HBx mutations promote hepatoma cell migration through the Wnt/β‐catenin signaling pathway

HBx mutations (T1753V, A1762T, G1764A, and T1768A) are frequently observed in hepatitis B virus (HBV)‐related hepatocellular carcinoma (HCC). Aberrant activation of the Wnt/β‐catenin signaling pathway is involved in the development of HCC. However, activation of the Wnt/β‐catenin signaling pathway by HBx mutants has not been studied in hepatoma cells or HBV‐associated HCC samples. In this study, we examined the effects of HBx mutants on the migration and proliferation of HCC cells and evaluated the activation of Wnt/β‐catenin signaling in HBx‐transfected HCC cells and HBV‐related HCC tissues. We found that HBx mutants (T, A, TA, and Combo) promoted the migration and proliferation of hepatoma cells. The HBx Combo mutant potentiated TOP‐luc activity and increased nuclear translocation of β‐catenin. Moreover, the HBx Combo mutant increased and stabilized β‐catenin levels through inactivation of glycogen synthase kinase‐3β, resulting in upregulation of downstream target genes such as c‐Myc, CTGF, and WISP2. Enhanced activation of Wnt/β‐catenin was found in HCC tissues with HBx TA and Combo mutations. Knockdown of β‐catenin effectively abrogated cell migration and proliferation stimulated by the HBx TA and Combo mutants. Our results indicate that HBx mutants, especially the Combo mutant, allow constitutive activation of the Wnt signaling pathway and may play a pivotal role in HBV‐associated hepatocarcinogenesis.     

The dual role of the novel Wnt receptor tyrosine kinase,ROR2, in human carcinogenesis

The Wnt signaling pathway is involved in the development and progression of many human cancers, yet attempts to target the pathway therapeutically have been disappointing to date. The recent discovery that the ROR2 receptor tyrosine kinase (RTK) is a novel Wnt receptor provides the potential to target the non‐canonical Wnt pathway for cancer treatments. As a member of the RTK superfamily of surface receptors ROR2 appears to possess dual roles as a tumor suppressor or activator depending on tumor type. This review will explore the dual role of ROR2 in tumorigenesis and provide an up to date analysis of current literature in this rapidly expanding field.     

Context‐dependent activation of Wnt signaling by tumor suppressor RUNX3 in gastric cancer cells

RUNX3 is a tumor suppressor for a variety of cancers. RUNX3 suppresses the canonical Wnt signaling pathway by binding to the TCF4/β‐catenin complex, resulting in the inhibition of binding of the complex to the Wnt target gene promoter. Here, we confirmed that RUNX3 suppressed Wnt signaling activity in several gastric cancer cell lines; however, we found that RUNX3 increased the Wnt signaling activity in KatoIII and SNU668 gastric cancer cells. Notably, RUNX3 expression increased the ratio of the Wnt signaling‐high population in the KatoIII cells. although the maximum Wnt activation level of individual cells was similar to that in the control. As found previously, RUNX3 also binds to TCF4 and β‐catenin in KatoIII cells, suggesting that these molecules form a ternary complex. Moreover, the ChIP analyses revealed that TCF4, β‐catenin and RUNX3 bind the promoter region of the Wnt target genes, Axin2 and c‐Myc, and the occupancy of TCF4 and β‐catenin in these promoter regions is increased by the RUNX3 expression. These results suggest that RUNX3 stabilizes the TCF4/β‐catenin complex on the Wnt target gene promoter in KatoIII cells, leading to activation of Wnt signaling. Although RUNX3 increased the Wnt signaling activity, its expression resulted in suppression of tumorigenesis of KatoIII cells, indicating that RUNX3 plays a tumor‐suppressing role in KatoIII cells through a Wnt‐independent mechanism. These results indicate that RUNX3 can either suppress or activate the Wnt signaling pathway through its binding to the TCF4/β‐catenin complex by cell context‐dependent mechanisms.     

Delphinidin suppresses breast carcinogenesis through the HOTAIR/microRNA‐34a axis

Delphinidin, one of the main anthocyanidins, has potent anti‐cancer properties. In this study, we investigated the effect of delphinidin on 1‐methyl‐1‐nitrosourea (MNU)‐induced breast carcinogenesis on rats and the mechanism of delphinidin via negative regulation of the HOTAIR/microRNA‐34a axis. We found administration of delphinidin could effectively suppress MNU‐induced mammal breast carcinogenesis. Delphinidin downregulated the level of HOTAIR and upregulated miR‐34a in breast carcinogenesis. Western blot analysis confirmed that delphinidin treatment can significantly decrease the expression of β‐catenin, glycogen synthase kinase‐3β (Gsk3β), c‐Myc, cyclin‐D1, and matrix metalloproteinase‐7(MMP‐7) expression in breast cancer cells, and inhibition of miR‐34a significantly reduced the effect of delphinidin on c‐Myc, cyclin‐D1, and MMP‐7. HOTAIR overexpression also blocked the effect of delphinidin on miR‐34a and the Wnt/β‐catenin signaling pathway in MDA‐MB‐231 cells. RNA immunoprecipitation (RIP) assay and chromatin immunoprecipitation (ChIP) assay results showed that delphinidin upregulated miR‐34a by inhibiting HOTAIR, coupled with enhancement of the zeste homolog 2 (EZH2) and histone H3 Lys27 trimethylation (H3K27me3). This study indicated that delphinidin may potentially suppress breast carcinogenesis and exert its anti‐cancer effect through the HOTAIR/miR‐34a axis. These findings provided new evidence for the use of delphinidin in preventing breast carcinogenesis.     

Epigenetic silencing of SFRP1 and SFRP5 by hepatitis B virus X protein enhances hepatoma cell tumorigenicity through Wnt signaling pathway

Secreted frizzled‐related proteins (SFRPs) are antagonists of the Wnt signaling pathway whose epigenetic downregulation have been shown to be involved in hepatocarcinogenesis. However, dysregulation of SFRPs induced by hepatitis B virus (HBV) X protein (HBx) has never been studied in HBV‐related hepatocellular carcinoma (HBV‐HCC). In this study, we sought to determine the clinical significance and underlying mechanism of HBx‐induced SFRPs dysregulation in hepatoma cells and HBV‐HCC patients. Our results showed that SFRP1 and SFRP5 expression were dramatically decreased by HBx in hepatoma cells. The repressed expression in hepatoma cells was partially rescued by a DNA methylation inhibitor and synergistically increased by a combination treatment with a histone deacetyltransferases inhibitor. In addition, we identified that SFRP1 and SFRP5 promoters were hypermethylated in both HBx‐expressing hepatoma cells and HBV‐HCC tissues. Downregulation of SFRP1 and SFRP5 in HBV‐HCC tissues was significantly correlated with overexpression of DNA methyltransferase 1 (DNMT1) and poor tumor differentiation. HBx facilitated the binding of DNMT1 and DNMT3A to SFRP1 and SFRP5 promoters, and resulted in epigenetic silencing of SFRP1 and SFRP5. Moreover, overexpression of SFRP1, SFRP5 or RNA interference mediated silencing of DNMT1 inactivated the Wnt signaling pathway and decreased the expression levels of Wnt target genes c‐Myc and CyclinD1, thus impeding HCC growth in vitro and in vivo, and regressing HBx‐induced epithelial–mesenchymal transition (EMT). Our findings strongly suggest that epigenetic silencing of SFRP1 and SFRP5 by HBx allows constitutive activation of Wnt signaling pathway and hence contributes to hepatocarcinogenesis.     

HBO1 promotes cell proliferation in bladder cancer via activation of Wnt/β‐catenin signaling

Histone acetyltransferase binding to ORC1 (HBO1), a histone acetyltransferase, was recently identified as an oncoprotein; however, its role in bladder cancer remains unknown. In this study, we showed that HBO1 was highly expressed at both the mRNA and the protein levels in bladder cancer. HBO1 expression was associated with the clinical features of human bladder cancer, including tumor size (P = 0.018) and T (P = 0.007) classifications. Patients with higher HBO1 expression had shorter recurrence‐free survival time, whereas patients with lower HBO1 expression had better survival time. Moreover, we found that ectopic overexpression of HBO1 promoted, whereas HBO1 silencing inhibited tumor growth in bladder cancer cells both in vitro and in vivo. We further demonstrated that upregulation of HBO1 activated the Wnt/β‐catenin signaling pathway and led to nuclear localization of β‐catenin and upregulation of downstream targets of of Wnt/β‐catenin signaling. These findings suggest that HBO1 plays a key role in the progression of bladder cancer via the Wnt/β‐catenin pathway, and may serve as a potential therapeutic target for the treatment of bladder cancer.     

A mouse model for endometrioid ovarian cancer arising from the distal oviduct

Ovarian cancer is the deadliest gynecological malignancy in Western countries. Early detection, however, is hampered by the fact that the origin of ovarian cancer remains unclear. Knowing that in a high percentage of endometrioid ovarian cancers Wnt/β‐catenin signaling is activated, and in view of the hypothesis that ovarian cancer may originate from the distal oviduct, we studied mice in which Wnt/β‐catenin signaling was activated in Müllerian duct‐derived tissues. Conditional adenomatous polyposis coli (Apc) knockout mice were used to study the activation of Wnt/β‐catenin signaling in Müllerian duct‐derived organs. These Pgr^Cre/+;Apc^ex15lox/lox mice (n = 44) were sacrificed at 10, 20, 40 and 80 weeks and uterus, oviduct, ovaries and surrounding fat tissues were assessed using immunohistochemistry. Using nuclear β‐catenin staining, Wnt/β‐catenin signaling activation was confirmed in the entire epithelium of the adult Müllerian duct (fimbriae, oviduct and endometrium), but was absent in ovarian surface epithelium cells (OSEs). Besides endometrial hyperplasia, in 87.2% of mice intraepithelial lesions of the distal oviduct were found, whereas OSEs remained unaffected. In addition, 62.5% of mice developed tumors in the distal and fimbrial part of the oviduct. In the ovaries, mainly at young age, in 16.3% of mice, simple epithelial cysts were noted, which developed further into endometrioid ovarian tumors, resembling human endometrioid ovarian cancer (27.9% of mice). Next to this, locoregional growth in the utero‐ovarian ligament was also shown. Here, for the first time, mutations (activation of Wnt/β‐catenin) in the distal oviduct result in precursor lesions that develop into ovarian tumors, resembling human endometrioid ovarian cancer.