Impaired expression of connexins, the gap junction subunits that facilitate direct cell-cell communication, have been implicated in prostate cancer growth. To elucidate the crucial role of connexins in prostate cancer progression, we performed a systematic quantitative RT-PCR screening of connexin expression in four representative prostate cancer cell lines across the spectrum of malignancy. Transcripts of several connexin subunits were detected in all four cell lines, and connexin 43 (Cx43) showed marked elevation at both RNA and protein levels in cells with increased metastatic potential. Analysis of gap-junction-mediated intercellular communication revealed homocellular coupling in PC-3 cells, which had the highest Cx43 expression, with minimal coupling in LNCaP cells where Cx43 expression was very low. Treatment with the gap junction inhibitor carbenoxolone or connexin mimetic peptide ACT-1 did not impair cell growth, suggesting that growth is independent of functional gap junctions. PC-3 cells with Cx43 expression reduced by shRNA showed decreased migration in monolayer wound healing assay, as well as decreased transwell invasion capacities when compared to control cells expressing non-targeting shRNA. These results, together with the correlation between Cx43 expression levels and the metastatic capacity of the cell lines, suggest a role of Cx43 in prostate cancer invasion and metastasis.

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