Wnt signaling pathway is activated in right colon serrated polyps correlating to specific molecular form of β-catenin

MCC Gene Silencing Is a CpG Island Methylator Phenotype-Associated Factor That Predisposes Colon Cancer Cells to Irinotecan and Olaparib

Simple Summary

DNA hypermethylation of specific regulatory regions causes gene silencing that is an important cancer-promoting mechanism. A subset of colorectal cancers display concordant hypermethylation and silencing of multiple genes, and this appears to change the way in which tumors respond to some cancer therapies. The aim of this study was to evaluate how the presence of the MCC gene silencing relates to the highly methylated subset of colorectal cancers and how it may affect therapy responsiveness. We found that strong MCC silencing is found throughout the hypermethylated subset, but MCC expression is also lost or reduced in some other tumors which show hypomethylated regions of the gene. In cell culture experiments, the deletion of MCC increased the responsiveness of cancer cells to the chemotherapy drug irinotecan (SN38), and this was further augmented by a targeted cancer drug, the PARP-inhibitor Olaparib.

Abstract

Chemotherapy is a mainstay of colorectal cancer treatment, and often involves a combination drug regime. CpG island methylator phenotype (CIMP)-positive tumors are potentially more responsive to the topoisomerase-inhibitor irinotecan. The mechanistic basis of the increased sensitivity of CIMP cancers to irinotecan is poorly understood. Mutated in Colorectal Cancer (MCC) is emerging as a multifunctional tumor suppressor gene in colorectal and liver cancers, and has been implicated in drug responsiveness. Here, we found that CIMP tumors undergo MCC loss almost exclusively via promoter hypermethylation rather than copy number variation or mutations. A subset of cancers display hypomethylation which is also associated with low MCC expression, particularly in rectal cancer, where CIMP is rare. MCC knockdown or deletion was found to sensitize cells to SN38 (the active metabolite of irinotecan) or the PARP-inhibitor Olaparib. A synergistic effect on cell death was evident when these drugs were used concurrently. The improved SN38/irinotecan efficacy was accompanied by the down-regulation of DNA repair genes. Thus, differential methylation of MCC is potentially a valuable biomarker to identify colorectal cancers suitable for irinotecan therapy, possibly in combination with PARP inhibitors.

Molecular Mechanisms of the Action of Myricetin in Cancer

Natural compounds, such as paclitaxel and camptothecin, have great effects on the treatment of tumors. Such natural chemicals often achieve anti-tumor effects through a variety of mechanisms. Therefore, it is of great significance to conduct further studies on the anticancer mechanism of natural anticancer agents to lay a solid foundation for the development of new drugs. Myricetin, originally isolated from Myrica nagi, is a natural pigment of flavonoids that can inhibit the growth of cancer cells (such as liver cancer, rectal cancer, skin cancer and lung cancer, etc.). It can regulate many intracellular activities (such as anti-inflammatory and blood lipids regulation) and can even be bacteriostatic. The purpose of this paper is to outline the molecular pathways of the anticancer effects of myricetin, including the effect on cancer cell death, proliferation, angiogenesis, metastasis and cell signaling pathway.

Mouse Model of Mutated in Colorectal Cancer Gene Deletion Reveals Novel Pathways in Inflammation and Cancer

BACKGROUND & AIMS

The early events by which inflammation promotes cancer are still not fully defined. The MCC gene is silenced by promoter methylation in colitis-associated and sporadic colon tumors, but its functional significance in precancerous lesions or polyps is not known. Here, we aimed to determine the impact of Mcc deletion on the cellular pathways and carcinogenesis associated with inflammation in the mouse proximal colon.

METHODS

We generated knockout mice with deletion of Mcc in the colonic/intestinal epithelial cells (Mcc^ΔIEC) or in the whole body (Mcc^Δ/Δ). Drug-induced lesions were analyzed by transcriptome profiling (at 10 weeks) and histopathology (at 20 weeks). Cell-cycle phases and DNA damage proteins were analyzed by flow cytometry and Western blot of hydrogen peroxide-treated mouse embryo fibroblasts.

RESULTS

Transcriptome profiling of the lesions showed a strong response to colon barrier destruction, such as up-regulation of key inflammation and cancer-associated genes as well as 28 interferon γ-induced guanosine triphosphatase genes, including the homologs of Crohn's disease susceptibility gene IRGM. These features were shared by both Mcc-expressing and Mcc-deficient mice and many of the altered gene expression pathways were similar to the mesenchymal colorectal cancer subtype known as consensus molecular subtype 4 (CMS4). However, Mcc deletion was required for increased carcinogenesis in the lesions, with adenocarcinoma in 59% of Mcc^ΔIEC compared with 19% of Mcc-expressing mice (P = .002). This was not accompanied by hyperactivation of β-catenin, but Mcc deletion caused down-regulation of DNA repair genes and a disruption of DNA damage signaling.

CONCLUSIONS

Loss of Mcc may promote cancer through a failure to repair inflammation-induced DNA damage. We provide a comprehensive transcriptome data set of early colorectal lesions and evidence for the in vivo significance of MCC silencing in colorectal cancer.

Fusobacterium nucleatum promotes M2 polarization of macrophages in the microenvironment of colorectal tumours via a TLR4-dependent mechanism

Fusobacterium nucleatum (Fn) has been shown to promote colorectal cancer (CRC) development by inhibiting host anti-tumour immunity. However, the impact of Fn infection on macrophage polarization and subsequent intestinal tumour formation as well as the underlying molecular pathways has not been investigated. We investigated the impact of Fn infection on macrophage polarization in human CRCs and cultured macrophages as well as the effects on macrophage phenotype and intestinal tumour formation in ApcMin/+ mice. We also examined whether macrophage-polarized activation challenged by Fn infection via a TLR4-dependent mechanism involved the IL-6/STAT3/c-MYC signalling cascade. Our data showed that macrophages are a major tumour-infiltrating immune cell type in human CRCs with Fn infection (P < 0.001). Fn infection increased M2 polarization of macrophages in vitro and in vivo, leading to intestinal tumour growth in ApcMin/+ mice. Moreover, Fn infection induced high expression of TLR4, IL-6, STAT3, p-STAT3, and c-MYC in cultured macrophages challenged with Fn, which was blocked by TAK-242 pre-treatment (P < 0.05). Interestingly, c-MYC protein was mainly co-localized with CD206+ M2 macrophages with Fn infection. In conclusion, we show that Fn infection increased M2 polarization of macrophages in vitro and in vivo. Furthermore, Fn infection enhanced colorectal tumour growth in a TLR4-dependent manner involving activation of the IL-6/p-STAT3/c-MYC signalling pathway. For the first time, our results indicate an immunosuppressive effect of Fn by promoting M2 polarization of macrophages through a TLR4-dependent mechanism, which may serve as a promising target for immunotherapy of Fn-related CRC.

DNA Methylation Profiling Reveals the Change of Inflammation-Associated ZC3H12D in Leukoaraiosis

Leukoaraiosis (LA) is neuroimaging abnormalities of the cerebral white matter in elderly people. However, the molecular mechanisms underlying the cerebral white matter lesions remain unclear. Here, we reported an epigenetic basis and potential pathogenesis for this complex illness. 317 differentially methylated genes were identified to distinguish the mechanism of occurrence and progression of LA. Gene-Ontology pathway analysis highlighted that those genes with epigenetic changes are mostly involved in four major signaling pathways including inflammation and immune response-associated processes (antigen processing and presentation, T cell costimulation and interferon-γ-mediated signaling pathway), synapse assembly, synaptic transmission and cell adhesion. Moreover, immune response seems to be specific to LA occurrence and subsequent disruption of nervous system functions could drive the progression of LA. The significant change of inflammation-associated ZC3H12D in promoter methylation and mRNA expression was implicated in the occurrence of LA, suggesting its potential functions in the molecular mechanism of LA. Our results suggested that inflammation-associated signaling pathways were involved in the pathogenesis of LA and ZC3H12D may contribute to such inflammatory process underlying LA, and further echoed it as a neuroinflammatory disorder in central nervous system (CNS).

TOX expression decreases with progression of colorectal cancers and is associated with CD4 T-cell density and Fusobacterium nucleatum infection

Fusobacterium nucleatum in the tumor microenvironment plays an important role in the development of colorectal cancer. The underlying mechanism of action, however, remains to be elucidated. We evaluated the relation of F nucleatum amount to thymocyte selection-associated high-mobility group box (TOX) protein expression and CD4⁺ T-cell density in 138 human colorectal tissues. TOX expression and CD4⁺ T-cell density in Fnucleatum-negative tissues were significantly higher compared to those in Fnucleatum-positive tissues (P < .001 and P = .002, respectively). We found a negative correlation between F nucleatum abundance and TOX expression (P < .001) and CD4⁺ T-cell density (P < .001). TOX expression in normal mucosa, hyperplastic polyps, and adenomas was significantly higher than in sessile serrated adenomas and different stages of carcinomas (P < .05). Moreover, CD4⁺ T-cell density in high-TOX expression tissues was significantly higher than in low-TOX expression tissues (P = .003). A positive correlation was found between TOX expression and CD4⁺ T-cell density in colorectal tissues (Spearman correlation coefficient: 0.362, 95% confidence interval: 0.051-0.641, P = .022). Our findings suggest that F nucleatum may suppress antitumor immune responses by decreasing CD4⁺ T-cell density and TOX expression in the progression of colorectal cancer.

Invasive Fusobacterium nucleatum activates beta-catenin signaling in colorectal cancer via a TLR4/P-PAK1 cascade

The underlying mechanism of Fusobacterium nucleatum (Fn) in the carcinogenesis of colorectal cancer (CRC) is poorly understood. Here, we examined Fn abundance in CRC tissues, as well as β-catenin, TLR4 and PAK1 protein abundance in Fn positive and Fn negative CRCs. Furthermore, we isolated a strain of Fn (F01) from a CRC tissue and examined whether Fn (F01) infection of colon cancer cells activated β-catenin signaling via the TLR4/P-PAK1/P-β-catenin S675 cascade. Invasive Fn was abundant in 62.2% of CRC tissues. TLR4, PAK1 and nuclear β-catenin proteins were more abundant within Fn-positive over Fn-negative CRCs (P < 0.05). Fn and its lipopolysaccharide induced a significant increase in TLR4/P-PAK1/P-β-catenin S675/C-myc/CyclinD1 protein abundance, as well as in the nuclear translocation of β-catenin. Furthermore, inhibition of TLR4 or PAK1 prior to challenge with Fn significantly decreased protein abundance of P-β-catenin S675, C-myc and Cyclin D1, as well as nuclear β-catenin accumulation. Inhibition of TLR4 significantly decreased P-PAK1 protein abundance, and for the first time, we observed an interaction between TLR4 and P-PAK1 using immunoprecipitation. Our data suggest that invasive Fn activates β-catenin signaling via a TLR4/P-PAK1/P-β-catenin S675 cascade in CRC. Furthermore, TLR4 and PAK1 could be potential pharmaceutical targets for the treatment of Fn-related CRCs.

Chemopreventive effect of Myricetin, a natural occurring compound, on colonic chronic inflammation and inflammation-driven tumorigenesis in mice

Myricetin is a flavonoids compound extracted from edible myrica rubra. We aimed to evaluate the efficacy of Myricetin on colonic chronic inflammation and inflammation-driven tumorigenesis in mice. Myricetin was administrated by gavage for 4 consecutive weeks. Mice were sacrificed and the number of colonic polyps was counted. Myricetin significantly inhibited AOM/DSS-induced colitis and colorectal tumorigenesis. Myricetin prevented the incidence of colorectal tumorigenesis and reduced the size of colorectal polyps. Histopathologic analysis showed that Myricetin could attenuate the degree of colonic inflammation and colorectal tumorigenesis. Further analysis showed that Myricetin strongly reduced the levels of inflammatory factors TNF-α, IL-1β, IL-6, NF-κB, p-NF-κB, cyclooxygenase-2 (COX-2), PCNA and Cyclin D1 in the colonic tissues as analyzed by the assays of immunohistochemical staining, Western blotting and Q-RT-PCR. Our results demonstrated that Myricetin possesses the biological activities of chemoprevention colonic chronic inflammation and inflammation-driven tumorigenesis. We suggest that Myricetin could be developed as a promising chemopreventive drug for reducing the risk of colorectal cancer.

CBX7 negatively regulates migration and invasion in glioma via Wnt/β-catenin pathway inactivation

CBX7, a member of the Polycomb-group proteins, plays a significant role in normal and cancerous tissues and has been defined as a tumor suppressor in thyroid, breast and pancreatic cancers. However, its function in glioma remains undefined. CBX7 expression is decreased in glioma, especially in higher grade cases, according to data in the CGGA, GSE16001 and TCGA databases. Further experimental evidence has shown that exogenous CBX7 overexpression induced apoptosis and inhibited cell proliferation, colony formation and migration of glioma cells. In this study, we show that the invasive ability of glioma cells was decreased following CBX7 overexpression and CBX7 overexpression was associated with Wnt/β-catenin pathway inhibition, which also decreased downstream expression of ZEB1, a core epithelial-to-mesenchymal transition factor. This reduction in Wnt signaling is controlled by DKK1, a specific Wnt/β-catenin inhibitor. CBX7 enhances DKK1 expression by binding the DKK1 promoter, as shown in Luciferase reporter assays. Our data confirm that CBX7 inhibits EMT and invasion in glioma, which is manifested by influencing the expression of MMP2, MMP9, E-cadherin, N-cadherin and Vimentin in LN229, T98G cells and primary glioma cells (PGC). Furthermore, as a tumor suppressor, CBX7 expression is pivotal to reduce tumor invasion and evaluate prognosis.

The destruction complex of beta-catenin in colorectal carcinoma and colonic adenoma

OBJECTIVE

To evaluate the destruction complex of beta-catenin by the expression of the proteins beta-catetenin, adenomatous polyposis coli, GSK3β, axin and ubiquitin in colorectal carcinoma and colonic adenoma.

METHODS

Tissue samples from 64 patients with colorectal carcinoma and 53 patients with colonic adenoma were analyzed. Tissue microarray blocks and slides were prepared and subjected to immunohistochemistry with polyclonal antibodies in carcinoma, adjacent non-neoplastic mucosa, and adenoma tissues. The immunoreactivity was evaluated by the percentage of positive stained cells and by the intensity assessed through of the stained grade of proteins in the cytoplasm and nucleus of cells. In the statistical analysis, the Spearman correlation coefficient, Student's t, χ2, Mann-Whitney, and McNemar tests, and univariate logistic regression analysis were used.

RESULTS

In colorectal carcinoma, the expressions of beta-catenin and adenomatous polyposis coli proteins were significantly higher than in colonic adenomas (p<0.001 and p<0.0001, respectively). The immunoreactivity of GSK3β, axin 1 and ubiquitin proteins was significantly higher (p=0.03, p=0.039 and p=0.03, respectively) in colorectal carcinoma than in the colonic adenoma and adjacent non-neoplastic mucosa. The immunohistochemistry staining of these proteins did not show significant differences with the clinical and pathological characteristics of colorectal cancer and colonic adenoma.

CONCLUSIONS

These results suggest that, in adenomas, the lower expression of the beta-catenin, axin 1 and GSK3β proteins indicated that the destruction complex of beta-catenin was maintained, while in colorectal carcinoma, the increased expression of beta-catenin, GSK3β, axin 1, and ubiquitin proteins indicated that the destruction complex of beta-catenin was disrupted.

OBJETIVO

Avaliar o complexo de destruição da betacatenina no carcinoma colorretal e no adenoma do colo pela expressão das proteínas betacatenina, adenomatous polyposis coli, GSK3β, axina e ubiquitina.

MÉTODOS

Amostras de tecidos de 64 doentes com carcinoma colorretal e de 53 pacientes com adenoma do colo foram analisadas. Blocos de tecidos foram submetidos ao estudo imuno-histoquímico com anticorpos policlonais nos tecidos do carcinoma, mucosa não neoplásica adjacente e adenoma. A imunorreatividade foi avaliada pela porcentagem de positividade de células coradas e pela intensidade do grau de coloração das proteínas no citoplasma e no núcleo das células. Na análise estatística, foram utilizados o coeficiente de correlação de Spearman, os testes t de Student, χ2, Mann-Whitney e de McNemar, e a análise de regressão logística univariada.

RESULTADOS

No carcinoma colorretal, as expressões da betacatenina e da adenomatous polyposis coli foram significativamente maiores do que em adenomas do colo (p<0,001 e p<0,0001, respectivamente). A imunorreatividade das proteínas GSK3β, axina 1 e ubiquitina foi significativamente maior (p=0,03, p=0,039 e p=0,03, respectivamente) no carcinoma colorretal do que no adenoma e na mucosa não neoplásica adjacente. A coloração imuno-histoquímica dessas proteínas não apresentou diferenças significantes em relação às características clinicopatológicas do câncer colorretal e do adenoma.

CONCLUSÕES

Em adenomas, as menores expressões de betacatenina, axina 1 e GSK3β indicaram que o complexo de destruição da betacatenina estava conservado, enquanto que, no carcinoma colorretal, o aumento das expressões da betacatenina, GSK3β, 1 axina, e ubiquitina indicaram que o complexo de destruição de betacatenina estava alterado.

Conventional colon adenomas harbor various disturbances in microsatellite stability and contain micro-serrated foci with microsatellite instability

Introduction

Colorectal cancer belongs to the most frequent occurring malignancies. A prediction of the clinical outcome and appropriate choice of neoadjuvant chemotherapy needs personalized insight to the main driving pathways. Because most CRCs have polyps as progenitor lesions, studying the pathways driving to adenomagenesis is no less important.

Goals

Our purpose was the evaluation of microsatellite stability status within conventional colon adenomas and also β-catenin, BRAFV600E and p53 contribution.

Material and methods

The cohort included 101 cases of typical colon adenomas with high grade epithelial dysplasia according to WHO. An immunohistochemistry method was used for the depiction of the expression of targeted proteins, as also their heterogeneity.

Results

Generally, we noted a 10% frequency of MSI events where MSI-H reached a 5% share occurred within the left colon and rectal polyps. β-catenin nuclear overexpression was noted with a 70% frequency and p53 with close to a 24% frequency. In addition, we found a presence of micro-serration foci more often within tubular adenomas, where focal MSI took place more often. Our results indicate that MSI events occur more often than had been theorized earlier. It results in tumour heterogeneity, more complex underlying pathways and finally ontogenetic molecular-diversity of tumours besides similar occurring histopathological features.

Invasive Fusobacterium nucleatum may play a role in the carcinogenesis of proximal colon cancer through the serrated neoplasia pathway

The prevalence of invasive Fusobacterium nucleatum (Fn) within the serrated neoplasia pathway of the proximal colon has seldom been investigated. We examined the invasive Fn and bacterial biofilms in 35 proximal hyperplastic polyps (HPs), 33 sessile serrated adenomas (SSAs), 48 proximal colorectal cancers (CRCs) and 10 matched metastatic lymph nodes using 16S rRNA fluorescence in situ hybridization (FISH). Samples of normal mucosa, traditional adenomas (TAs), distal HPs, distal CRCs and matched lymph nodes with or without metastases were used as controls. The prevalence of invasive Fn within proximal HPs (65.7%) and SSAs (78.8%) were significantly higher than that of proximal TAs (28.9%) and distal TAs (24.4%; p < 0.05). Invasive Fn was detected in markedly more proximal CRCs (89.6%) than in distal CRCs (42.2%; p < 0.05). Moreover, invasive Fn was detected in a significantly higher proportion of matched metastatic lymph nodes (100%) than that within nonmetastatic lymph nodes (40.0%; p < 0.001). Bacterial biofilms were found on 52.1% of proximal CRCs, 55.6% of distal CRCs and 48.5% of SSAs. Biofilms were positive for Fn in 47.9% of proximal CRCs, 48.9% of distal CRCs and 27.3% of SSAs. However, the presence of Fn in biofilms was not related to invasive Fn within colorectal tissues (p = 0.415). Invasive Fn may play a role in the carcinogenesis of proximal colon developing via the serrated neoplasia pathway, but might have a less important role in the TA-carcinoma sequence. Bacterial biofilms may not contribute to the invasion of Fn into tumor tissues.

Prognostic significance of survivin, β-catenin and p53 expression in urothelial carcinoma

Survivin, β-catenin, and p53 are well-known cell-cycle and apoptosis regulators of tumorigenesis. Urothelial carcinomas (UCs) are the most common of the human cancers. Compared to superficial tumors (Ta, CIS, or T1), invasive UCs are important with regard to recurrence, progression, and mortality. Therefore, we examined whether survivin, β-catenin, and p53 could be used as the biomarkers for the early prediction of the invasiveness of UCs and the overall survival of the patients. We investigated the prognostic expressions of those biomarkers in UC (n=147) and in non-muscle invasive UC (NMI-UC) (n=113), using tissue microarray and immunohistochemistry. Spearman's correlation analysis and multivariate Cox regression analyses were used for statistical interpretation. High expressions of β-catenin, survivin, and p53 were associated with a high T stage, recurrence, progression, mortality, low recurrence-free survival, low progression-free survival and low overall survival (p <0.01). Similar findings were achieved for recurrence and progression in the NMI-UC group, except for mortality. Moreover, a positive correlation was shown between p53 and β-catenin and between p53 and survivin (r=0.221, p <0.01; r=0.236, p <0.01, respectively). Survivin, p53, and β-catenin overexpression, as prognostic markers, might suggest that the UCs are biologically aggressive with the poor prognosis. Thus, dysregulation of those these cell-cycle and apoptosis regulators in bladder carcinoma could be used as a molecular marker to determine the best treatment strategy and could contribute to the development of targeted therapies.

Distinct WNT/β-catenin signaling activation in the serrated neoplasia pathway and the adenoma-carcinoma sequence of the colorectum

Sessile serrated adenoma/polyp (SSA/P) is considered as an early precursor in the serrated neoplasia pathway leading to colorectal cancer development. The conventional adenoma-carcinoma sequence is associated with activation of the WNT signaling pathway, although its role in serrated lesions is still controversial. To clarify differences in WNT signaling activation in association with MLH1 methylation or BRAF/KRAS mutations between serrated and conventional routes, we performed β-catenin immunostaining, methylation-specific PCR for MLH1 and WNT signaling associated genes such as AXIN2, APC, and MCC and secreted frizzled-related proteins (SFRPs), and direct sequencing of BRAF/KRAS in 27 SSA/Ps, 14 SSA/Ps with high-grade dysplasia and 9 SSA/Ps with submucosal carcinoma, as well as 19 conventional adenomas, 26 adenomas with high-grade dysplasia and 25 adenomas with submucosal carcinoma. Nuclear β-catenin labelings were significantly lower in the serrated series than in their adenoma counterparts, and a significant increment in those labelings was found from SSA/Ps to those with high-grade dysplasia or submucosal carcinoma. The frequency of MLH1 and SFRP4 methylation was significantly higher in SSA/P series, as compared with corresponding adenoma series. AXIN2 and MCC were more frequently methylated in SSA/Ps with high-grade dysplasia and those with submucosal carcinoma than in adenoma counterparts. Stepwise increment of AXIN2 and MCC methylation was identified from SSA/Ps through those with high-grade dysplasia to those with submucosal carcinoma. A significant correlation was seen between nuclear β-catenin expression and methylation of AXIN2 or MCC in the SSA/P series. BRAF mutation was more frequent, whereas KRAS mutation was less frequent in the SSA/P series as compared with the adenoma series. There was an inverse association of BRAF mutation with AXIN2 methylation in SSA/P series. In conclusion, WNT/β-catenin signal activation mediated by the methylation of SFRP4, MCC, and AXIN2 may make different contributions to colorectal neoplasia between the serrated and conventional routes.

Mutated in colorectal cancer (MCC) is a novel oncogene in B lymphocytes

Background

Identification of novel genetic risk factors is imperative for a better understanding of B lymphomagenesis and for the development of novel therapeutic strategies. TRAF3, a critical regulator of B cell survival, was recently recognized as a tumor suppressor gene in B lymphocytes. The present study aimed to identify novel oncogenes involved in malignant transformation of TRAF3-deficient B cells.

Methods

We used microarray analysis to identify genes differentially expressed in TRAF3^−/− mouse splenic B lymphomas. We employed lentiviral vector-mediated knockdown or overexpression to manipulate gene expression in human multiple myeloma (MM) cell lines. We analyzed cell apoptosis and proliferation using flow cytometry, and performed biochemical studies to investigate signaling mechanisms. To delineate protein-protein interactions, we applied affinity purification followed by mass spectrometry-based sequencing.

Results

We identified mutated in colorectal cancer (MCC) as a gene strikingly up-regulated in TRAF3-deficient mouse B lymphomas and human MM cell lines. Aberrant up-regulation of MCC also occurs in a variety of primary human B cell malignancies, including non-Hodgkin lymphoma (NHL) and MM. In contrast, MCC expression was not detected in normal or premalignant TRAF3^−/− B cells even after treatment with B cell stimuli, suggesting that aberrant up-regulation of MCC is specifically associated with malignant transformation of B cells. In elucidating the functional roles of MCC in malignant B cells, we found that lentiviral shRNA vector-mediated knockdown of MCC induced apoptosis and inhibited proliferation in human MM cells. Experiments of knockdown and overexpression of MCC allowed us to identify several downstream targets of MCC in human MM cells, including phospho-ERK, c-Myc, p27, cyclin B1, Mcl-1, caspases 8 and 3. Furthermore, we identified 365 proteins (including 326 novel MCC-interactors) in the MCC interactome, among which PARP1 and PHB2 were two hubs of MCC signaling pathways in human MM cells.

Conclusions

Our results indicate that in sharp contrast to its tumor suppressive role in colorectal cancer, MCC functions as an oncogene in B cells. Our findings suggest that MCC may serve as a diagnostic marker and therapeutic target in B cell malignancies, including NHL and MM.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-014-0056-6) contains supplementary material, which is available to authorized users.

Claudin-1 Expression Is Elevated in Colorectal Cancer Precursor Lesions Harboring the BRAF V600E Mutation

BACKGROUND: Sessile serrated adenomas/polyps (SSA/P) are now recognised precursors of colorectal cancer (CRC) including cancers harbouring somatic BRAF (V600E) mutations. While the morphological diagnostic criteria of SSA/P have been established, distinguishing between small/early SSA/P and microvesicular hyperplastic polyps (MVHP) is challenging and may not be possible in routine practice. METHODS: Gene expression profiling of MVHP (n=5, all BRAF V600E wild-type) and SSA/P (n=5, all BRAF V600E mutant) samples was performed. Quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and immunohistochemical analysis was performed to verify the expression of claudin 1 (CLDN1) in MVHP and SSA/P. RESULTS: Gene expression profiling studies conducted between MVHP and SSA/P identified CLDN1 as the most statistically significant differentially expressed gene (p<0.05). Validation with qRT-PCR confirmed an up-regulation of CLDN1 in BRAF V600E mutant polyps regardless of polyp type (p<0.0005). Immunohistochemical analysis of CLDN1 expression in BRAF V600E mutant SSA/Ps (n=53) and MVHPs (n=111) and BRAF wild-type MVHPs (n=58), demonstrated a strong correlation between CLDN1 expression and the BRAF V600E mutation in both SSA/P and MVHP samples when compared to wild-type polyps (p<0.0001). CONCLUSION: This study demonstrates an up regulation of CLDN1 protein in serrated colorectal polyps including MVHP harbouring the BRAF V600E mutation. Our results demonstrated an apparent heterogeneity on the molecular level within the MVHP group and suggest that MVHP with somatic BRAF V600E mutation and up-regulated expression of CLDN1 are closely related to SSA/P and may in fact represent a continuous spectrum of the same neoplastic process within the serrated pathway of colorectal carcinogenesis.

MCC inhibits beta-catenin transcriptional activity by sequestering DBC1 in the cytoplasm

The mutated in colorectal cancer (MCC) is a multifunctional gene showing loss of expression in colorectal and liver cancers. MCC mutations can drive colon carcinogenesis in the mouse and in vitro experiments suggest that loss of MCC function promotes cancer through several important cellular pathways. In particular, the MCC protein is known to regulate beta-catenin (β-cat) signaling, but the mechanism is poorly understood. Here we show that the β-cat repressor function of MCC is strongly impaired by the presence of a disease-associated mutation. We also identify deleted in breast cancer 1 (DBC1) as a new MCC interacting partner and regulator of β-cat signaling. RNA interference experiments show that DBC1 promotes β-cat transcriptional activity and that the presence of DBC1 is required for MCC-mediated β-cat repression. In contrast to all other DBC1 interacting partners, MCC does not interact through the DBC1 Leucine Zipper domain but with a glutamic-acid rich region located between the Nudix and EF-hand domains. Furthermore, MCC overexpression relocalizes DBC1 from the nucleus to the cytoplasm and reduces β-cat K49 acetylation. Treatment of cells with the SIRT1 inhibitor Nicotinamide reverses MCC-induced deacetylation of β-cat K49. These data suggest that the cytoplasmic MCC-DBC1 interaction sequesters DBC1 away from the nucleus, thereby removing a brake on DBC1 nuclear targets, such as SIRT1. This study provides new mechanistic insights into the DBC1-MCC axis as a new APC independent β-cat inhibitory pathway.

Prevalence and molecular characterisation of the sessile serrated adenoma in a subset of the Chinese population

AIMS

The incidence and mortality rates from right-sided colorectal cancers (CRCs) have not decreased in recent years. It is very likely that a significant proportion of these cancers evolve from undetected sessile serrated adenomas (SSAs). The prevalence and molecular features of the SSAs in the Chinese population have seldom been investigated.

METHODS

We retrospectively reviewed the colonoscopy database and pathology archives in our medical centre. Adenomatous polyposis coli (APC) and β-catenin expressions were examined in 28 right hyperplastic polyps (RHPs) and 21 SSAs by immunohistochemical staining. The mutations of BRAF, KRAS, APC and β-CATENIN were analysed by direct sequencing. The methylation status of APC promoter in these polyps was analysed by methylation-specific PCR and bisulfite sequencing. Samples of left hyperplastic polyps, traditional adenomas and CRC were used as controls.

RESULTS

SSAs accounted for 4.9% of serrated polyps and 1.0% of all colorectal polyps. BRAF((V600E)) mutations were found in 14.3% of SSAs and 7.1% of RHPs. Nuclear accumulation of β-catenin was seen in 28.6% of SSAs and 17.9% of RHPs. APC mutations were detected in 57.1% of SSAs and 67.9% of RHPs. APC methylation was detected in 14.3% of RHPs and 23.8% of SSAs.

CONCLUSIONS

The prevalence of SSAs in a subset of the Chinese population is much lower than that in the Western population. BRAF((V600E)) mutation is not a frequent event in right colon serrated polyps in a subset of the Chinese population. APC mutation is possibly the main cause for the Wnt signalling activation in right colon serrated polyps.

Overexpression of regenerating gene Iα appears to reflect aberration of crypt cell compartmentalization in sessile serrated adenoma/polyps of the colon

Background

Colorectal sessile serrated adenoma/polyps (SSA/Ps) are characterized by asymmetrical distribution of Ki67-positive cells, which varies among crypts and involves the crypt length to a variable extent; the pattern has been designated as aberration of crypt cell compartmentalization. The regenerating gene (REG) Iα is a cell growth and/or anti-apoptotic factor and its overexpression might be associated with aberration of crypt cell compartmentalization in SSA/Ps. We investigated REG Iα expression in SSA/Ps in comparison to hyperplastic polyps (HPs).

Methods

A total of 64 cases of serrated polyps (≥10 mm in size), including 53 SSA/Ps and 11 HPs, were included in the present study. Immunostaining was performed using a labeled streptavidin-biotin method. REG Iα expression was classified as follows: (i) expression of endocrine cells: grade 0 (a few positive cells) to 3 (marked increase in positive cells); (ii) expression of goblet cells: grade 0 (negative) to 2 (positive for crypts and surface epithelial cells); (iii) staining intensity of goblet cells: grade 0 (negative) to 2 (strong); (iv) staining intensity of crypt (absorptive) cell membranes: grade 0 (negative) to 2 (strong). The presence of aberration of crypt cell compartmentalization was assessed using Ki67 immunostaining.

Results

With regard to the REG Iα expression of endocrine cells, 8 out of 11 HPs (73%) were grade 0, whereas 51 of 53 SSA/Ps (96%) were grade 1 or higher (p < 0.001). With regard to the distribution of REG Iα-immunoreactive goblet cells, 10 of 11 HPs (91%) were grade 1, whereas 50 of 53 SSA/Ps (94%) were grade 2 (p < 0.001). A similar trend was found in the staining intensity of goblet cells or crypt cell membranes (p = 0.011). Aberration of crypt cell compartmentalization was more frequently identified in SSA/Ps (72%) than in HPs (18%; p = 0.002). A significant association was observed between REG Iα overexpression and the aberration of crypt cell compartmentalization in serrated polyps (p = 0.037).

Conclusions

REG Iα overexpression is a characteristic of SSA/Ps, which appears to reflect aberration of crypt cell compartmentalization.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7240956081100040