Wnt/β-catenin signaling enhances hypoxia-induced epithelial–mesenchymal transition in hepatocellular carcinoma via crosstalk with hif-1α signaling

Abstract

Epithelial-mesenchymal transition (EMT) is a critical process for tumor invasion and metastasis. Hypoxia may induce EMT, and upregulated β-catenin expression has been found in various tumors. In this study, we investigate the role of β-catenin in hypoxia-induced EMT in hepatocellular carcinoma (HCC). Induction of EMT in HCC cell lines by hypoxia was confirmed by altered morphology, expression change of EMT-associated markers and enhanced invasion capacity. We showed that hypoxia-induced EMT could be enhanced by addition of recombinant Wnt3a while it was repressed by β-catenin small interfering RNA. An interaction between β-catenin and hypoxia-induced factor-1α (hif-1α) was found, and an underlying competition for β-catenin between hif-1α and T-cell factor-4 was implied. Notably, increased hif-1α activity was accompanied with more significant EMT features. We also showed that the pro-EMT effect of β-catenin in hypoxia was deprived in the absence of hif-1α. Moreover, β-catenin was found to be responsible for the maintenance of viability and proliferation for tumor cells undergoing hypoxia. We further showed a correlation between hif-1α and β-catenin expression, and corresponding expression of EMT-associated markers in human HCC tissues. Our results suggest that Wnt/β-catenin signaling enhances hypoxia-induced EMT in HCC by increasing the EMT-associated activity of hif-1α and preventing tumor cell death.

PKM2 Regulates Hepatocellular Carcinoma Cell Epithelial-mesenchymal Transition and Migration upon EGFR Activation

“…Besides, HGF/c-met pathway was found to promote EMT via upregulation of cyclooxygenase 2 and PI3K (Pan et al, 2010). Recently, it has been reported that Wnt/β-catenin signaling could enhance hypoxia-induced EMT in HCC via crosstalk with hypoxia-inducible factor-1α (HIF-1α) (Zhang et al, 2013). In the present study, we demonstrated that EGF induced EMT by activating PI3K and ERK pathways in HCC cell lines.…”

“…Here we observed its role in EGFinduced EMT and cell motility in HCC cells. Recent clinical investigations have demonstrated that PKM2 is up-regulated in colorectal cancer and correlated with colon cancer metastasis (Zhou et al, 2012a), but the mechanism is unknown. The findings from this study and others strongly suggest that PKM2 plays an important role not only in cell proliferation but also in EMT/cell motility, contributing to tumor metastasis.…”

“…Therefore, β-catenin, HIF-1α and PKM2 could be key molecules involved in the EMT process in HCC. Interestingly, there have been many reports demonstrating the interactions between these molecules, which were important for tumor proliferation, invasion and progression (Luo et al, 2011a;Yang et al, 2011;Zhang et al, 2013). It could be postulated that the EMT process induced by different factors in HCC could be attributed to some common mechanisms involving β-catenin, HIF-1α and PKM2 simultaneously.…”

“…The qRT-PCR was performed using IQTM SYBR Green supermix and the iQ5 real-time detection system (Bio-Rad Laboratories, Hercules, CA, USA). Primers used for qRT-PCR were as described in the following (Zhang et al, 2013): E-cadherin: (forward) 5'-TCCCATCAGCTGCCCAGAAA-3', (reverse) 3'-TGACTCCTGTGTTCCTGTTA-5'; Vimentin: (forward) 5'-ATGAGTACCGGAGACAGGTGCAGA-3'; (reverse) 5'-ATAGCAGCTTCAACGGCAAAGTTCA-3'; Snail: (forward) 5'-TTCTTCTGCGCTACTGCTGCG-3'; (reverse) 3'-GGGCAGGTATGGAGAGGAAGA-5'; GAPDH: (forward) 5'-TGGTATCGTGGAAGGACTCAT GAC-3'; (reverse) 3'-ATGCCAGTGAGCTTCCCGTTCA GC-5'.…”

Ursolic acid sensitized colon cancer cells to chemotherapy under hypoxia by inhibiting MDR1 through HIF-1α

“…There is a general understanding that the hypoxic microenvironment can promote tumor progression as well as drug resistance (Selvakumaran et al, 2013;Zhang et al, 2013;Liu et al, 2015). One of the first reported molecular mechanisms explaining the contribution of hypoxia to drug resistance was the finding that the hypoxia-inducible factor 1α (HIF-1α) was able to activate the multidrug resistance gene 1 (MDR1), which encodes for the P-glycoprotein (P-gp) that decreases intracellular drug concentration by acting as a drug efflux pump (Bellamy, 1996;Chen et al, 2014).…”