Objectives: Epithelial-mesenchymal transition (EMT) is an important process in tumor development, and several studies suggest that the Wnt/b-catenin signal pathway may play an important role in EMT. However, there is no direct evidence showing that the Wnt/b-catenin pathway actually determines the EMT induced by an exogenous signal. Our previous research has successfully proved that overexpression of hypoxiainducible factor-1a (HIF-1a) could induce EMT in LNCaP cells, but not in PC-3. The present study aims to determine whether the signal of HIF-1a for inducing prostate cancer cells to undergo EMT might possibly pass through the Wnt/b-catenin pathway. Methods: Epithelial-mesenchymal transition associated proteins were detected in several human prostate carcinoma cell lines by Western blot, and then we distinguished the EMT positive cell lines from the EMT negative cell lines. Furthermore, we evaluated the possible correlation between potency of invasiveness and proliferation among these cell lines with different characteristics of EMT using Matrigel transwell and thiazolyl blue tetrazolium bromide (MTT) assays. Finally, the different expression of some critical proteins and genes in Wnt/b-catenin signaling pathway were analyzed by Western blot and reverse transcription-polymerase chain reaction (RT-PCR) in these cells with different characteristics of EMT. Results: Among several prostate cancer cell lines, PC-3, LNCaP and PC-3/HIF-1a are EMT negative cell lines, whereas LNCaP/HIF-1a and IA8 have undergone the EMT process. EMT positive cells (LNCaP/HIF-1a and IA8) exhibit much stronger potency of invasiveness and proliferation than those of PC-3 and LNCaP, which belong to EMT negative cells. Interestingly, although PC-3/HIF-1a had not completed the EMT process, it still displayed stronger potency of invasion and proliferation, resembling EMT positive cells. The protein expression level of total glycogensynthase kinase 3b (GSK-3b) and phospho-GSK-3b in LNCaP/HIF-1a, IA8 and PC-3/HIF-1a cells significantly decreased; however, the relative ratios of p-GSK3b/t-GSK3b in LNCaP/HIF-1a, IA8 and PC-3/HIF-1a cells were significantly higher than PC-3 and LNCaP. Consistently, b-catenin protein expression increased in LNCaP/HIF-1a and IA8 cells, but not in PC-3/HIF-1a; RT-PCR confirmed these results, except for the enhanced transcription activity of b-catenin mRNA in PC-3/HIF-1a. Conclusion: Our data suggests that activation of the Wnt/b-catenin signaling pathway correlates with the characteristic of EMT and potency of invasiveness and proliferation. This may be the critical factor that directly controls the process of EMT induced by HIF-1a in prostate cancer cells.

Some genes involved in complex human diseases are particularly vulnerable to genetic variations such as single nucleotide polymorphism, copy number variations, and mutations. For example, Ras mutations account for over 30% of all human cancers. Additionally, there are some genes that can display different variations with functional impact in different diseases that are unrelated. One such gene stands out: δ-catenin/NPRAP/Neurojungin with gene designation as CTNND2 on chromosome 5p15.2. Recent advances in genome wide association as well as molecular biology approaches have uncovered striking involvement of δ-catenin gene variations linked to complex human disorders. These disorders include cancer, bipolar disorder, schizophrenia, autism, Cri-du-chat syndrome, myopia, cortical cataract-linked Alzheimer’s disease, and infectious diseases. This list has rapidly grown longer in recent years, underscoring the pivotal roles of δ-catenin in critical human diseases. δ-Catenin is an adhesive junction-associated protein in the delta subfamily of the β-catenin superfamily. δ-Catenin functions in Wnt signaling to regulate gene expression and modulate Rho GTPases of the Ras superfamily in cytoskeletal reorganization. δ-Catenin likely lies where Wnt signaling meets Rho GTPases and is a unique and vulnerable common target for mutagenesis in different human diseases.