Stimulation of interlukin-8 expression in prostate cancer cell lines by TGF-β1

4532 Human prostate cancer cells and the stroma in the tumor environment produce a number of pro-angiogenic factors. Among them are interleukin (IL)-8 and transforming growth factor (TGF)-β1, both are overexpressed in advanced prostate cancer. Our previous studies suggest that TGF-β1 may contribute to IL-8 regulation in advanced prostate cancer. The purpose of this study was to investigate the effects of TGF-β1 on IL-8 expression in human prostate cancer cells. Three lines of human prostate cancer cell (PC-3MM2, DU-145, and LNCaP-LN3) were used in the present study. IL-8 production was measured by ELISA and IL-8 mRNA levels were determined by real-time reverse transcriptase PCR. We observed that PC-3MM2 cells constitutively express low levels of IL-8, less than 10 ng/105 cells/24 h. Expression of IL-8 at both protein and mRNA levels in PC-3MM2 cells was augmented by TGF-β1 in both dose- and time-dependent manners. TGF-β1 had no direct effects on IL-8 production in LNCaP-LN3 cells. It, however, enhanced IL-1-induced IL-8 production in the cells. In contrast, TGF-β1 did not increase IL-8 expression in DU-145 cells. TGF-β1-induced IL-8 expression in PC-3MM2 cells could be inhibited by the general tyrosine protein kinase inhibitor genistein, the MEK1/2 inhibitor U0126, and the p42/44 mitogen activated protein kinase kinase (MAPKK) inhibitor PD98059, suggesting MAPK activities was required for TGF-β1-induced IL-8 expression. Western blot analysis confirmed that tyrosine-phosphorylatiion of p42/44 MAPK was significantly increased within 30 minutes upon exposure of PC-3MM2 cells to TGF-β1. The above data demonstrate that TGF-β1 upregulates IL-8 expression, through the activation of MAPK pathways in some prostate cancer cells and suggest that it could be one of the factors that regulates IL-8 expression and, hence, angiogenesis in the tumor environment of human prostate cancer.