Characterization of a beta-catenin nuclear localization defect in MCF-7 breast cancer cells

3D-microenvironments initiate TCF4 expression rescuing nuclear β-catenin activity in MCF-7 breast cancer cells

Mechanical cues sensed by tumor cells in their microenvironment can influence important mechanisms including adhesion, invasion and proliferation. However, a common mechanosensitive protein and/or pathway can be regulated in different ways among diverse types of tumors. Of particular interest are human breast epithelial cancers, which markedly exhibit a heterogeneous pattern of nuclear β-catenin localization, a protein known to be involved in both mechanotransduction and tumorigenesis. β-catenin can be aberrantly accumulated in the nucleus wherein it binds to and activates lymphoid enhancer factor/T cell factor (LEF/TCF) transcription factors. At present, little is known about how mechanical cues are integrated into breast cancer cells harboring impaired mechanisms of β-catenin's nuclear uptake and/or retention. This prompted us to investigate the influence of mechanical cues on MCF-7 human breast cancer cells which are known to fail in relocating β-catenin into the nucleus due to very low baseline levels of LEF/TCFs. Exploiting three-dimensional (3D) microscaffolds realized by two-photon lithography, we show that surrounding MCF-7 cells have not only a nuclear pool of β-catenin, but also rescue from their defective expression of TCF4 and boost invasiveness. Together with heightened amounts of vimentin, a β-catenin/TCF-target gene regulator of proliferation and invasiveness, such 3D-elicited changes indicate an epithelial-to-mesenchymal phenotypic switch of MCF-7 cells. This is also consistent with an increased in situ MCF-7 cell proliferation that can be abrogated by blocking β-catenin/TCF-transcription activity. Collectively, these data suggest that 3D microenvironments are per se sufficient to prime a TCF4-dependent rescuing of β-catenin nuclear activity in MCF-7 cells. The employed methodology could, therefore, provide a mechanism-based rationale to dissect further aspects of mechanotranscription in breast cancerogenesis, somewhat independent of β-catenin's nuclear accumulation. More importantly, by considering the heterogeneity of β-catenin signaling pathway in breast cancer patients, these data may open alternative avenues for personalized disease management and prevention. STATEMENT OF SIGNIFICANCE: Mechanical cues play a critical role in cancer pathogenesis. Little is known about their influence in breast cancer cells harboring impaired mechanisms of β-catenin's nuclear uptake and/or retention, involved in both mechanotransduction and tumorigenesis. We engineered 3D scaffold, by two-photon lithography, to study the influence of mechanical cues on MCF-7 cells which are known to fail in relocating β-catenin into the nucleus. We found that 3D microenvironments are per se sufficient to prime a TCF4-dependent rescuing of β-catenin nuclear activity that boost cell proliferation and invasiveness. Thus, let us suggest that our system could provide a mechanism-based rationale to further dissect key aspects of mechanotranscription in breast cancerogenesis and progression, somewhat independent of β-catenin's nuclear accumulation.

Silencing of CARMA3 inhibits bladder cancer cell migration and invasion via deactivating β-catenin signaling pathway

Background

Bladder cancer (BC) is the ninth most common cancer and the fourteenth leading death worldwide. CARD-containing MAGUK 3 (CARMA3) protein is a novel scaffold protein known to activate NF-κB pathway and is overexpressed in BC tissues.

Purpose

The objective of this study was to identify how CARMA3 affects the metastasis of BC cells via the β-catenin signaling pathway.

Materials and methods

In the present study, 5637 and T24 BC cells with stable low expression of CARMA3 were established, and their migratory and invasive capabilities were further evaluated by wound-healing and transwell assay. The activity and expression of β-catenin were determined by Luciferase assay and immunofluoresence staining. The mRNA and protein expression levels of CARMA3, matrix metallopeptidase (MMP) 9 and MMP2 were detected by quantitative real-time PCR (qRT-PCR) and Western blot analysis. The nude mouse tumor xenograft model was established for in vivo study.

Results

By comparison to the control cells, CARMA3-silenced cells acquired a less aggressive phenotype: decreased migration and invasion. More importantly, we confirmed that CARM3 knockdown could inhibit β-catenin mRNA and protein expression and activity, and reduce the expression and/or activity of matrix metallopeptidase (MMP) 9, MMP2 and C-myc. Also, CARM3 silencing increased E-cadherin expression and attenuated the expression of β-catenin. Moreover, we demonstrated that β-catenin overexpression reversed the inhibiting effect of CARMA3 silencing on cell invasion and migration. Furthermore, our study illustrated that knockdown of CARMA3 suppressed BC cells xenograft tumor growth in nude mice.

Conclusion

We demonstrated that CARMA3 contributes to the malignant phenotype of BC cells at least by activating β-catenin signaling pathway, and it may serve as a therapeutic target for clinic treatment in BC.

Proteomic screen with the proto-oncogene beta-catenin identifies interaction with Golgi coatomer complex I

Beta-catenin is well-known as a key effector of Wnt signalling and aberrant expression is associated with several human cancers. Stabilisation of and atypical subcellular localisation of beta-catenin, regulated in part through specific protein-protein interactions has been linked to cancer development, however the mechanisms behind these pathologies is yet to be fully elucidated. Affinity purification and mass spectrometry were used to identify potential β-catenin interacting proteins in SW480 colon cancer cells. Recombinant β-catenin constructs were used to co-isolate interacting proteins from stable isotope labelled cells followed by detection using mass spectrometry. Several known and new putative interactors were observed. In particular, we identified interaction with a set of coatomer complex I subunits implicated in retrograde transport at the Golgi, and confirmed endogenous interaction of β-catenin with coatomer subunit COPB using immunoprecipitation assays and immunofluorescence microscopy. These observations suggest a hitherto unrecognised role for β-catenin in the secretory pathway and warrant further functional studies to unravel its activity at this cellular location.

Serine protease modulation of Dependence Receptors and EMT protein expression

Expression of the tumour suppressor Deleted in Colorectal Cancer (DCC) and the related protein neogenin is reduced by the mammalian serine protease chymotrypsin or the bacterial serine protease subtilisin, with increased cell migration. The present work examines whether these actions are associated with changes in the expression of cadherins, β-catenin and vimentin, established markers of the Epithelial-Mesenchymal Transition (EMT) which has been linked with cell migration and tumour metastasis. The results confirm the depletion of DCC and neogenin and show that chymotrypsin and subtilisin also reduce expression of β-catenin in acutely prepared tissue sections but not in human mammary adenocarcinoma MCF-7 or MDA-MB-231 cells cultured in normal media, or primary normal human breast cells. A loss of β-catenin was also seen in low serum media but transfecting cells with a dcc-containing plasmid induced resistance. E-cadherin was not consistently affected but vimentin was induced by low serum-containing media and was increased by serine proteases in MCF-7 and MDA-MB-231 cells in parallel with increased wound closure. Vimentin might contribute to the promotion of cell migration. The results suggest that changes in EMT proteins depend on the cells or tissues concerned and do not parallel the expression of DCC and neogenin. The increased cell migration induced by serine proteases is not consistently associated with the expression of the EMT proteins implying either that the increased migration may be independent of EMT or supporting the view that EMT is not itself consistently related to migration. (241).

Nuclear β-catenin localization and mutation of the CTNNB1 gene: a context-dependent association

Although the majority of low-grade, early-stage endometrial cancer patients have good survival with surgery alone, patients who recur tend to do poorly. Identification of patients at high risk of recurrence who would benefit from adjuvant treatment or more extensive surgical staging would help optimize individualized care of endometrial cancer patients. CTNNB1 (encodes β-catenin) mutations identify a subset of low-grade, early-stage endometrial cancer patients at high risk of recurrence. Mutation of CTNNB1 exon 3 is classically associated with translocation of the β-catenin protein from the membrane to the nucleus and activation of Wnt/β-catenin signaling. Given the clinical utility of identifying endometrial carcinomas with CTNNB1 mutation, the purpose of this study was to determine if immunohistochemistry could act as a surrogate for CTNNB1 gene sequencing. Next-generation sequencing was performed on 345 endometrial carcinomas. Immunohistochemical localization of β-catenin was determined for 53/63 CTNNB1 exon 3 mutant tumors for which tissue was available and a subset of wild-type tumors. Nuclear localization of β-catenin had 100% specificity in distinguishing CTNNB1 mutant from wild type, but sensitivity was lower (84.9%). Nearly half of CTNNB1 mutant cases had only 5-10% of tumor cells with β-catenin nuclear localization. The concordance between pathologists blinded to mutation status in assessing nuclear localization was 100%. The extent of β-catenin nuclear localization was not associated with specific CTNNB1 gene mutation, tumor grade, presence of non-endometrioid component, or specific concurrent gene mutations in the tumor. For comparison, nuclear localization of β-catenin was more diffuse in desmoid fibromatosis, a tumor also associated with CTNNB1 mutation. Thus, nuclear localization of β-catenin assessed by immunohistochemistry does not detect all endometrial cancers with CTNNB1 gene mutation. The extent of nuclear localization may be tumor type dependent. For endometrial cancer, immunohistochemistry could be an initial screen, with CTNNB1 sequencing employed when nuclear localization of β-catenin is absent.

A Proteomics Analysis Reveals 9 Up-Regulated Proteins Associated with Altered Cell Signaling in Colon Cancer Patients

Colorectal cancer is the second most common cancer in women and third most common cancer in men. Cell signaling alterations in colon cancer, especially in aggressive metastatic tumors, require further investigations. The present study aims to compare the expression pattern of proteins associated with cell signaling in paired tumor and non-tumor samples of patients with colon cancer, as well as to define the cluster of proteins to differentiate patients with non-metastatic (Dukes' grade B) and metastatic (Dukes' grade C&D) colon cancer. Frozen tumor and non-tumor samples were collected after tumor resection from 19 patients with colon cancer. The Panorama™ Antibody Microarray-Cell Signaling kits were used for the analyses. The expression ratios of paired tumor/non-tumor samples were calculated for the each protein. We employed R packages 'samr', 'gplots', 'supclust' (pelora, wilma algorithms), 'glmnet' for the differential expression analysis, supervised clustering and penalized logistic regression. Significance analysis of microarrays revealed 9 significantly up-regulated proteins, including protein kinase C gamma, c-Myc, MDM2, pan cytokeratin, and 1 significantly down-regulated protein (GAP1) in tumoral mucosa. Pan-cytokeratin and APP were up-regulated in tumor versus non-tumor tissue, and were selected in the predictive cluster to discriminate colon cancer type. Higher levels of S-100b and phospho-Tau-pSer199/202 were confirmed as the predictors of non-metastatic colon cancer by all employed regression/clustering methods. Deregulated proteins in colon cancer are involved in oncogenic signal transduction, cell cycle control, and regulation of cytoskeleton/transport. Further studies are needed to validate potential protein markers of colon cancer development and metastatic progression.

High expression of SALL4 and fascin, and loss of E-cadherin expression in undifferentiated/dedifferentiated carcinomas of the endometrium: An immunohistochemical and clinicopathologic study

Undifferentiated/dedifferentiated endometrial carcinomas (UCE/DCEs) of the endometrium are rare tumors with poor prognosis. There are few clinicopathologic studies with detailed immunohistochemical analysis regarding UCE/DCEs.We evaluated the diagnostic value of a selected tumor stem-cell marker and epithelial-mesenchymal transition (EMT) markers, in addition to previously studied markers in identifying UCE/DCEs from other types of high-grade endometrial carcinomas.Eleven cases of UCE/DCEs with complete clinical follow-up that were diagnosed between 2006 and 2015 were included in the study. For immunohistochemical comparison, 11 clinically matched cases for each type of other high-grade endometrial carcinomas (high-grade endometrioid (F3-EC), serous [SC], and clear cell carcinoma [CCC]) were used as a control group. An immunohistochemical analysis including fascin, SALL4, E-cadherin, and β-catenin, in addition to epithelial and neuroendocrine markers was performed in each case.The majority of UCE/DCEs displayed diffuse expression of fascin (81.9%) and loss of E-cadherin expression (54.5%). SALL4 expression was detected in 36.3% of the UCE/DCE cases. SALL4 expression was significantly more frequent in UCE/DCEs than all other high-grade carcinomas (P < 0.001). Loss of E-cadherin and fascin expression was significantly more frequent in UCE/DCEs than high-grade endometrioid and clear cell adenocarcinomas (P = 0.012, 0.014 and P = 0.01, 0.003, respectively).We suggest that loss of E-cadherin expression together with fascin and SALL4 immunopositivity in addition to morphologic features have an impact in differential diagnosis of UCE/DCEs from other high-grade endometrial carcinomas.