitor and genistein have a chemopreventive effect on some cancers such as colorectal, breast, and prostate cancer (PCa). The aims of this study was to investigate combined effect of COX–2 inhibition and genistein treatment. To address this issue, we tested the degree of cell survival and the changes of androgen receptor in PCa cells with silencing of COX–2 according to concentrations of genistein. DU–145 PCa cells were transfected with COX–2 siRNA. The mRNA expressions of androgen receptor and caspase–3 were detected using reverse transcription polymerase chain reaction in the cells with or without COX–2 siRNA transfection. Immunofluorescent staining was performed on PCa cell with COX–2, androgen receptor and caspase–3 antibody and analyzed with confocal microscopy and image analyzer. Cell cytotoxicity according to concentrations of genistein was analyzed with MTT assay. The mRNA expression of AR was down–regulated in DU–145 cell line according to concentration of genistein, but caspase–3 expression showed up–regulated pattern in increasing the dosage of genistein. COX–2 siRNA (+) group was stronger mRNA expression of caspase–3 and weaker mRNA expression of AR than COX–2 siRNA (–) group. The immunofluorescent staining results were similar with those of mRNA expression. The results of cell survival showed that COX–2 siRNA (+) group with genistein was more cytotoxic compared to COX–2 siRNA (–) group (Repeated Measured ANOVA, p=0.004). There was significant cytotoxic effects in COX–2 siRNA (+) group between 10μM and 50μM of concentration of genistein compared to COX–2 siRNA (–) group (p<0.0001). The effect of genistein and silencing of COX–2 shows that it reduced AR and increased caspase–3 in PCa cells. These results suggest that genistein and silencing of COX–2 might be a role in the inhibition of cell proliferation and induction of apoptosis