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.     

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.     

The intratumoral distribution of nuclear β‐catenin is a prognostic marker in colon cancer

BACKGROUND:

Most colon cancers harbor mutations of APC or β‐catenin, both of which may lead to nuclear β‐catenin accumulation in the tumor cells and constitutively activated expression of its target genes. In many colon cancers, however, nuclear β‐catenin accumulation is heterogeneous throughout the tumor and often confined to the tumor margin. Herein, the authors investigated whether the intratumoral distribution of nuclear β‐catenin can serve as a prognostic marker for survival and tumor progression of stage IIA colon cancer patients.

METHODS:

In total, 142 patients with primarily resected, moderately differentiated stage IIA colon cancer were included in this study. The patterning of nuclear β‐catenin expression was evaluated on immunohistochemically stained whole tissue sections of the tumors and was correlated with cancer‐specific survival and disease‐free survival using univariate and multivariate statistical analyses.

RESULTS:

Four distinct patterns of nuclear β‐catenin expression were identified, and 2 main categories comprising tumors with or without intratumoral regulation of nuclear β‐catenin were distinguished. Moreover, the results demonstrated that the patterning, and especially the regulation or absence of regulation of nuclear β‐catenin expression, was a strong predictive marker of patient survival and tumor progression.

CONCLUSIONS:

The current results indicated that the distribution of nuclear β‐catenin expression can be used as a good prognostic marker in patients with stage IIA colon cancer. Thus, the evaluation of nuclear β‐catenin may help to identify patients who will have a shorter than average survival and patients with a greater risk of disease progression who may be considered for adjuvant therapeutic modalities and intensified clinical aftercare in the future. Cancer 2009. © 2009 American Cancer Society.     

P7TP3 inhibits tumor development,migration, invasion and adhesion of liver cancer through the Wnt/β‐catenin signaling pathway

The effect of hepatitis C virus p7 trans‐regulated protein 3 (P7TP3) in the development of hepatocellular carcinoma (HCC) is still unknown. The present study aimed to investigate the role and mechanism of P7TP3 in HCC. P7TP3 was significantly decreased in HCC tissues when compared with corresponding liver tissues immediately around the tumor (LAT) from seven HCC patients. Fewer and smaller colonies originated from HepG2‐P7TP3 cells when compared to HepG2‐NC cells. Overexpression of P7TP3 in HepG2 cells significantly repressed the growth of HCC xenografts in nude mice. Furthermore, wound‐healing tests, Transwell assays, Matrigel Transwell assays, adhesion assays, CCK‐8 assays, flow cytometry and western blotting analysis showed that P7TP3 protein expression inhibited migration, invasion, adhesion, proliferation and cell cycle progression in HCC cell lines. Moreover, P7TP3 suppressed the activity of the Wnt/β‐catenin signaling pathway, and was restored by Wnt3a, which is an activator of the Wnt/β‐catenin signaling pathway. Consistently, β‐catenin was highly expressed by P7TP3 silencing, and restored by XAV939, an inhibitor of the Wnt/β‐catenin signaling pathway. Finally, microRNA (miR)‐182‐5p suppressed the expression of target gene P7TP3 by directly interacting with the 3′‐UTR region. Taken together, P7TP3, the direct target gene of miR‐182‐5p, inhibited HCC by regulating migration, invasion, adhesion, proliferation and cell cycle progression of liver cancer cell through the Wnt/β‐catenin signaling pathway. These findings provide strong evidence that P7TP3 functions as a new promising tumor suppressor in HCC.     

抑癌基因甲基化与胃癌研究进展

DNA甲基化是基因表达调控的一种方式，抑癌基因启动子高甲基化可以使其表达受抑，这与肿瘤的发生关系密切。胃癌的发生是由多因素多基因多阶段异常累计的结果，其中抑癌基因甲基化与胃癌的发生具有重要的关系。     

Cancer‐associated fibroblast‐derived Lumican promotes gastric cancer progression via the integrin β1‐FAK signaling pathway

Gastric cancer (GC) is one of the most frequent malignant tumors worldwide and is associated with high invasiveness, high metastasis and poor prognosis. Cancer‐associated fibroblasts (CAFs), residing around tumor cells in tumor stroma, are important modifiers of tumor initiation and progression. However, the molecular mechanisms by which CAF's modulate tumor development have yet not to be characterized in GC. Here we performed tissue assay analyses identifying that Lumican, an extracellular matrix protein, is highly expressed in human gastric CAFs and its expression is positively associated with depth of invasion, lymph node metastasis, TNM stage and poor survival rate of GC. Functional studies revealed that integrin β1‐FAK signaling pathways mediate the promoting effect of Lumican on GC cell proliferation, migration and invasion in vitro. In accordance with these observations, in GC cells co‐cultured with CAFs in which Lumican had been knocked down, decreased gastric tumor growth and metastasis in vivo was apparent. In summary, CAF‐derived Lumican contributes to tumorigenesis and metastasis of GC by activating the integrin β1‐FAK signaling pathway.     

Genome‐wide identification of Epstein‐Barr virus–driven promoter methylation profiles of human genes in gastric cancer cells

BACKGROUND:

Aberrant methylation of tumor‐related genes has been reported in Epstein‐Barr virus (EBV)‐associated gastric cancers. This study sought to profile EBV‐driven hypermethylation in EBV‐infected cells.

METHODS:

The EBV‐positive AGS gastric cancer cell line (AGS‐EBV) and EBV‐negative AGS cells were used in this study. DNA methyltransferase‐3b (DNMT3b) activity was assessed by EpiQuick activity assay, and genome‐wide DNA methylation profiles were assessed by methyl‐DNA immunoprecipitation microarray assay.

RESULTS:

EBV infection was confirmed in AGS‐EBV cells by EBV‐encoded RNA in situ hybridization. Expression and activity of DNA methyltransferase‐3b (DNMT3b) was significantly increased in AGS‐EBV compared to AGS. Ectopic expression of LMP2A (latent membrane protein 2A) in AGS increased activity of DNMT3b. A total of 1065 genes were differentially methylated by EBV infection (fold‐changes ≥ 2, P < .05) in AGS‐EBV compared to AGS cells. The majority of the differentially methylated genes (83.2%, 886 of 1065 genes) had cytosine‐guanine dinucleotide (CpG) hypermethylation in AGS‐EBV (fold‐changes 2.43～65.2) versus that found in AGS cells. Gene ontology analysis revealed that hypermethylated genes were enriched in the important cancer pathways (≥ 10 genes each, P ≤ .05) including mitogen‐activated protein kinase signaling, cell adhesion molecules, wnt signaling pathway, and so forth. Six novel hypermethylated candidates (IL15RA, REC8, SSTR1, EPHB6, MDGA2, and SCARF2) were further validated. Higher levels of DNA methylation were confirmed for all these genes in AGS‐EBV cells by bisulfite genomic sequencing. Furthermore, these candidates were silenced or down‐regulated in AGS‐EBV cells, but can be restored by demethylation treatment.

CONCLUSIONS:

EBV infection in AGS cells induced aberrant CpG hypermethylation of 886 genes involving in important cancer‐related pathways. Induction of promoter methylation by EBV is regulated by up‐regulation of DNMT3b through LMP2A. Cancer 2013. © 2012 American Cancer Society.