[Role of beta-catenin signaling pathway in EMT of human prostate cancer induced by HIF-1alpha].

OBJECTIVE: Epithelial-mesenchymal transition (EMT) is an important process in tumor development. Several studies suggest that the beta-catenin signal pathway may play an important role in EMT. However, there is no direct evidence showing that this pathway actually determines the EMT induced by exogenous signal. Our previous study has successfully proved that over-expression of HIF-1alpha could induce EMT in LNCaP cells, but not in PC-3. So the present study was intended to indicate that the signal of HIF-1alpha for inducing prostate cancer cell to undergo EMT might pass through the beta-catenin pathway.

METHODS: Firstly, we analyzed the expression of HIF-1alpha and its target proteins in LNCaP/HIF1alpha and PC-3/HIF1alpha by Western blot. And then EMT-associated proteins were detected by Western blot. Furthermore the potency of invasiveness and proliferation of several cell lines were evaluated by transwell and MTT assay. Lastly the expressions of beta-catenin and GSK-3beta in these cells were analyzed by Western blot and RT-PCR.

RESULTS: HIF-1alpha, Glut-1 and VEGF were highly expressed in LNCaP/HIF1alpha and PC-3/HIF1alpha. And PC-3, LNCaP and PC-3/HIF1alpha were EMT-negative cell lines whereas LNCaP/HIF1alpha and IA8 had undergone EMT process. LNCaP/HIF1alpha, IA8 and PC-3/HIF1alpha exhibited a much stronger potency of invasiveness and proliferation than those of PC-3 and LNCaP. The protein levels of total GSK-3beta and phospho-GSK-3beta in LNCaP/HIF1alpha, IA8 and PC-3/HIF1alpha cells significantly decreased; however, the relative ratios of p-GSK3beta/t-GSK3beta increased. Consistently, beta-catenin protein expression increased in LNCaP/HIF1alpha and IA8 cells, but not in PC-3/HIF1alpha; RT-PCR confirmed these results, except for an enhanced transcription activity of beta-catenin mRNA in PC-3/HIF1alpha.

CONCLUSION: The activation of the beta-catenin signaling pathway correlates with the characteristic of EMT and potency of invasiveness and proliferation. And it may be one critical factor directly controlling the process of EMT induced by HIF-1alpha in prostate cancer.