Role of Wnt/beta-catenin signaling pathway in epithelial-mesenchymal transition of human prostate cancer induced by hypoxia-inducible factor-1alpha.
OBJECTIVE
Epithelial-mesenchymal transition (EMT) is an important process in tumor development, and several studies suggest that the Wnt/beta-catenin signal pathway may play an important role in EMT. However, there is no direct evidence showing that the Wnt/beta-catenin pathway actually determines the EMT induced by an exogenous signal. Our previous research has successfully proved that overexpression of hypoxia-inducible factor-1alpha (HIF-1alpha) could induce EMT in LNCaP cells, but not in PC-3. The present study aims to determine whether the signal of HIF-1alpha for inducing prostate cancer cells to undergo EMT might possibly pass through the Wnt/beta-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/beta-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-1alpha are EMT negative cell lines, whereas LNCaP/HIF-1alpha and IA8 have undergone the EMT process. EMT positive cells (LNCaP/HIF-1alpha 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-1alpha 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 3beta (GSK-3beta) and phospho-GSK-3beta in LNCaP/HIF-1alpha, IA8 and PC-3/HIF-1alpha cells significantly decreased; however, the relative ratios of p-GSK3beta/t-GSK3beta in LNCaP/HIF-1alpha, IA8 and PC-3/HIF-1alpha cells were significantly higher than PC-3 and LNCaP. Consistently, beta-catenin protein expression increased in LNCaP/HIF-1alpha and IA8 cells, but not in PC-3/HIF-1alpha; RT-PCR confirmed these results, except for the enhanced transcription activity of beta-catenin mRNA in PC-3/HIF-1alpha.


CONCLUSIONS
Our data suggests that activation of the Wnt/beta-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-1alpha in prostate cancer cells.
Jiang
Yong-Guang
YG
Department of Urology, Affiliated Beijing Anzhen Hospital of Capital Medical University, Anzhenli Street, Chaoyang District, Beijing, China.
Luo
Yong
Y
He
Da-lin
DL
Li
Xiang
X
Zhang
Lin-lin
LL
Peng
Tao
T
Li
Ming-Chuan
MC
Lin
Yun-Hua
YH
D001672:Biocompatible Materials / Q000494:pharmacology; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D003094:Collagen / Q000494:pharmacology; D004338:Drug Combinations; D004848:Epithelium / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D053538:Keratin-18 / Q000378:metabolism; D007797:Laminin / Q000494:pharmacology; D008297:Male; D008648:Mesoderm / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D011509:Proteoglycans / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D014746:Vimentin / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
D001672:Biocompatible Materials; D015820:Cadherins; D004338:Drug Combinations; D005353:Fibronectins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053538:Keratin-18; D007797:Laminin; D011509:Proteoglycans; D012333:RNA, Messenger; D014746:Vimentin; D051153:Wnt Proteins; D051176:beta Catenin; C059485:matrigel; D003094:Collagen; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3