Expression patterns of the tumor suppressor PDCD4 and correlation with β-catenin expression in gastric cancers

The expression patterns of PDCD4, a tumor suppressor, and β-catenin were immunohistologically investigated in gastric carcinoma tissues. In normal gastric tissues, PDCD4 was strongly expressed in the cell nuclei, but weakly expressed in the cytoplasm. In gastric adenocarcinoma tissues, nuclear PDCD4 expression was decreased, while cytoplasmic PDCD4 expression was unchanged or somewhat increased. In gastric signet ring cell carcinoma tissues, PDCD4 expression patterns were different from the expression patterns of the adenocarcinoma tissues, and PDCD4 was localized in the nuclei of the carcinoma cells as a belt in the middle of the epithelial layer. The nuclear localization of PDCD4 in the adenocarcinoma tissues was correlated with the membrane localization of β-catenin, the activation of which stimulates invasion of colon cancer cells. PDCD4 expression was correlated with β-catenin expression in gastric carcinoma cell lines, but not with E-cadherin, as the binding partner in the cell membrane.     

Regulation of β-catenin by t-DARPP in upper gastrointestinal cancer cells

Background  

Truncated dopamine and cyclic-AMP-regulated phosphoprotein (t-DARPP) is frequently overexpressed in gastrointestinal malignancies. In this study, we examined the role of t-DARPP in regulating β-catenin.     

Regulation of cancer progression by β-endorphin neuron

It is becoming increasingly clear that stressful life events can affect cancer growth and metastasis by modulating nervous, endocrine, and immune systems. The purpose of this review is to briefly describe the process by which stress may potentiate carcinogenesis and how reducing body stress may prevent cancer growth and progression. The opioid peptide β-endorphin plays a critical role in bringing the stress axis to a state of homeostasis. We have recently shown that enhancement of endogenous levels of β-endorphin in the hypothalamus via β-endorphin neuron transplantation suppresses stress response, promotes immune function, and reduces the incidence of cancer in rat models of prostate and breast cancers. The cancer-preventive effect of β-endorphin is mediated through the suppression of sympathetic neuronal function, which results in increased peripheral natural killer cell and macrophage activities, elevated levels of anti-inflammatory cytokines, and reduced levels of inflammatory cytokines. β-endorphin inhibition of tumor progression also involves alteration in the tumor microenvironment, possibly because of suppression of catecholamine and inflammatory cytokine production, which are known to alter DNA repair, cell-matrix attachments, angiogenic process, and epithelial-mesenchymal transition. Thus, β-endorphin cell therapy may offer some therapeutic value in cancer prevention.     

SOX10, a novel HMG-box-containing tumor suppressor,inhibits growth and metastasis of digestive cancers by suppressing the Wnt/β-catenin pathway

SOX10 was identified as a methylated gene in our previous cancer methylome study. Here we further analyzed its epigenetic inactivation, biological functions and related cell signaling in digestive cancers (colorectal, gastric and esophageal cancers) in detail. SOX10 expression was decreased in multiple digestive cancer cell lines as well as primary tumors due to its promoter methylation. Pharmacologic or genetic demethylation reversed SOX10 silencing. Ectopic expression of SOX10in SOX10-deficient cancer cells inhibits their proliferation, tumorigenicity, and metastatic potentials in vitro and in vivo. SOX10 also suppressed the epithelial to mesenchymal transition (EMT) and stemness properties of digestive tumor cells. Mechanistically, SOX10 competes with TCF4 to bind β-catenin and transrepresses its downstream target genes via its own DNA-binding property. SOX10 mutations that disrupt the SOX10-β-catenin interaction partially prevented tumor suppression. SOX10is thus a commonly inactivated tumor suppressor that antagonizes Wnt/β-catenin signaling in cancer cells from different digestive tissues.     

SENP2 Regulates Hepatocellular Carcinoma Cell Growth by Modulating the Stability of β-catenin

SUMOylation has emerged as an important post-translational modification that modulates the localization,stability and activity of a broad spectrum of proteins. A dynamic process, it can be reversed by a family of SUMOspecificproteases (SENPs). However, the biological roles of SENPs in mammalian development and pathogenesisremain largely elusive. Here, we demonstrated that SENP2 plays a critical role in the control of hepatocellularcarcinoma cell growth. SENP2 was found to be down-regulated in hepatocellular carcinoma (HCC) tissues andover-expression suppressed the growth and colony formation of HCC cells. In contrast, silencing of SENP2 bysiRNAs promoted cancer cell growth. We further found that stability of β-catenin was markedly decreasedwhen SENP2 was over-expressed. Interestingly, the decrease was dependent on the de-SUMOylation activity ofSENP2, because over-expression of a SENP2 catalytic mutant form had no obviously effects on β-catenin. Ourresults suggest that SENP2 might play a role in hepatocellular carcinoma cell growth control by modulating thestability of β-catenin.     

Assessment of tumor budding in colorectal carcinoma: Correlation with β-catenin nuclear expression

BackgroundTumor budding (TB) is showing increasing promise as a colorectal cancer (CRC) prognosticator that is independent of TNM staging. β-Catenin is a component of the Wingless/Wnt signaling pathway that is bound to membrane-associated E-cadherin and is essential for its correct position and function.MethodsThis study was designed to detect TB in 44 resected primary CRC cases and also to compare β-catenin expression in the tumor budding sites (TBS) and in the tumor center. Tumor budding was assessed in both H&;E and pankeratin immunostained sections. Agreement between TB scoring using pancytokeratin and H&;E was tested. Also, typing of the tumor margin and determination of degree of cytoplasmic pseudo-fragmentation was done. Tumor budding, cytoplasmic pseudofragments and β-catenin expression were related to known CRC prognosticators.ResultsTen tumors (22.7%) showed low grade (LG) budding and 34 tumors (77.3%) showed high grade (HG) budding. The 34 HG budding tumors were further subdivided into moderate and severe (n = 13, n = 21, respectively) budding cancers. Twenty nine tumors (65.9%) showed LG cytoplasmic pseudofragments and 15 tumors (34.1%) showed HG pseudofragments. Scoring of TB on H&;E and pankeratin stained sections revealed moderate agreement (Kappa = .558; p = <.000).A significant relation between TB and cytoplasmic pseudofragments was observed (p = .009). Both TB and cytoplasmic pseudofragments did not significantly associate with clinicopathologic parameters. Immunoreactivity of nuclear and cytoplasmic β-catenin was significantly higher at TBS compared to tumor center (p = .005, p = .000, respectively). In opposition, membranous β-catenin expression was significantly higher in the tumor center than in TBS (p = .001). Although, nuclear β-catenin accumulation at TBS was noted, yet, it did not relate significantly with both TB and cytoplasmic pseudofragments around TBS (p = .649; p = .675, respectively). Also, nuclear β-catenin immunoreactivity did not relate significantly with the various clinicopathological variables.ConclusionPankeratin immunostaining facilitates typing of CRC invasive margin, and determination of the degree of TB and cytoplasmic pseudo-fragmentation. β-Catenin expression differs significantly between tumor center and TBS in CRC. Cut-offs for TB assessment should be unified and further studies are recommended to allow a better understanding of this process before establishing TB as a prognostic factor beyond the TNM staging in CRC.     

MicroRNA-200a suppresses the Wnt/β-catenin signaling pathway by interacting with β-catenin

The Wnt/β-catenin signaling pathway is crucial for human organ development and is involved in tumor progression of many cancers. Accumulating evidence suggests that the expression of β-catenin is, in part, regulated by specific microRNAs (miRNAs). The purpose of this study was to determine the expression of a recently identified epithelial to mesenchymal transition (EMT)-associated tumor suppressor microRNA (miR)-200a, in cancer cells. We also aimed to identify specific miR-200a target genes and to investigate the antitumor effects of miR-200a on the Wnt/β-catenin signaling pathway. We employed TOP/FOP flash luciferase assays to identify the effect of miR-200a on the Wnt/β-catenin pathway and we confirmed our observations using fluorescence microscopy. To determine target genes of miR-200a, a 3' untranslated region (3' UTR) luciferase assay was performed. Cell viability, invasion and wound healing assays were carried out for functional analysis after miRNA transfection. We further investigated the role of miR-200a in EMT by Western blot analysis. We found fluctuation in the expression of miR-200a that was accompanied by changes in the expression of members of the Wnt/β-catenin signaling pathway. We also determined that miR-200a can directly interact with the 3' UTR of CTNNB1 (the gene that encodes β-catenin) to suppress Wnt/β-catenin signaling. MiR-200a could also influence the biological activities of SGC790 and U251 cells. Our results demonstrate that miR-200a is a new tumor suppressor that can regulate the activity of the Wnt/β-catenin signaling pathway via two mechanisms. MiR-200a is a candidate target for tumor treatment via its regulation of the Wnt/β-catenin signaling pathway.     

Genetic ablation of β-catenin inhibits the proliferative phenotype of mouse liver adenomas

Background:

Aberrant activation of Wnt/β-catenin has been implicated in various cancer-related processes, for example, proliferation or tumour cell survival. However, the exact mechanism by which β-catenin provides liver tumour cells with a selective advantage is still unclear. This study was aimed to analyse growth behaviour and survival of β-catenin-driven mouse liver tumours after β-catenin ablation.

Methods:

Transgenic mice with a controllable hepatocyte-specific knockout of Ctnnb1 (encoding β-catenin) were generated and liver tumours were induced by means of a N-nitrosodiethylamine/phenobarbital tumour initiation/promotion protocol, which leads to the outgrowth of hepatocellular tumours with activated β-catenin. Cre recombinase was activated and the effects of the knockout in the tumours were studied.

Results:

Activation of Cre recombinase led to the knockout of Ctnnb1 in a fraction of tumour cells, thus resulting in the formation of two different tumour cell subpopulations, with or without β-catenin. Comparative analysis of the two subpopulations revealed that cell proliferation was significantly decreased in Ctnnb1-deleted hepatoma cells, compared with the corresponding non-deleted cell population, whereas no increased rate of apoptosis after knockout of Ctnnb1 was observed.

Conclusions:

β-catenin-dependent signalling is an important regulator of hepatoma cell growth in mice, but not a crucial factor in the regulation of tumour survival.     

eIF4EBP3 was downregulated by methylation and acted as a tumor suppressor by targeting eIF4E/β-catenin in gastric cancer

Gastric Cancer - Epigenetic aberrations of tumor suppressor genes (TSGs), particularly DNA methylation, are frequently involved in the pathogenesis of gastric cancer (GC). Through a methylome...     

MUC16 mucin (CA125) regulates the formation of multicellular aggregates by altering β-catenin signaling

After shedding from the primary tumor site, ovarian cancer cells form three-dimensional multicellular aggregates that serve as vehicle for cancer cell dissemination in the peritoneal cavity. MUC16 mucin (CA125) is aberrantly expressed by most advanced serous ovarian cancers and can promote proliferation, migration and metastasis. MUC16 associates with E-cadherin and β-catenin, two proteins involved in regulation of cell adhesion and the formation of multicellular aggregates. However, the role of MUC16 in the formation of multicellular aggregates remains to be defined. Here, we show that MUC16 alters E-cadherin cellular localization and expression. Consistent with this, MUC16 knockdown inhibited the formation of multicellular aggregates and, conversely, forced expression of MUC16 C-terminal domain (CTD) enhanced the formation of multicellular aggregates. MUC16 knockdown induces β-catenin relocation from the cell membrane to the cytoplasm, decreases its expression by increasing degradation and decreases β-catenin target gene expression. MUC16 CTD inhibits GSK-3β-mediated phosphorylation and degradation of β-catenin, leading to increased β-catenin levels. Importantly, knockdown of β-catenin inhibited multicellular aggregation. These findings indicate that MUC16 promotes the formation of multicellular aggregates by inhibiting β-catenin degradation.     

Loss of the 14-3-3σ tumor suppressor is a critical event in ErbB2-mediated tumor progression

14-3-3σ is a putative tumor suppressor involved in cell-cycle progression and epithelial polarity. We demonstrate that loss of one or both copies of the conditional 14-3-3σ allele results in accelerated mammary and salivary tumorigenesis in mice expressing an activated erbB2 oncogene under the endogenous erbB2 promoter. Significantly, the majority of tumors bearing a single conditional 14-3-3σ allele lose expression of the remaining 14-3-3σ allele, which is associated with epigenetic methylation of the 14-3-3σ locus. In addition to accelerated tumor onset, in a mouse mammary tumor virus-driven ErbB2 tumor model, loss of 14-3-3σ results in enhanced metastatic phenotype that is correlated with loss of cellular junctions. Taken together, these results provide compelling evidence that 14-3-3σ is a potent tumor suppressor involved in ErbB2-driven breast cancer initiation and metastasis. SIGNIFICANCE: 14-3-3σ has been identified as a normal mammary epithelial cell marker frequently downregulated during neoplastic development. Consistent with its potential role as a tumor suppressor, we demonstrate that targeted disruption of 14-3-3σ in a number of epithelial tissues can profoundly impact both the initiation and metastatic phases of ErbB2-mediated tumor progression through modulation of a number of distinct signaling networks.