Role Of Beta-catenin Research Articles

Role of Beta Catenin, GAB1, YAP1 and P53 Antibodies in the Molecular Classification of Medulloblastoma: Analysis of a Series of 68 Cases

Role of Beta Catenin, GAB1, YAP1 and P53 Antibodies in the Molecular Classification of Medulloblastoma: Analysis of a Series of 68 Cases

A Comparative Analysis of Immunohistochemical Profile of Primary and Metastatic Endometrial Endometrioid Carcinoma

Abstract Introduction/Objective Beta catenin plays an important role in cancer tumorigenesis and have been found to be associated with metastasis in a variety of tumors. Analyzing TCGA data, we found that 30% of endometrial endometrioid carcinoma cases have beta-catenin mutations. We hypothesize that beta-catenin mutation may be associated with metastasis of endometrial endometrioid carcinoma. ER and PR expression was also compared to determine any changes after metastasis. Methods Retrospective institutional review of all endometrial endometrioid carcinoma (192 cases) between 2011 to 2018 was performed, including 149 cases of FIGO grade I, 38 cases of FIGO grade II and 5 cases of FIGO grade III. 19 cases with paired primary and metastatic specimen were identified. Immunohistochemistry staining (IHC) was carried out for ER, PR and beta-catenin. Results Median patient age was 56 years. The most common metastatic site was vagina, accounting for 68% of metastasis (14/19), followed by bladder (3/19), lung (2/19) and rectum (1/19). The primary and metastatic carcinoma of all 19 cases exhibit very similar morphology. All of those cases were positive and concordant for ER and PR in primary and metastatic endometrioid carcinoma. On the other hand, nuclear beta-catenin staining caused by mutation was positive in 5 metastatic carcinoma but not in primary carcinoma. Conclusion IHC expression of ER and PR remains unchanged between primary and metastatic carcinoma, demonstrating the reliability of ER and PR to confirm the origin of metastatic carcinoma. 26% of the metastatic carcinoma (5/19) exhibit nuclear beta-catenin staining but not in primary carcinoma, suggesting the possible role of beta-catenin in metastasis of endometrial endometrioid carcinoma.

Role of beta-catenin on chondrocyte- and perichondrial-derived osteoblast differentiation

Role of beta-catenin on chondrocyte- and perichondrial-derived osteoblast differentiation

Association of different patterns of expression of beta-catenin and cyclin D1 with pathogenesis of breast carcinoma.

Beta-catenin and cyclin D1 have attracted considerable attention in recent studies as potential proto-oncogenes in many human cancers especially colonic cancer. Beta-catenin plays multiple roles within the cell such as canonical Wnt signaling where cyclin D1 has been identified as one of its target genes. The role of beta-catenin and cyclin D1 in breast cancer has been evaluated in many studies but not established yet. The expression of beta-catenin and cyclin D1 was evaluated in 82 cases of breast carcinoma (BCa) and 32 cases of ductal carcinoma in situ(DCIS) by immunohistochemistry (IHC). Their relationship with clinicopathological features was also investigated. Statistical analysis was done to establish an association. Abnormal expression of beta-catenin (ABE) was seen in 80.2% cases of invasive ductal carcinoma (IDC) and 47% cases of DCIS, while the cyclin D1 positive expression rate was 60.9% and 50%, respectively. In the cases showing ABE, cyclin D1 positivity was 88.1%. ABE showed significant association with high-grade BCa. The most common pattern of ABE was loss of membrane with nuclear positivity which is associated with worst prognosis. In addition, ABE in cases of BCa and DCIS showed concordant patterns. Therefore, an association exists between ABE and cyclin D1 in BCa and its precursor lesions implying that Wnt/beta-catenin oncogenic pathway may have a definite role in breast carcinogenesis and can be used for targeted therapy. Also, different patterns of beta-catenin expression may have prognostic and predictive value.

Abstract 1926: The effect of Beta-Catenin upon the tumor molecular biology and growth in HNSCC: role of cancer stem cells

Abstract Overview: Head and neck squamous cell carcinomas (HNSCC) are the sixth most prevalent type of malignancy worldwide. Recent reports have demonstrated that nearly every tumor contain a small subpopulation of cells called cancer stem-like cells (CSCs), which are responsible for tumor maintenance, metastasis relapse and therapeutic resistance. Recent studies demonstrate that even established HNSCC cell lines contain a definite sub-population of CSC providing us with the opportunity to discerning their roles in progression, treatment, and relapse of the disease. Background: We have previously demonstrated that a definite subpopulation of CSCs exists in most HNSCC cell lines. Significant differences were seen between the HPV+ and HPV- subtypes, confirmed by analyses of stem-ness genes and EMT markers. In vivo tumor xenograft formation has established the heightened tumorigenicity of CSCs. We investigated the molecular and functional roles of Beta-catenin in HNSCC CSCs by shRNA knock down and then subjecting the knocked down (KD) cells to various molecular analysis and in-vivo tumor formations in nude mice. We have also identified SOX2 as a down-stream effector gene that could exert the tumor promoting effects of Beta-catenin. The promoter region of the Sox2 gene was found to contain several putative Beta-catenin binding sites. Methods & Results: After identifying CSCs by in-vitro Sphere Forming (SFA) capabilities and molecular gene signatures, we have knocked down both Beta-catenin and Sox2 in both HPV+ and HPV- HNSCC cell lines (UMSCC47 and UMSCC6). SFA with the Beta-catenin KD-cells depicts a 50% decrease in sphere formation ability. Molecular analyses show lower expression of stemness genes: Sox2 (~ 3 fold) and Oct4 (~ 2 fold); metastatic genes: N-cadherin (~ 2.5 fold), Vimentin (~ 3 fold), Twist (~ 4 fold), Snail (~ 2.5 fold), Slug (~ 2.5 fold) and Hif-1alpha (~ 1.5 fold). Two tissue microarrays (TMA) were stained for Oct4, Sox2, and CD44 gene expression by multiplex RNA in situ hybridization. Nearly all tumor cells expressed high levels of CD44. Cells high in both Oct4 and Sox2 were quantified within duplicate cores and correlated with local control (TMA-1) and radiation response (TMA-2). Conclusions: Initial molecular analyses depicted that upon loss of Beta-catenin, the crucial stem-ness genes are negatively affected and the loss of stem-ness is also reinforced by decreased sphere formations. Both the metastatic and hypoxic gene signatures are markedly altered. We expect similar outcomes with the in-vivo tumor formations in nude mice. Citation Format: Austin Maas, Anirban Chatterjee, Lisa Sudmeier, Kwang Nickel, Randall J. Kimple. The effect of Beta-Catenin upon the tumor molecular biology and growth in HNSCC: role of cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1926. doi:10.1158/1538-7445.AM2017-1926

Role of beta-catenin and endocannabinoids in the nucleus accumbens in extinction in rats exposed to shock and reminders

The response to a traumatic experience may be rapid recovery or development of psychopathology such as post-traumatic stress disorder (PTSD). Impaired extinction of fear memories is thought to contribute to the development of the persistent trauma memories and avoidance.The Wnt/β-catenin pathway and the endocannabinoid system appear to play significant roles in anxiety and depressive symptoms. Here we examined the involvement of β-catenin in the nucleus accumbens (NAc) in extinction in rats exposed to the shock and reminders model of PTSD.We found that increased β-catenin levels in the NAc were correlated with facilitated extinction kinetics in rats exposed to shock and reminders, suggesting that increased levels of NAc β-catenin are associated with a resilient response to the stressor. Furthermore, downregulating β-catenin expression in the NAc in shocked rats using sulindac (0.0178, 0.178mg/side) impaired extinction whereas upregulating the Wnt/β-catenin pathway using LiCl (2µg/side) facilitated extinction. Exposure to shock and reminders resulted in attenuated levels of the endocannabinoid N-arachidonylethanolamine (AEA) in the NAc; the cannabinoid CB1/2 receptor agonist WIN55,212-2 (5µg/side) microinjected into the NAc facilitated extinction in shocked rats. Importantly, the facilitating effect of WIN55,212-2 on extinction was blocked by co-administration of sulindac in doses that downregulated β-catenin levels.Taken together, the results suggest that β-catenin in the NAc may serve as a protective buffer against the effects of severe stress, and that inhibiting this system in the NAc may prevent the therapeutic effects of cannabinoids against stress-related disorders.

Micro RNA-214 contributes to proteasome independent downregulation of beta catenin in Huntington's disease knock-in striatal cell model STHdhQ111/Q111

Role of beta catenin in Huntington's disease (HD) is not clear. Previous studies on HD reported varied levels of beta catenin. In the present study we showed that beta catenin is post transcriptionally down-regulated in mutant huntingtin knock-in cell model STHdhQ111/Q111. This in turn leads to decreased level of wnt/beta catenin responsive genes. We observed that Gsk3beta or Gsk3beta (phospho Ser 9) is unaltered in HD and this down-regulation of beta catenin is independent of proteasomal degradation. Finally, we showed that the overexpression of miR-214 leads to the down-regulation of beta catenin at protein level only and reduces its transcriptional activity. We concluded that, miR-214 contributes to the processes that result in proteasome independent post transcriptional down-regulation of beta catenin in STHdhQ111/Q111, probably through inhibition of protein synthesis from beta catenin mRNA.

Abstract 1314: Aberrant expression of beta-catenin and cyclin D1 in endometrial cancer

Abstract Introduction: Wnt/beta-catenin/cyclin D1 pathway has been suggested to be involved in cell proliferation in endometrioid endometrial carcinomas (EEC), in addition to the activation of the PI3K pathway via PIK3CA and/or PTEN mutations. We previously reported that the mutations of cyclin D1 (CCND1 gene) promotes cell proliferation in EEC. However, the role of beta-catenin and its relationship with cyclin D1 is not yet well known. In this study, we focused on alterations of beta-catenin and cyclin D1 and their clinical impact in EEC. Methods: This study was conducted under approval of ethics committee of the institute and informed consent from each patient. Expressions of cyclin D1 and beta-catenin were examined by tissue microarray in formalin fixed 120 samples of EEC. The expression levels were evaluated by two pathologists, and the staining was classified as overexpressed when >50% of tumor cells showed strong staining in cytoplasm (for beta-catenin) and nucleus (for cyclin D1). Genomic DNA was isolated in 91 primary surgical specimens. Mutations of beta-catenin (exon 3 of CTNNB1 gene) and Cyclin D1 (exon 5 of CCND1 gene) were examined by PCR-direct sequencing. We constructed expression plasmid of various types of mutant beta-catenin and performed colony formation assay using these plasmids. Result: In 120 samples, beta catenin and cyclin D1 were overexpressed in 5 (4%) and 7 (6%) cases, respectively. Median follow-up period of these patients is 85 months. Interestingly, over-expression of these two proteins was not overlapped each other. In these 12 samples, 7 of 12 cases (58%) were stage III or IV. However, recurrence was only observed in one patient (5-year progression free survival rate is 92%). Mutations of CCND1 and CTNNB1 were detected in 2 (2%) and 9 (10%) cases, respectively. We confirmed that all these mutations are somatic. Mutations of CCND1 and CTNNB1 were also mutually exclusive. Although the two cases with CCND1 mutations died of disease, none of the nine cases with CTNNB1 mutations got recurrent (p=0.018 by Fisher's exact test). In colony formation assay, mutant beta-catenin at codon 32 and codon 37 did not increase the colony number, compared with wild-type beta-catenin (control), although mutants at codon 34 significantly augmented the colony formation. Conclusion: Aberrant expression of both beta-catenin and cyclin D1 are present in EEC, through mutations and/or overexpression, and alterations of beta-catenin might be associated with favorable prognosis. Our data suggest that function of mutant beta-catenin might be distinct among each mutation type. Further study is warranted to clarify the role of wnt/beta-catenin/cyclin D1 pathway in EEC. Citation Format: Yuji Ikeda, Katsutoshi Oda, Takahiro Koso, Daichi Maeda, Osamu Wada Hiraike, Tomoko Kashiyama, Aki Miyasaka, Kei Kawana, Tetsu Yano, Yoshihiro Kikuchi, Masashi Fukayama, Yutaka Osuga, Tomoyuki Fujii. Aberrant expression of beta-catenin and cyclin D1 in endometrial cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1314. doi:10.1158/1538-7445.AM2014-1314

Sonic hedgehog maintains survival and growth of chronic myeloid leukemia progenitor cells through β-catenin signaling

Sonic hedgehog (Shh) signaling plays an important role in many human cancers and cancer stem cells. Here we investigate the activity and functional role of Shh signaling in chronic myeloid leukemia (CML) and leukemia progenitor cells. Differential activation of Shh signaling was found in about 50% CML chronic phase samples, about 70% of CML accelerated phase samples, and >80% CML blast crisis phase samples. Deregulated activation of Shh signaling was observed in CD34(+) and c-kit(+) leukemia progenitor cells. Stimulation of Shh signaling with exogenous Shh peptide induced expansion of CD34(+) and c-kit(+) progenitor cells (p < 0.05), inversely, blocking the pathway with signal inhibitor induced cell apoptosis (p < 0.05). Low level of Shh protein was observed in CML bone marrow stromal cells, and CD34(+) progenitor cells are less sensitive to exogenous Shh peptide and more sensitive to cyclopamine than CD34(-) cells (p < 0.05), implying cell-autonomous activation of Shh signaling play a predominant role in progenitor cells. Coactivation of Shh and β-catenin signaling was found in CD34(+) and c-kit(+) progenitor cells. Administration of Shh-neutralizing antibody or Wnt3a-neutralizing antibody in c-kit(+) progenitor cells induced cell apoptosis; however, Wnt3a peptide could salvage cell apoptosis, while Shh peptide failed to revert anti-Wnt3a-induced cell apoptosis. C-MYC, GLI1, BCL-2, and P21 were also found to be downstream targets of Shh signaling, mediating apoptosis or G(2)/M cell cycle arrest of progenitor cells. Our results demonstrate that autoactivated Shh signaling provides survival and proliferative cues in CML progenitor cells through downstream β-catenin signaling, suggesting a novel therapeutic approach in CML.

Cushing's Syndrome in an Infant Secondary to Malignant Adrenocortical Tumors with Somatic Mutation of Beta-Catenin

A role of beta-catenin (CTNNB1) in the molecular pathogenesis of adrenocortical carcinoma (ACC) has been suspected in adult ACC and pediatric pigmented nodular adrenocortical disease, but it has never been reported in pediatric ACC. We present the case of a 4-month-old Thai infant who had Cushing's syndrome secondary to bilateral adrenal tumors with hepatic metastasis. The child was successfully treated with a bilateral adrenalectomy and wedge resection of the liver nodule. Histopathology revealed bilateral adrenocortical tumors with different histologic grades; the right tumor had a higher score, according to modified Weiss criteria. On molecular study, a deletion mutation of beta-catenin involving codons 44 to 45 was detected in the right adrenal tumor. The same mutation was found in peripheral blood before treatment; this mutation disappeared after tumor removal. The left tumor harbored wild-type beta-catenin. Immunohistochemistry showed nuclear accumulation of beta-catenin on the right adrenal tumor and the metastatic nodule. In summary, we present evidence that supports the role of the Wnt-signaling pathway in the carcinogenesis of pediatric adrenocortical carcinoma.

Early changes of beta-Catenins and Menins in spinal cord dorsal horn after peripheral nerve injury.

Injury to the peripheral nervous system can lead to spontaneous pain, hyperalgesia and allodynia. Previous studies have shown sprouting of Abeta-fibres into lamina II of the spinal cord dorsal horn after nerve injury and the formation of new synapses by these sprouts. beta-Catenin and menin as synaptogenic factors are critically involved in synapse formation. However, the roles of beta-catenin and menin in neuropathic pain are still unclear. Using Western blot analysis we investigated the changes of beta-catenin and menin in the spinal dorsal horn after unilateral spared nerve injury (SNI). We demonstrated an increase in both beta-catenin and menin protein levels in the ipsilateral spinal dorsal horn at days 1 and 3 following spared nerve injury (P < 0.05). These increases were associated with changes in paw withdrawal threshold to mechanical stimuli and weight bearing deficit suggestive of pain behavior and spontaneous ongoing pain respectively. However, the injury-associated increases in beta-catenins and menins levels returned to control levels at day 14. In conclusion, these results indicate that peripheral nerve injury induces upregulation of beta-catenins and menins in the dorsal horn of the spinal cord, which may contribute to the development of chronic neuropathic pain. Antagonists of these molecules may serve as new therapeutic agents.

β‐Catenin—A supporting role in the skeleton

In the last 5 years a role for beta-catenin in the skeleton has been cemented. Beginning with mutations in the Lrp5 receptor that control beta-catenin canonical downstream signals, and progressing to transgenic models with bone-specific alteration of beta-catenin, research has shown that beta-catenin is required for normal bone development. A cell critical to bone in which beta-catenin activity determines function is the marrow-derived mesenchymal stem cell (MSC), where sustained beta-catenin prevents its distribution into adipogenic lineage. beta-Catenin actions are less well understood in mature osteoblasts: while beta-catenin contributes to control of osteoclastic bone resorption via alteration of the osteoprotegerin/RANKL ratio, a specific regulatory role during osteoblast bone synthesis has not yet been determined. The proven ability of mechanical factors to prevent beta-catenin degradation and induce nuclear translocation through Lrp-independent mechanisms suggests processes by which exercise might modulate bone mass via control of lineage allocation, in particular, by preventing precursor distribution into the adipocyte pool. Effects resulting from mechanical activation of beta-catenin in mature osteoblasts and osteocytes likely modulate bone resorption, but whether beta-catenin is involved in osteoblast synthetic function remains to be proven for both mechanical and soluble mediators. As beta-catenin appears to support the downstream effects of multiple osteogenic factors, studies clarifying when and where beta-catenin effects occur will be relevant for translational approaches aimed at preventing bone loss and terminal adipogenic conversion.

β-Catenin is involved in alterations in mitochondrial activity in non-transformed intestinal epithelial and colon cancer cells

Background:Alteration in respiratory activity and mitochondrial DNA (mtDNA) transcription seems to be an important feature of cancer cells. Leukotriene D4 (LTD4) is a proinflammatory mediator implicated in the pathology of chronic inflammation and cancer. We have shown earlier that LTD4 causes translocation of β-catenin both to the mitochondria, in which it associates with the survival protein Bcl-2 identifying a novel role for β-catenin in cell survival, and to the nucleus in which it activates the TCF/LEF transcription machinery.Methods:Here we have used non-transformed intestinal epithelial Int 407 cells and Caco-2 colon cancer cells, transfected or not with wild type and mutated (S33Y) β-catenin to analyse its effect on mitochondria activity. We have measured the ATP/ADP ratio, and transcription of the mtDNA genes ND2, ND6 and 16 s in these cells stimulated or not with LTD4.Results:We have shown for the first time that LTD4 triggers a cellular increase in NADPH dehydrogenase activity and ATP/ADP ratio. In addition, LTD4 significantly increased the transcription of mtDNA genes. Overexpression of wild-type β-catenin or a constitutively active β-catenin mutant mimicked the effect of LTD4 on ATP/ADP ratio and mtDNA transcription. These elevations in mitochondrial activity resulted in increased reactive oxygen species levels and subsequent activations of the p65 subunit of NF-κB.Conclusions:The present novel data show that LTD4, presumably through β-catenin accumulation in the mitochondria, affects mitochondrial activity, lending further credence to the idea that inflammatory signalling pathways are intrinsically linked with potential oncogenic signals.

Desmoid tumor: from surgical extirpation to molecular dissection

Desmoid tumors are associated with a variable and unpredictable clinical course. Surgery is the therapeutic mainstay, but there has been much discussion of late regarding its proper application. Little is known regarding the molecular determinates of desmoid tumor behavior. Some recent work has focused on the role of beta-catenin in desmoid tumor biology. Given the variable clinical course of desmoid tumors, the interpretation of factors classically associated with recurrence such as microscopic status of margins appears more nuanced that previously thought. The application of multidisciplinary assessment with multimodality treatment, including surgery, radiation and systemic therapies may underlie these changes and now form the basis of care for this tumor. The precise CTNNB1 mutation present appears to be strongly predictive of recurrence after initial resection in one large, retrospective, multivariate analysis. Establishing the population benefiting most from various treatment modalities and combinations is critical for progress in this disease. Assessment and treatment of individual patients in a multidisciplinary setting is critical to achieve the most favorable outcome. Additional study of the molecular determinates of desmoid behavior is needed to guide therapeutic selection.

Differential role of β‐catenin in VEGF and histamine‐induced MMP‐2 production in microvascular endothelial cells

Increases in endothelial cell permeability and production of matrix-degrading enzymes are two early steps in the angiogenic process. Factors such as vascular endothelial growth factor (VEGF) and histamine induce the angiogenic process through alterations in both permeability and proteolysis. We hypothesized that beta-catenin acts as a positive regulator of MMP-2 and MT1-MMP transcription following VEGF or histamine stimulation. Rat microvascular endothelial cells were exposed to VEGF or histamine overnight and MMP-2 protein production was assessed by gelatin zymography. Latent MMP-2 protein levels were increased following VEGF and histamine treatment as were MMP-2 mRNA transcript levels. Endothelial cells exposed to VEGF and histamine had an increased level of nuclear beta-catenin, which was sensitive to inhibition of the PI3-kinase signaling pathway. Promoter assays indicated increased transcriptional activity of both MMP-2 and MT1-MMP in endothelial cells co-transfected with luciferase reporter constructs and beta-catenin. Inhibition of beta-catenin signaling with inhibitor of catenin and T cell factor (ICAT) revealed that the VEGF-induced increase in MMP-2 mRNA is beta-catenin dependent. Interestingly, while MMP-2 mRNA levels increased in response to histamine H1 or H2 receptor activation, significantly larger increases were observed in cells co-treated with ICAT and histamine or the histamine receptor agonists, HTMT and dimaprit. While both VEGF and histamine increase nuclear beta-catenin and MMP-2 production, the role of beta-catenin in MMP-2 regulation differs between the two stimuli.

Targeting PKC: a novel role for beta-catenin in ER stress and apoptotic signaling

AbstractTargeting protein kinase C (PKC) isoforms by the small molecule inhibitor enzastaurin has shown promising preclinical activity in a wide range of tumor cells. We further delineated its mechanism of action in multiple myeloma (MM) cells and found a novel role of β-catenin in regulating growth and survival of tumor cells. Specifically, inhibition of PKC leads to rapid accumulation of β-catenin by preventing the phosphorylation required for its proteasomal degradation. Microarray analysis and small-interfering RNA (siRNA)–mediated gene silencing in MM cells revealed that accumulated β-catenin activates early endoplasmic reticulum stress signaling via eIF2α, C/EBP-homologous protein (CHOP), and p21, leading to immediate growth inhibition. Furthermore, accumulated β-catenin contributes to enzastaurin-induced cell death. Sequential knockdown of β-catenin, c-Jun, and p73, as well as overexpression of β-catenin or p73 confirmed that accumulated β-catenin triggers c-Jun–dependent induction of p73, thereby conferring MM cell apoptosis. Our data reveal a novel role of β-catenin in endoplasmic reticulum (ER) stress-mediated growth inhibition and a new proapoptotic mechanism triggered by β-catenin on inhibition of PKC isoforms. Moreover, we identify p73 as a potential novel therapeutic target in MM. Based on these and previous data, enzastaurin is currently under clinical investigation in a variety of hematologic malignancies, including MM.

RALT Specifically Halts Maladaptive Cardiac Hypertrophy

The adult heart enlarges and increases in weight in response to ischemic stress and hypertension, a process termed cardiac hypertrophy. However, the heart also increases in size after regular physiological exercise. Cardiac hypertrophy is recognized as an important process in the development of heart failure. Initial results pointed to a clear signaling pattern of physiological hypertrophy after training versus pathological hypertrophy after damage. Although the signaling mechanisms involved have been studied for more than a decade, there is no clear distinction at the molecular level of physiological and pathological hypertrophy.1 Rather, the balance between signaling pathways preventing deterioration and pathways activated in association with preserving left ventricular function is regarded as critical. Accordingly, the terms adaptive and maladaptive were introduced to reflect these processes, respectively.2 A potential treatment avenue could be to selectively identify pathways involved in maladaptive hypertrophy that could be blocked. Alternatively, enhancing signaling pathways specifically involved in adaptive hypertrophy might allow us to conserve left ventricular function. Cai et al have identified a new target in cardiac hypertrophy: the receptor-associated late transducer (RALT).3 RALT appears to be a specific antagonist of maladaptive hypertrophy (Figure). Mechanistically, RALT functions as a negative regulator of epidermal growth factor receptor-mediated signaling not only in the heart but in other organs as well. The investigators used angiotensin II and isoproterenol as stimuli for stress-induced, maladaptive left ventricular remodeling in transgenic mice overexpressing RALT under the control of the α-myosin heavy …

Activation of β-Catenin Signaling in Articular Chondrocytes Leads to Osteoarthritis-Like Phenotype in Adult β-Catenin Conditional Activation Mice

Osteoarthritis (OA) is a degenerative joint disease, and the mechanism of its pathogenesis is poorly understood. Recent human genetic association studies showed that mutations in the Frzb gene predispose patients to OA, suggesting that the Wnt/beta-catenin signaling may be the key pathway to the development of OA. However, direct genetic evidence for beta-catenin in this disease has not been reported. Because tissue-specific activation of the beta-catenin gene (targeted by Col2a1-Cre) is embryonic lethal, we specifically activated the beta-catenin gene in articular chondrocytes in adult mice by generating beta-catenin conditional activation (cAct) mice through breeding of beta-catenin(fx(Ex3)/fx(Ex3)) mice with Col2a1-CreER(T2) transgenic mice. Deletion of exon 3 of the beta-catenin gene results in the production of a stabilized fusion beta-catenin protein that is resistant to phosphorylation by GSK-3beta. In this study, tamoxifen was administered to the 3- and 6-mo-old Col2a1-CreER(T2);beta-catenin(fx(Ex3)/wt) mice, and tissues were harvested for histologic analysis 2 mo after tamoxifen induction. Overexpression of beta-catenin protein was detected by immunostaining in articular cartilage tissues of beta-catenin cAct mice. In 5-mo-old beta-catenin cAct mice, reduction of Safranin O and Alcian blue staining in articular cartilage tissue and reduced articular cartilage area were observed. In 8-mo-old beta-catenin cAct mice, cell cloning, surface fibrillation, vertical clefting, and chondrophyte/osteophyte formation were observed. Complete loss of articular cartilage layers and the formation of new woven bone in the subchondral bone area were also found in beta-catenin cAct mice. Expression of chondrocyte marker genes, such as aggrecan, Mmp-9, Mmp-13, Alp, Oc, and colX, was significantly increased (3- to 6-fold) in articular chondrocytes derived from beta-catenin cAct mice. Bmp2 but not Bmp4 expression was also significantly upregulated (6-fold increase) in these cells. In addition, we also observed overexpression of beta-catenin protein in the knee joint samples from patients with OA. These findings indicate that activation of beta-catenin signaling in articular chondrocytes in adult mice leads to the premature chondrocyte differentiation and the development of an OA-like phenotype. This study provides direct and definitive evidence about the role of beta-catenin in the development of OA.

Targeting PKC: A Novel Role for Beta-catenin in ER Stress and Apoptotic Signaling

Targeting protein kinase C (PKC) isoforms by the small molecule inhibitor enzastaurin has shown promising pre-clinical activity in a wide range of tumor cells. In this study, we further delineated its mechanism of action in multiple myeloma (MM) cells and found a novel role of b-catenin in regulating growth and survival of tumor cells. Inhibition of PKC leads to rapid accumulation of b-catenin by preventing the phosphorylation required for its proteasomal degradation. Specifically, b-catenin was dephosphorylated at Ser33,37,41 and accumulated in a dose- and time-dependent manner in all cell lines tested (including primary MM cells and 10 MM cell lines, 3 colon cancer, HeLa, as well as HEK 293 cells). Microarray analysis and siRNA-mediated gene silencing in MM cells revealed that accumulated b-catenin activates early ER stress signaling via eIF2a, CHOP and p21, leading to immediate inhibition of proliferation. Conversely, knock-down of components of the ER stress response pathway by siRNA (i.e., CHOP) abrogated the inhibitory effect of enzastaurin on MM cell proliferation. Importantly, accumulated b-catenin also contributes to enzastaurin-induced cell death, since inhibition of b-catenin by siRNA partially rescued HeLa, HEK 293, and MM cells from cell death induced by enzastaurin. Analysis of downstream target molecules revealed a b-catenin -dependent up-regulation of c-Jun, but not of c-Myc or Cyclin D1. c-Jun has been reported to stabilize p73, a pro-apoptotic p53-family member; b-catenin induction by enzastaurin led to p73 (but not p53) activation, which was also abrogated by b-catenin -specific siRNA. In turn, specific knockdown of p73 by siRNA rescued cells from enzastaurin-induced apoptosis. Finally, ectopic overexpression of b-catenin in HeLa and MM cells induced c-Jun expression and p73 activation, followed by apoptotic cell death. In summary, our data reveal a novel role of b-catenin in ER stress-mediated growth inhibition and a new pro-apoptotic mechanism triggered by b-catenin upon inhibition of PKC isoforms, and further demonstrate that p73 represents a novel therapeutic target in MM. Based on these and previous data, enzastaurin is currently under clinical investigation in a variety of hematologic malignancies including MM.

The GSK-3/β-catenin-signalling axis in smooth muscle and its relationship with remodelling

β-Catenin is a plasma membrane-associated protein that plays a dual role in cellular signalling by stabilizing cadherin mediated cell–cell contact and by regulating TCF-/LEF-mediated gene transcription. Traditionally, the role of β-catenin in health and disease has mainly been studied in the context of development and uncontrolled cell growth in diseases such as cancer. Recent findings indicate, however, that β-catenin also plays a significant role in fibro-proliferative diseases of several organ systems and that β-catenin regulates mitogenic responses of smooth muscle cells. As several diseases of the internal organs are characterized by structural and phenotypic abnormalities of smooth muscle, including increased fibro-proliferative responses, these findings implicate that β-catenin could play a broad pathophysiological role. This article will review this potential novel role for β-catenin and associated intracellular signalling in smooth muscle and discuss the hypothesis that it plays a central role in smooth muscle remodelling.