Chromosomal instability by beta-catenin/TCF transcription in APC or beta-catenin mutant cells

Colon cancer transcriptome

Over the last four decades, methodological innovations have continuously changed transcriptome profiling. It is now feasible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples using RNA sequencing (RNA-seq). These transcriptomes serve as a connection between cellular behaviors and their underlying molecular mechanisms, such as mutations. This relationship, in the context of cancer, provides a chance to unravel tumor complexity and heterogeneity and uncover novel biomarkers or treatment options. Since colon cancer is one of the most frequent malignancies, its prognosis and diagnosis seem to be critical. The transcriptome technology is developing for an earlier and more accurate diagnosis of cancer which can provide better protectivity and prognostic utility to medical teams and patients. A transcriptome is a whole set of expressed coding and non-coding RNAs in an individual or cell population. The cancer transcriptome includes RNA-based changes. The combined genome and transcriptome of a patient may provide a comprehensive picture of their cancer, and this information is beginning to affect treatment decision-making in real-time. A full assessment of the transcriptome of colon (colorectal) cancer has been assessed in this review paper based on risk factors such as age, obesity, gender, alcohol use, race, and also different stages of cancer, as well as non-coding RNAs like circRNAs, miRNAs, lncRNAs, and siRNAs. Similarly, they have been examined independently in the transcriptome study of colon cancer.

Role of the WNT/β-catenin/ZKSCAN3 Pathway in Regulating Chromosomal Instability in Colon Cancer Cell lines and Tissues

Zinc finger protein with KRAB and SCAN domains 3 (ZKSCAN3) acts as an oncogenic transcription factor in human malignant tumors, including colon and prostate cancer. However, most of the ZKSCAN3-induced carcinogenic mechanisms remain unknown. In this study, we identified ZKSCAN3 as a downstream effector of the oncogenic Wnt/β-catenin signaling pathway, using RNA sequencing and ChIP analyses. Activation of the Wnt pathway by recombinant Wnt gene family proteins or the GSK inhibitor, CHIR 99021 upregulated ZKSCAN3 expression in a β-catenin-dependent manner. Furthermore, ZKSCAN3 upregulation suppressed the expression of the mitotic spindle checkpoint protein, Mitotic Arrest Deficient 2 Like 2 (MAD2L2) by inhibiting its promoter activity and eventually inducing chromosomal instability in colon cancer cells. Conversely, deletion or knockdown of ZKSCAN3 increased MAD2L2 expression and delayed cell cycle progression. In addition, ZKSCAN3 upregulation by oncogenic WNT/β-catenin signaling is an early event of the adenoma–carcinoma sequence in colon cancer development. Specifically, immunohistochemical studies (IHC) were performed using normal (NM), hyperplastic polyps (HPP), adenomas (AD), and adenocarcinomas (AC). Their IHC scores were considerably different (61.4 in NM; 88.4 in HPP; 189.6 in AD; 246.9 in AC). In conclusion, ZKSCAN3 could be responsible for WNT/β-catenin-induced chromosomal instability in colon cancer cells through the suppression of MAD2L2 expression.

Tcf-1 promotes genomic instability and T cell transformation in response to aberrant β-catenin activation

Understanding the mechanisms promoting chromosomal translocations of the rearranging receptor loci in leukemia and lymphoma remains incomplete. Here we show that leukemias induced by aberrant activation of β-catenin in thymocytes, which bear recurrent Tcra/Myc-Pvt1 translocations, depend on Tcf-1. The DNA double strand breaks (DSBs) in the Tcra site of the translocation are Rag-generated, whereas the Myc-Pvt1 DSBs are not. Aberrantly activated β-catenin redirects Tcf-1 binding to novel DNA sites to alter chromatin accessibility and down-regulate genome-stability pathways. Impaired homologous recombination (HR) DNA repair and replication checkpoints lead to retention of DSBs that promote translocations and transformation of double-positive (DP) thymocytes. The resulting lymphomas, which resemble human T cell acute lymphoblastic leukemia (T-ALL), are sensitive to PARP inhibitors (PARPis). Our findings indicate that aberrant β-catenin signaling contributes to translocations in thymocytes by guiding Tcf-1 to promote the generation and retention of replication-induced DSBs allowing their coexistence with Rag-generated DSBs. Thus, PARPis could offer therapeutic options in hematologic malignancies with active Wnt/β-catenin signaling.

Macrophage orchestration of epithelial and stromal cell homeostasis in the intestine

The intestinal tract is a complex ecosystem where numerous cell types of epithelial, immune, neuronal, and endothelial origin coexist in an intertwined, highly organized manner. The functional equilibrium of the intestine relies heavily on the proper crosstalk and cooperation among each cell population. Furthermore, macrophages are versatile, innate immune cells that participate widely in the modulation of inflammation and tissue remodeling. Emerging evidence suggest that macrophages are central in orchestrating tissue homeostasis. Herein, we describe how macrophages interact with epithelial cells, neurons, and other types of mesenchymal cells under the context of intestinal inflammation, followed by the therapeutic implications of cellular crosstalk pertaining to the treatment of inflammatory bowel disease.

Protein Phosphatase 1 Regulatory Subunit 3: A Prognostic Biomarker in Stomach Adenocarcinoma

Purpose

This study aimed to determine the potential application of the protein phosphatase 1 regulatory subunit 3 (PPP1R3B) gene as a prognostic marker in stomach adenocarcinoma (STAD), as well as its potential mediating biological processes and pathways.

Materials and Methods

Differential expression analyses were performed using the TIMER2.0 and UALCAN databases. Complete RNA-seq data and other relevant clinical and survival data were acquired from The Cancer Genome Atlas (TCGA). Univariate survival analyses, Cox regression modelling, and Kaplan–Meier curves were implemented to investigate the associations between PPP1R3B gene expression and clinical pathologic features. A genome wide gene set enrichment analysis (GSEA) was conducted to define the underlying molecular mechanisms mediating the observed associations between the PPP1R3B gene and STAD development.

Results

We found that PPP1R3B was overexpressed in STAD tissues, and that higher PPP1R3B expression correlated with worse prognoses in patients with STAD. Comprehensive survival analyses suggested that PPP1R3B might be an independent predictive factor for survival time in patients with STAD. The prognostic relationship between PPP1R3B and STAD was also verified using Kaplan–Meier curves. Patients with higher PPP1R3B levels had a shorter clinical survival time on average. Additionally, a GSEA demonstrated that PPP1R3B might be involved in multiple biological processes and pathways.

Conclusion

Our findings demonstrate that the PPP1R3B gene has utility as a potential molecular marker for STAD prognoses.

Phosphorylation of β-catenin Ser60 by polo-like kinase 1 drives the completion of cytokinesis

β-Catenin is a multifunctional protein and participates in numerous processes required for embryonic development, cell proliferation, and homeostasis through various molecular interactions and signaling pathways. To date, however, there is no direct evidence that β-catenin contributes to cytokinesis. Here, we identify a novel p-S60 epitope on β-catenin generated by Plk1 kinase activity, which can be found at the actomyosin contractile ring of early telophase cells and at the midbody of late telophase cells. Depletion of β-catenin leads to cytokinesis-defective phenotypes, which eventually result in apoptotic cell death. In addition, phosphorylation of β-catenin Ser60 by Plk1 is essential for the recruitment of Ect2 to the midbody, activation of RhoA, and interaction between β-catenin, Plk1, and Ect2. Time-lapse image analysis confirmed the importance of β-catenin phospho-Ser60 in furrow ingression and the completion of cytokinesis. Taken together, we propose that phosphorylation of β-catenin Ser60 by Plk1 in cooperation with Ect2 is essential for the completion of cytokinesis. These findings may provide fundamental knowledge for the research of cytokinesis failure-derived human diseases.

Regulation of signal transduction pathways in colorectal cancer: implications for therapeutic resistance

Resistance to anti-cancer treatments is a critical and widespread health issue that has brought serious impacts on lives, the economy and public policies. Mounting research has suggested that a selected spectrum of patients with advanced colorectal cancer (CRC) tend to respond poorly to both chemotherapeutic and targeted therapeutic regimens. Drug resistance in tumours can occur in an intrinsic or acquired manner, rendering cancer cells insensitive to the treatment of anti-cancer therapies. Multiple factors have been associated with drug resistance. The most well-established factors are the emergence of cancer stem cell-like properties and overexpression of ABC transporters that mediate drug efflux. Besides, there is emerging evidence that signalling pathways that modulate cell survival and drug metabolism play major roles in the maintenance of multidrug resistance in CRC. This article reviews drug resistance in CRC as a result of alterations in the MAPK, PI3K/PKB, Wnt/β-catenin and Notch pathways.

Studying the Role of Chromosomal Instability (CIN) in GI Cancers Using Patient-derived Organoids

Chromosomal instability (CIN) is associated with the initiation and progression of gastrointestinal (GI) tract cancers. Cancers of the GI tract are typically characterized by altered chromosome numbers. While the dynamics of CIN have been extensively characterized in 2D monolayer cell cultures derived from GI tumors, the tumor microenvironment and 3D tumor architecture also contribute to the progression of CIN, which is not captured in 2D cell culture systems. To overcome these limitations, self-organizing cellular structures that retain organ-specific 3D architecture, namely organoids, have been derived from various tissues of the GI tract. Organoids derived from normal tissue and patient tumors serve as a useful paradigm to study the crosstalk between tumor cells in the context of a tissue microenvironment and its impact on chromosomal stability. Such a paradigm, therefore, has a considerable advantage over 2D cell culture systems in drug screening and personalized medicine. Here, we review the importance of patient-derived tumor organoids (PDTOs) as a model to study CIN in cancers of the GI tract.

Secreted Frizzled-Related Protein 4 (SFRP4) Is an Independent Prognostic Marker in Prostate Cancers Lacking TMPRSS2: ERG Fusions

Secreted frizzled-related protein 4 (SFRP4) controls WNT signaling and is thought to play a role for tumor aggressiveness. Here, we analyzed a tissue microarray containing 11,152 prostate cancers with pathological, clinical and molecular data by immunohistochemistry. SFRP4 expression was higher in cancer than in non-neoplastic acinar cells. SFRP4 staining was seen in 64.9% of tumors and classified as weak in 33.2%, moderate in 23.9% and strong in 7.8% of cancers. SFRP4 overexpression was linked to advanced tumor stage, high classical/quantitative Gleason grade (p < 0.0001 each), lymph node metastasis (p = 0.0002), and a positive surgical margin (p = 0.0017). SFRP4 positivity was markedly more frequent in ERG positive (77.4%) than in ERG negative cancers (57.4% p < 0.0001). Subset analyses in 2725 cancers with and 3592 cancers without TMPRSS2:ERG fusion revealed that associations with tumor phenotype and patient outcome were largely driven by the subset of ERG negative tumors. In a multivariate analysis including various postoperative and prognostic clinico-pathological features, SFRP4 protein expression emerged as an independent prognostic parameter in ERG negative cancers. SFRP4 immunostaining was significantly linked with 10 of 11 previously analyzed chromosomal deletions (p < 0.05 each). In conclusion, high SFRP4 immunostaining is associated with poor prognosis and genomic instability in ERG negative prostate cancers.

Activation of Epithelial-Mesenchymal Transition and Altered β-Catenin Signaling in a Novel Indian Colorectal Carcinoma Cell Line

Colorectal cancer is the third major cause of cancer-related mortality worldwide. The upward trend in incidence and mortality rates, poor sensitivity to conventional therapies and a dearth of early diagnostic parameters pose a huge challenge in the management of colorectal cancer in India. Due to the high level of genetic diversity present in the Indian population, unraveling the genetic contributions toward pathogenesis is key for understanding the etiology of colorectal cancer and in reversing this trend. We have established a novel cell line, MBC02, from an Indian colorectal cancer patient and have carried out extensive molecular characterization to unravel the pathological alterations in this cell line. In-depth molecular analysis of MBC02 revealed suppression of E-cadherin expression, concomitant with overexpression of EMT related molecules, which manifested in the form of highly migratory and invasive cells. Loss of membrane-tethered E-cadherin released β-catenin from the adherens junction resulting in its cytoplasmic and nuclear accumulation and consequently, upregulation of c-Myc. MBC02 also showed dramatic transcriptional upregulation of β-catenin. Remarkably, we observed significantly elevated proteasome activity that perhaps co-evolved to compensate for the unnaturally high mRNA level of β-catenin to regulate the increased protein load. In addition, there was substantial misregulation of other clinically relevant signaling pathways that have clinical relevance in the pathogenesis of colorectal cancer. Our findings pave the way toward understanding the molecular differences that could define pathogenesis in cancers originating in the Indian population.

Overview of the oncogenic signaling pathways in colorectal cancer: Mechanistic insights

Colorectal cancer is a multifaceted disease which is therapeutically challenging. Based on insights gleaned from almost a quarter century of research, it is obvious that deregulation of spatio-temporally controlled signaling pathways play instrumental role in development and progression of colorectal cancer. High-throughput technologies have helped to develop a sharper and broader understanding of the wide ranging signal transduction cascades which also contribute to development of drug resistance, loss of apoptosis and, ultimately, of metastasis. In this review, we have set the spotlight on role of JAK/STAT, TGF/SMAD, Notch, WNT/β-Catenin, SHH/GLI and p53 pathways in the development and progression of colorectal cancer. We have also highlighted recent reports on TRAIL-mediated pathways and molecularly distinct voltage-gated sodium channels in colorectal cancer.

Multiple oncogenic roles of nuclear beta-catenin

β-Catenin is essential for embryonic development and required for cell renewal/regeneration in adult life. Cellular β-catenin exists in three different pools: membranous, cytoplasmic and nuclear. In this review, we focus on functions of the nuclear pool in relation to tumorigenesis. In the nucleus, beta-catenin functions as both activator and repressor of transcription in a context-dependent manner. It promotes cell proliferation and supports tumour growth by enhancing angiogenesis. β-Catenin-mediated signalling regulates cancer cell metabolism and is associated with tumour-initiating cells in multiple malignancies. In addition, it functions as both pro- and anti-apoptotic factor besides acting to inhibit recruitment of inflammatory anti-tumour T-cells. Thus, β-catenin appears to possess a multifaceted nuclear function that may significantly impact tumour initiation and progression.

Modeling APC mutagenesis and familial adenomatous polyposis using human iPS cells

Mutations in the gene Adenomatous Polyposis Coli or APC appear in most sporadic cases of colorectal cancer and it is the most frequent mutation causing hereditary Familial Adenomatous Polyposis. The detailed molecular mechanism by which APC mutations predispose to the development of colorectal cancer is not completely understood. This is in part due to the lack of accessibility to appropriate models that recapitulate the early events associated with APC mediated intestinal transformation. We have established a novel platform utilizing human induced Pluripotent Stem cells or iPSC from normal or FAP-specific APC mutant individuals and evaluated the effect of the mutation in the cells before and after differentiation into intestinal organoids. In order to minimize genetic background effects, we also established an isogenic platform using TALEN-mediated gene editing. Comparison of normal and APC mutant iPSC revealed a significant defect in cell identity and polarity due to the presence of APC in heterozygosity as well as chromosomal aberrations including abnormal anaphases and centrosome numbers. Importantly, upon specification into intestinal progeny, APC heterozygosity was responsible for a major change in the transcriptional identity of the cells with dysregulation of key signaling pathways, including metabolic reprogramming, abnormal lipid metabolism and intestinal-specific cadherin expression. In conclusion, we have developed a novel iPSC/intestinal model of APC mutagenesis and provide strong evidence that APC in heterozygosity imparts a clear phenotypic and molecular defect, affecting basic cellular functions and integrity, providing novel insights in the earlier events of APC-mediated tumorigenesis.

The Progress of T Cell Immunity Related to Prognosis in Gastric Cancer

Gastric cancer is the fifth most common malignancy all over the world, and the factors that can affect progress and prognosis of the gastric cancer patients are various, such as TNM stages, invasive depth, and lymph node metastasis ratio. T cell immunity is important component of human immunity system and immunity responding to tumor and dysfunction or imbalance of T cell immunity will lead to serious outcomes for body. T cell immunity includes many different types of cells, CD4+ T cell, CD8+ T cell, memory cell, and so on, and each of them has special function on antitumor response or tumor immune escape which is revealed in lung cancer, colorectal cancer, breast cancer, ovarian cancer, and so on. But its correlation with gastric cancer is not clear. Our review was preformed to explore the relationship between the progress and prognosis of gastric cancer (GC) and T cell immunity. According to recent researches, T cell immunity may have an important role in the progress and prognosis of GCs, but its function is affected by location, category, related molecule, and interaction between the cells, and some effects still are controversial. More researches are needed to clarify this correlation.

Germline mutation contribution to chromosomal instability

Genomic instability is a feature of cancer that fuels oncogenesis through increased frequency of genetic disruption, leading to loss of genomic integrity and promoting clonal evolution as well as tumor transformation. A form of genomic instability prevalent across cancer types is chromosomal instability, which involves karyotypic changes including chromosome copy number alterations as well as gross structural abnormalities such as transversions and translocations. Defects in cellular mechanisms that are in place to govern fidelity of chromosomal segregation, DNA repair and ultimately genomic integrity are known to contribute to chromosomal instability. In this review, we discuss the association of germline mutations in these pathways with chromosomal instability in the background of related cancer predisposition syndromes. We will also reflect on the impact of genetic predisposition to clinical management of patients and how we can exploit this vulnerability to promote catastrophic genomic instability as a therapeutic strategy.

TTK Inhibitors as a Targeted Therapy for CTNNB1 (-catenin) Mutant Cancers

The spindle assembly checkpoint kinase TTK (Mps1) is a key regulator of chromosome segregation and is the subject of novel targeted therapy approaches by small-molecule inhibitors. Although the first TTK inhibitors have entered phase I dose escalating studies in combination with taxane chemotherapy, a patient stratification strategy is still missing. With the aim to identify a genomic biomarker to predict the response of tumor cells to TTK inhibitor therapy, we profiled a set of preclinical and clinical TTK inhibitors from different chemical series on a panel of 66 genetically characterized cell lines derived from different tumors (Oncolines). Cell lines harboring activating mutations in the CTNNB1 gene, encoding the Wnt pathway signaling regulator β-catenin, were on average up to five times more sensitive to TTK inhibitors than cell lines wild-type for CTNNB1 The association of CTNNB1-mutant status and increased cancer cell line sensitivity to TTK inhibition was confirmed with isogenic cell line pairs harboring either mutant or wild-type CTNNB1 Treatment of a xenograft model of a CTNNB1-mutant cell line with the TTK inhibitor NTRC 0066-0 resulted in complete inhibition of tumor growth. Mutations in CTNNB1 occur at relatively high frequency in endometrial cancer and hepatocellular carcinoma, which are known to express high TTK levels. We propose mutant CTNNB1 as a prognostic drug response biomarker, enabling the selection of patients most likely to respond to TTK inhibitor therapy in proof-of-concept clinical trials. Mol Cancer Ther; 16(11); 2609-17. ©2017 AACR.

Nuclear α-catenin mediates the DNA damage response via β-catenin and nuclear actin

α-Catenin is an F-actin-binding protein widely recognized for its role in cell-cell adhesion. However, a growing body of literature indicates that α-catenin is also a nuclear protein. In this study, we show that α-catenin is able to modulate the sensitivity of cells to DNA damage and toxicity. Furthermore, nuclear α-catenin is actively recruited to sites of DNA damage. This recruitment occurs in a β-catenin-dependent manner and requires nuclear actin polymerization. These findings provide mechanistic insight into the WNT-mediated regulation of the DNA damage response and suggest a novel role for the α-catenin-β-catenin complex in the nucleus.

Wnt signaling in cancer

Wnt signaling is one of the key cascades regulating development and stemness, and has also been tightly associated with cancer. The role of Wnt signaling in carcinogenesis has most prominently been described for colorectal cancer, but aberrant Wnt signaling is observed in many more cancer entities. Here, we review current insights into novel components of Wnt pathways and describe their impact on cancer development. Furthermore, we highlight expanding functions of Wnt signaling for both solid and liquid tumors. We also describe current findings how Wnt signaling affects maintenance of cancer stem cells, metastasis and immune control. Finally, we provide an overview of current strategies to antagonize Wnt signaling in cancer and challenges that are associated with such approaches.

Autocrine Wnt regulates the survival and genomic stability of embryonic stem cells

Wnt signaling plays an important role in the self-renewal and differentiation of stem cells. The secretion of Wnt ligands requires Evi (also known as Wls). Genetically ablating Evi provides an experimental approach to studying the consequence of depleting all redundant Wnt proteins, and overexpressing Evi enables a nonspecific means of increasing Wnt signaling. We generated Evi-deficient and Evi-overexpressing mouse embryonic stem cells (ESCs) to analyze the role of autocrine Wnt production in self-renewal and differentiation. Self-renewal was reduced in Evi-deficient ESCs and increased in Evi-overexpressing ESCs in the absence of leukemia inhibitory factor, which supports the self-renewal of ESCs. The differentiation of ESCs into cardiomyocytes was enhanced when Evi was overexpressed and teratoma formation and growth of Evi-deficient ESCs in vivo were impaired, indicating that autocrine Wnt ligands were necessary for ESC differentiation and survival. ESCs lacking autocrine Wnt signaling had mitotic defects and showed genomic instability. Together, our study demonstrates that autocrine Wnt secretion is important for the survival, chromosomal stability, differentiation, and tumorigenic potential of ESCs.

Important molecular genetic markers of colorectal cancer

Colorectal cancer (CRC) ranks third in the incidences of cancer morbidity and mortality worldwide. CRC is rather heterogeneous with regard to molecular genetic characteristics and pathogenic pathways. A wide spectrum of biomarkers is used for molecular subtype determination, prognosis, and estimation of sensitivity to different drugs in practice. These biomarkers can include germline and somatic mutations, chromosomal aberrations, genomic abnormalities, gene expression alterations at mRNA or protein level and changes in DNA methylation status. In the present review we discuss the most important and well-studied CRC biomarkers, and their potential clinical significance and current approaches to molecular classification of colorectal tumors.

Genetic heterogeneity in cholangiocarcinoma: a major challenge for targeted therapies

Cholangiocarcinoma (CC) encompasses a group of related but distinct malignancies whose lack of a stereotyped genetic signature makes challenging the identification of genomic landscape and the development of effective targeted therapies.

Accumulated evidences strongly suggest that the remarkable genetic heterogeneity of CC may be the result of a complex interplay among different causative factors, some shared by most human cancers while others typical of this malignancy.

Currently, considerable efforts are ongoing worldwide for the genetic characterization of CC, also using advanced technologies such as next-generation sequencing (NGS). Undoubtedly this technology could offer an unique opportunity to broaden our understanding on CC molecular pathogenesis. Despite this great potential, however, the high complexity in terms of factors potentially contributing to genetic variability in CC calls for a more cautionary application of NGS to this malignancy, in order to avoid possible biases and criticisms in the identification of candidate actionable targets. This approach is further justified by the urgent need to develop effective targeted therapies in this disease.

A multidisciplinary approach integrating genomic, functional and clinical studies is therefore mandatory to translate the results obtained by NGS into effective targeted therapies for this orphan disease.

Analysis of APC mutation in human ameloblastoma and clinical significance

As a highly conserved signaling pathway, Wnt/β-catenin signal transduction pathway plays an important role in many processes. Either in the occurrence or development of tumor, activation of this pathway takes an important place. APC inhibits Wnt/β-catenin pathway to regulate cell proliferation and differentiation. This study aimed to investigate the function of cancer suppressor gene. PCR amplification and sequencing method was used to analyze APC mutations of human clinical specimens. The pathological specimens were collected for PCR and clear electrophoretic bands were obtained after electrophoresis. The gene sequence obtained after purification and sequencing analysis was compared with the known APC gene sequence (NM_000038.5). Base mutations at APC 1543 (T → C), APC-4564 (G → A), APC-5353 (T → G), APC-5550 (T → A) and APC-5969 (G → A) locus existed in 22 (27.5 %), 12 (15 %), 5 (6.25 %), 13 (16.25 %) and 12 patients (15 %), respectively. Gene mutations existed in ameloblastoma, and the mutation loci were 1543 locus (T → C), 4564 locus (G → A), 5353 locus (T → G), 5550 locus (T → A) and 5969 locus (G → A) 15 %, respectively. APC mutation plays a certain role in monitoring the tumor malignant degree as it may indicate the transition process of ameloblastoma malignant phenotype.

Pathogenesis of cholangiocarcinoma: From genetics to signalling pathways

Cholangiocarcinoma (CCA) is a malignant tumour of bile duct epithelial cells with dismal prognosis and rising incidence. Chronic inflammation resulting from liver fluke infection, hepatitis and other inflammatory bowel diseases is a major contributing factor to cholangiocarcinogenesis, likely through accumulation of serial genetic and epigenetic alterations resulting in aberration of oncogenes and tumour suppressors. Recent studies making use of advances in high-throughput genomics have revealed the genetic landscape of CCA, greatly increasing our understanding of its underlying biology. A series of highly recurrent mutations in genes such as TP53, KRAS, SMAD4, BRAF, MLL3, ARID1A, PBRM1 and BAP1, which are known to be involved in cell cycle control, cell signalling pathways and chromatin dynamics, have led to investigations of their roles, through molecular to mouse modelling studies, in cholangiocarcinogenesis. This review focuses on the landscape genetic alterations in CCA and its functional relevance to the formation and progression of CCA.

Time course of the incidence/multiplicity and histopathological features of murine colonic dysplasia, adenoma and adenocarcinoma induced by benzo[a]pyrene and dextran sulfate sodium

Benzo[a]pyrene (BP) is mutagenic but noncarcinogenic in the murine colon. Recently, we reported rapid induction of colonic tumors by treatment of CD2F₁ mice with BP (125 mg/kg for 5 days) followed by a colitis inducer, dextran sulfate sodium (DSS) (4% in drinking water for 1 or 2 weeks). However, there are no reports on detailed time course and histopathological features of colonic proliferative lesions in this model. Here, we show the detailed time course of colonic dysplasia, adenoma and adenocarcinoma induced by treatment with BP, DSS, and a combination of the two (BP/DSS). In the colon of mice exposed to BP/DSS, 14.6 dysplastic foci per mouse were present one week after DSS treatment (week 4). The number of dysplastic foci decreased with time to 3.1 at week 9 and thereafter remained almost constant. At week 4, 1.5 adenocarcinomas were also observed, with a marked increase in numbers with time, reaching 29.3 at week 14. In contrast, the number of dysplastic foci induced by DSS alone showed a time course similar to that following BP/DSS treatment; however, only a few tumors appeared. Neither dysplastic foci nor neoplastic lesions were induced by BP only. In mice exposed to BP/DSS, β-catenin was demonstrated immunohistochemically in the nucleus and/or cytoplasm of the tumor cells, and this translocation from the cell membrane was evident in subsets of dysplastic foci. In dysplastic foci induced by DSS alone, β-catenin was absent in the nucleus/cytoplasm. These finding suggest that aberrant β-catenin accumulation in dysplastic foci is associated with tumor progression in this BP/DSS model.

A rare human syndrome provides genetic evidence that WNT signaling is required for reprogramming of fibroblasts to induced pluripotent stem cells

WNT signaling promotes the reprogramming of somatic cells to an induced pluripotent state. We provide genetic evidence that WNT signaling is a requisite step during the induction of pluripotency. Fibroblasts from individuals with focal dermal hypoplasia (FDH), a rare genetic syndrome caused by mutations in the essential WNT processing enzyme PORCN, fail to reprogram with standard methods. This blockade in reprogramming is overcome by ectopic WNT signaling and PORCN overexpression, thus demonstrating that WNT signaling is essential for reprogramming. The rescue of reprogramming is critically dependent on the level of WNT signaling: steady baseline activation of the WNT pathway yields karyotypically normal iPSCs, whereas daily stimulation with Wnt3a produces FDH-iPSCs with severely abnormal karyotypes. Therefore, although WNT signaling is required for cellular reprogramming, inappropriate activation of WNT signaling induces chromosomal instability, highlighting the precarious nature of ectopic WNT activation and its tight relationship with oncogenic transformation.

Apc and p53 interaction in DNA damage and genomic instability in hepatocytes

Disruption of Apc within hepatocytes activates Wnt signaling, perturb differentiation and ultimately lead to neoplasia. Apc negatively regulates Wnt signaling but is also involved in organizing the cytoskeleton and may play a role in chromosome segregation. In vitro studies have implicated Apc in the control of genomic stability. However, the relevance of this data has been questioned in vivo as Apc is lost earlier than the onset of genomic instability. Here, we analyse the relationship between immediate loss of Apc and the acquisition of genomic instability in hepatocytes. We used Cre-lox technology to inactivate Apc and in combination with p53 in vivo, to define the consequences of gene loss upon cell-cycle regulation, proliferation, death and aneuploidy. We show that whilst Apc loss leads to increased proliferation, it also leads to increased apoptosis, the accumulation of p53, p21 and markers of DSBs and DNA repair. Flow cytometry revealed an increased 4N DNA content, consistent with a G2 arrest. Levels of anaphase bridges were also elevated, implicating failed chromosome segregation. This was accompanied by an increase in centrosome number which demonstrates a role for Apc in maintaining euploidy.

To address the role of p53 in these processes, we analyzed combined loss of Apc and p53, which led to a further increase in proliferation, cell death, DNA damages and repair and a bypass of G2 arrest than was observed with Apc loss. However we observed only a marginal effect on anaphase bridges and centrosome number which could be due to increased cell death. Our data therefore establishes, in an in vivo setting, that APC loss leads to a DNA damage signature and genomic instability in the liver and that additional loss of p53 leads to an increase in the DNA damage signal but not to an immediate increase in the genomic instability phenotype.

Enrichment of the β-catenin-TCF complex at the S and G2 phases ensures cell survival and cell cycle progression

Wnt-β-catenin (β-catenin is also known as CTNNB1 in human) signaling through the β-catenin-TCF complex plays crucial roles in tissue homeostasis. Wnt-stimulated β-catenin-TCF complex accumulation in the nucleus regulates cell survival, proliferation and differentiation through the transcription of target genes. Compared with their levels in G1, activation of the receptor LRP6 and cytosolic β-catenin are both upregulated in G2 cells. However, accumulation of the Wnt pathway negative regulator AXIN2 also occurs in this phase. Therefore, it is unclear whether Wnt signaling is active in G2 phase cells. Here, we established a bimolecular fluorescence complementation (BiFC) biosensor system for the direct visualization of the β-catenin-TCF interaction in living cells. Using the BiFC biosensor and co-immunoprecipitation experiments, we demonstrate that levels of the nucleus-localized β-catenin-TCF complex increase during the S and G2 phases, and declines in the next G1 phase. Accordingly, a subset of Wnt target genes is transcribed by the β-catenin-TCF complex during both the S and G2 phases. By contrast, transient inhibition of this complex disturbs both cell survival and G2/M progression. Our results suggest that in S and G2 phase cells, Wnt-β-catenin signaling is highly active and functions to ensure cell survival and cell cycle progression.

APC2 and Axin promote mitotic fidelity by facilitating centrosome separation and cytoskeletal regulation

To ensure the accurate transmission of genetic material, chromosome segregation must occur with extremely high fidelity. Segregation errors lead to chromosomal instability (CIN), with deleterious consequences. Mutations in the tumor suppressor adenomatous polyposis coli (APC) initiate most colon cancers and have also been suggested to promote disease progression through increased CIN, but the mechanistic role of APC in preventing CIN remains controversial. Using fly embryos as a model, we investigated the role of APC proteins in CIN. Our findings suggest that APC2 loss leads to increased rates of chromosome segregation error. This occurs through a cascade of events beginning with incomplete centrosome separation leading to failure to inhibit formation of ectopic cleavage furrows, which result in mitotic defects and DNA damage. We test several hypotheses related to the mechanism of action of APC2, revealing that APC2 functions at the embryonic cortex with several protein partners, including Axin, to promote mitotic fidelity. Our in vivo data demonstrate that APC2 protects genome stability by modulating mitotic fidelity through regulation of the cytoskeleton.

CCAT2, a novel noncoding RNA mapping to 8q24, underlies metastatic progression and chromosomal instability in colon cancer

The functional roles of SNPs within the 8q24 gene desert in the cancer phenotype are not yet well understood. Here, we report that CCAT2, a novel long noncoding RNA transcript (lncRNA) encompassing the rs6983267 SNP, is highly overexpressed in microsatellite-stable colorectal cancer and promotes tumor growth, metastasis, and chromosomal instability. We demonstrate that MYC, miR-17-5p, and miR-20a are up-regulated by CCAT2 through TCF7L2-mediated transcriptional regulation. We further identify the physical interaction between CCAT2 and TCF7L2 resulting in an enhancement of WNT signaling activity. We show that CCAT2 is itself a WNT downstream target, which suggests the existence of a feedback loop. Finally, we demonstrate that the SNP status affects CCAT2 expression and the risk allele G produces more CCAT2 transcript. Our results support a new mechanism of MYC and WNT regulation by the novel lncRNA CCAT2 in colorectal cancer pathogenesis, and provide an alternative explanation of the SNP-conferred cancer risk.

β-catenin at the centrosome: discrete pools of β-catenin communicate during mitosis and may co-ordinate centrosome functions and cell cycle progression

Beta-catenin is a multifunctional protein with critical roles in cell-cell adhesion, Wnt-signaling and the centrosome cycle. Whereas the roles of β-catenin in cell-cell adhesion and Wnt-signaling have been studied extensively, the mechanism(s) involving β-catenin in centrosome functions are poorly understood. β-Catenin localizes to centrosomes and promotes mitotic progression. NIMA-related protein kinase 2 (Nek2), which stimulates centrosome separation, binds to and phosphorylates β-catenin. β-Catenin interacting proteins involved in Wnt signaling such as adenomatous polyposis coli, Axin, and GSK3β, are also localized at centrosomes and play roles in promoting mitotic progression. Additionally, proteins associated with cell-cell adhesion sites, such as dynein, regulate mitotic spindle positioning. These roles of proteins at the cell cortex and Wnt signaling that involve β-catenin indicate a cross-talk between different sub-cellular sites in the cell at mitosis, and that different pools of β-catenin may co-ordinate centrosome functions and cell cycle progression.

CCAT2, a novel noncoding RNA mapping to 8q24, underlies metastatic progression and chromosomal instability in colon cancer

The functional roles of SNPs within the 8q24 gene desert in the cancer phenotype are not yet well understood. Here, we report that CCAT2, a novel long noncoding RNA transcript (lncRNA) encompassing the rs6983267 SNP, is highly overexpressed in microsatellite-stable colorectal cancer and promotes tumor growth, metastasis, and chromosomal instability. We demonstrate that MYC, miR-17-5p, and miR-20a are up-regulated by CCAT2 through TCF7L2-mediated transcriptional regulation. We further identify the physical interaction between CCAT2 and TCF7L2 resulting in an enhancement of WNT signaling activity. We show that CCAT2 is itself a WNT downstream target, which suggests the existence of a feedback loop. Finally, we demonstrate that the SNP status affects CCAT2 expression and the risk allele G produces more CCAT2 transcript. Our results support a new mechanism of MYC and WNT regulation by the novel lncRNA CCAT2 in colorectal cancer pathogenesis, and provide an alternative explanation of the SNP-conferred cancer risk.

Immune response profiling identifies autoantibodies specific to Moyamoya patients

Background

Moyamoya Disease is a rare, devastating cerebrovascular disorder characterized by stenosis/occlusion of supraclinoid internal carotid arteries and development of fragile collateral vessels. Moyamoya Disease is typically diagnosed by angiography after clinical presentation of cerebral hemorrhage or ischemia. Despite unclear etiology, previous reports suggest there may be an immunological component.

Methods

To explore the role of autoimmunity in moyamoya disease, we used high-density protein arrays to profile IgG autoantibodies from the sera of angiographically-diagnosed Moyamoya Disease patients and compared these to healthy controls. Protein array data analysis followed by bioinformatics analysis yielded a number of auto-antibodies which were further validated by ELISA for an independent group of MMD patients (n = 59) and control patients with other cerebrovascular diseases including carotid occlusion, carotid stenosis and arteriovenous malformation.

Results

We identified 165 significantly (p < 0.05) elevated autoantibodies in Moyamoya Disease, including those against CAMK2A, CD79A and EFNA3. Pathway analysis associated these autoantibodies with post-translational modification, neurological disease, inflammatory response, and DNA damage repair and maintenance. Using the novel functional interpolating single-nucleotide polymorphisms bioinformatics approach, we identified 6 Moyamoya Disease-associated autoantibodies against APP, GPS1, STRA13, CTNNB1, ROR1 and EDIL3. The expression of these 6 autoantibodies was validated by custom-designed reverse ELISAs for an independent group of Moyamoya Disease patients compared to patients with other cerebrovascular diseases.

Conclusions

We report the first high-throughput analysis of autoantibodies in Moyamoya Disease, the results of which may provide valuable insight into the immune-related pathology of Moyamoya Disease and may potentially advance diagnostic clinical tools.

Genetic instability: tipping the balance

Tumor cells typically contain a genome that is highly divergent from the genome of normal, non-transformed cells. This genetic divergence is caused by a number of distinct changes that the tumor cell acquires during its transformation from a normal cell into a tumorigenic counterpart. Changes to the genome include mutations, deletions, insertions, and also gross chromosomal aberrations, such as chromosome translocations and whole chromosome gains or losses. This genetic disorder of the tumor cell has complicated the identification of crucial driver mutations that cause cancer. Moreover, the large genetic divergence between different tumors causes them to behave very differently, and makes it difficult to predict response to therapy. In addition, tumor cells are genetically unstable and frequently acquire new mutations and/or gross chromosomal aberrations as they divide. This is beneficial for the overall capacity of a tumor to adapt to changes in its environment, but newly acquired genetic alterations can also compromise the genetic dominance of the tumor cell and thus affect tumor cell viability. Here, we review the mechanisms that can cause gross chromosomal aberrations, and discuss how these affect tumor cell viability.

Genome-wide profiling of pluripotent cells reveals a unique molecular signature of human embryonic germ cells

Human embryonic germ cells (EGCs) provide a powerful model for identifying molecules involved in the pluripotent state when compared to their progenitors, primordial germ cells (PGCs), and other pluripotent stem cells. Microarray and Principal Component Analysis (PCA) reveals for the first time that human EGCs possess a transcription profile distinct from PGCs and other pluripotent stem cells. Validation with qRT-PCR confirms that human EGCs and PGCs express many pluripotency-associated genes but with quantifiable differences compared to pluripotent embryonic stem cells (ESCs), induced pluripotent stem cells (IPSCs), and embryonal carcinoma cells (ECCs). Analyses also identified a number of target genes that may be potentially associated with their unique pluripotent states. These include IPO7, MED7, RBM26, HSPD1, and KRAS which were upregulated in EGCs along with other pluripotent stem cells when compared to PGCs. Other potential target genes were also found which may contribute toward a primed ESC-like state. These genes were exclusively up-regulated in ESCs, IPSCs and ECCs including PARP1, CCNE1, CDK6, AURKA, MAD2L1, CCNG1, and CCNB1 which are involved in cell cycle regulation, cellular metabolism and DNA repair and replication. Gene classification analysis also confirmed that the distinguishing feature of EGCs compared to ESCs, ECCs, and IPSCs lies primarily in their genetic contribution to cellular metabolism, cell cycle, and cell adhesion. In contrast, several genes were found upregulated in PGCs which may help distinguish their unipotent state including HBA1, DMRT1, SPANXA1, and EHD2. Together, these findings provide the first glimpse into a unique genomic signature of human germ cells and pluripotent stem cells and provide genes potentially involved in defining different states of germ-line pluripotency.

Exome sequencing of liver fluke-associated cholangiocarcinoma

Opisthorchis viverrini-related cholangiocarcinoma (CCA), a fatal bile duct cancer, is a major public health concern in areas endemic for this parasite. We report here whole-exome sequencing of eight O. viverrini-related tumors and matched normal tissue. We identified and validated 206 somatic mutations in 187 genes using Sanger sequencing and selected 15 genes for mutation prevalence screening in an additional 46 individuals with CCA (cases). In addition to the known cancer-related genes TP53 (mutated in 44.4% of cases), KRAS (16.7%) and SMAD4 (16.7%), we identified somatic mutations in 10 newly implicated genes in 14.8-3.7% of cases. These included inactivating mutations in MLL3 (in 14.8% of cases), ROBO2 (9.3%), RNF43 (9.3%) and PEG3 (5.6%), and activating mutations in the GNAS oncogene (9.3%). These genes have functions that can be broadly grouped into three biological classes: (i) deactivation of histone modifiers, (ii) activation of G protein signaling and (iii) loss of genome stability. This study provides insight into the mutational landscape contributing to O. viverrini-related CCA.

Kinetochores and disease: keeping microtubule dynamics in check!

The essential role of microtubules in cell division has long been known. Yet the mechanism by which microtubule attachment to chromosomes at kinetochores is regulated has only been recently revealed. Here, we review the role of kinetochore-microtubule (kMT) attachment dynamics in the cell cycle as well as emerging evidence linking deregulation of kMT attachments to diseases where chromosome mis-segregation and aneuploidy play a central role. Evidence indicates that the dynamic behavior of kMTs must fall within narrow permissible boundaries, which simultaneously allow a level of stability sufficient to establish and maintain chromosome-microtubule attachments and a degree of instability that permits error correction required for accurate chromosome segregation.

Characterization of aneuploid populations with trisomy 7 and 20 derived from diploid human colonic epithelial cells

Chromosomal instability leading to aneuploidy occurs in most sporadic colorectal cancers (CRCs) and is believed to be an early driving force in disease progression. Despite this observation, the cellular advantages conferred by these cytogenetic alterations are poorly understood. Here, we provide evidence that serum-free passage of originally diploid, immortalized human colonic epithelial cells (HCECs) gave rise to the acquisition of trisomy 7 (+7), an aneuploidy detected in more than 40% of colorectal adenomas. These cells remain diploid under long-term growth in 2% serum conditions. Analysis by GTG banding and fluorescent in situ hybridization detected no rare preexisting +7 cell in the original population, suggesting a conversion of diploid cells to an aneuploid state. The acquisition of +7 also precedes loss or truncation of the adenomatosis polyposis coli gene as both diploid and +7 cells express full-length, functional protein. Coculturing of fluorescent-labeled cells demonstrate that +7 HCECs have a growth advantage over diploid cells in serum-free conditions. Defects in cell migration and aberrant regulation of the epidermal growth factor receptor, located on chromosome 7p, are also detected in +7 HCECs. Interestingly, knockdown of TP53 and expression of K-Ras(V12) in +7 HCECs resulted in the emergence of trisomy 20, another nonrandom aneuploidy observed in ∼85% of CRC. In summary, we describe isogenic colonic epithelial cells that represent cytogenetic changes occurring frequently in sporadic CRC. The emergence and characterization of trisomy 7 and 20 demonstrate that these HCECs may serve as unique human cell-based models to examine the effects of chromosomal instability in CRC progression.

A diterpenoid derivative 15-oxospiramilactone inhibits Wnt/β-catenin signaling and colon cancer cell tumorigenesis

The Wnt/β-catenin signaling pathway is a highly conserved pathway in organism evolution and regulates many biological processes. Aberrant activation of the Wnt/β-catenin signaling pathway is closely related to tumorigenesis. In order to identify potent small molecules to treat the over-activated Wnt signaling-mediated cancer, such as colon cancer, we established a mammalian cell line-based reporter gene screening system. The screen revealed a diterpenoid derivative, 15-oxospiramilactone (NC043) that inhibits Wnt3a or LiCl-stimulated Top-flash reporter activity in HEK293T cells and growth of colon cancer cells, SW480 and Caco-2. Treatment of SW480 cells with NC043 led to decreases in the mRNA and/or protein expression of Wnt target genes Axin2, Cyclin D1 and Survivin , as well as decreases in the protein levels of Cdc25c and Cdc2. NC043 did not affect the cytosol-nuclear distribution and protein level of soluble β-catenin, but decreased β-catenin/TCF4 association in SW480 cells. Moreover, NC043 inhibited anchorage-independent growth and xenograft tumorigenesis of SW480 cells. Collectively these results demonstrate that NC043 is a novel small molecule that inhibits canonical Wnt signaling downstream of β-catenin stability and may be a potential compound for treating colorectal cancer.

Mechanisms of chromosomal instability

Most solid tumors are aneuploid, having a chromosome number that is not a multiple of the haploid number, and many frequently mis-segregate whole chromosomes in a phenomenon called chromosomal instability (CIN). CIN positively correlates with poor patient prognosis, indicating that reduced mitotic fidelity contributes to cancer progression by increasing genetic diversity among tumor cells. Here, we review the mechanisms underlying CIN, which include defects in chromosome cohesion, mitotic checkpoint function, centrosome copy number, kinetochore-microtubule attachment dynamics, and cell-cycle regulation. Understanding these mechanisms provides insight into the cellular consequences of CIN and reveals the possibility of exploiting CIN in cancer therapy.

The chromosomal instability pathway in colon cancer

The acquisition of genomic instability is a crucial feature in tumor development and there are at least 3 distinct pathways in colorectal cancer pathogenesis: the chromosomal instability (CIN), microsatellite instability, and CpG island methylator phenotype pathways. Most cases of colorectal cancer arise through the CIN pathway, which is characterized by widespread imbalances in chromosome number (aneuploidy) and loss of heterozygosity. It can result from defects in chromosomal segregation, telomere stability, and the DNA damage response, although the full complement of genes underlying CIN remains incompletely described. Coupled with the karyotypic abnormalities observed in CIN tumors are the accumulation of a characteristic set of mutations in specific tumor suppressor genes and oncogenes that activate pathways critical for colorectal cancer initiation and progression. Whether CIN creates the appropriate milieu for the accumulation of these mutations or vice versa remains a provocative and unanswered question. The goal of this review is to provide an updated perspective on the mechanisms that lead to CIN and the key mutations that are acquired in this pathway.

The chromosomal instability pathway in colon cancer

The acquisition of genomic instability is a crucial feature in tumor development and there are at least 3 distinct pathways in colorectal cancer pathogenesis: the chromosomal instability (CIN), microsatellite instability, and CpG island methylator phenotype pathways. Most cases of colorectal cancer arise through the CIN pathway, which is characterized by widespread imbalances in chromosome number (aneuploidy) and loss of heterozygosity. It can result from defects in chromosomal segregation, telomere stability, and the DNA damage response, although the full complement of genes underlying CIN remains incompletely described. Coupled with the karyotypic abnormalities observed in CIN tumors are the accumulation of a characteristic set of mutations in specific tumor suppressor genes and oncogenes that activate pathways critical for colorectal cancer initiation and progression. Whether CIN creates the appropriate milieu for the accumulation of these mutations or vice versa remains a provocative and unanswered question. The goal of this review is to provide an updated perspective on the mechanisms that lead to CIN and the key mutations that are acquired in this pathway.

Mesalazine inhibits the beta-catenin signalling pathway acting through the upregulation of mu-protocadherin gene in colo-rectal cancer cells

BACKGROUND

Several reports indicate that mesalazine (5-aminosalicylic acid, 5-ASA) is a promising candidate for the chemoprevention of colo-rectal cancer because of its ability to reach the purpose avoiding the unwanted side effects usually associated with prolonged administration of nonsteroidal anti-inflammatory drugs. This activity of 5-ASA is probably the consequence of a number of effects determined on colo-rectal cancer cells, consisting of reduced proliferation, increased apoptosis and activation of cell cycle checkpoints and DNA repair processes. A recent observation has suggested that inhibition of beta-catenin signalling could induce these cellular effects.

AIM

To characterize better the capacity of 5-ASA to inhibit the beta-catenin signalling pathway.

METHODS

Genes belonging to the beta-catenin signalling pathway were analysed in colo-rectal cancer cell lines treated with 5-ASA using a combination of laboratory assays that are able to detect their phenotypic expression and functional activity.

RESULTS

The results obtained indicated that 5-ASA induces the expression of a protein called mu-protocadherin that belongs to the cadherin superfamily and is able to sequester beta-catenin on the plasmatic membrane of treated cells hampering its function.

CONCLUSION

These findings suggest that mu-protocadherin might be employed as a biological marker to monitor the chemopreventive efficacy of 5-ASA.

Cyclin A/cdk2 regulates adenomatous polyposis coli-dependent mitotic spindle anchoring

Mutations in adenomatous polyposis coli (APC) protein is a major contributor to tumor initiation and progression in several tumor types. These mutations affect APC function in the Wnt-beta-catenin signaling and influence mitotic spindle anchoring to the cell cortex and orientation. Here we report that the mitotic anchoring and orientation function of APC is regulated by cyclin A/cdk2. Knockdown of cyclin A and inhibition of cdk2 resulted in cells arrested in mitosis with activation of the spindle assembly checkpoint. The mitotic spindle was unable to form stable attachments to the cell cortex, and this resulted in the spindles failing to locate to the central position in the cells and undergo dramatic rotation. We have demonstrated that cyclin A/cdk2 specifically associates with APC in late G2 phase and phosphorylates it at Ser-1360, located in the mutation cluster region of APC. Mutation of APC Ser-1360 to Ala results in identical off-centered mitotic spindles. Thus, this cyclin A/cdk2-dependent phosphorylation of APC affects astral microtubule attachment to the cortical surface in mitosis.

Beta-catenin expression in uterine sarcomas and its relation to clinicopathological parameters

Aberrations in the Wnt/beta-catenin signalling pathway are suggested as mediators of chromosomal instability and carcinogenesis. beta-catenin acts both as a component of the membranous adhesion system, and as a transcription activator in the nucleus. beta-Catenin immunoreactivity was evaluated in 353 uterine sarcomas (US) including 231 leiomyosarcomas (LMS), 82 endometrial stromal sarcomas (ESS), 22 adenosarcomas (AS) and 18 undifferentiated uterine sarcomas (UUS). Up-regulated membranous beta-catenin was observed in 25% of the LMS (p=0.039), 21% of the ESS (p=0.072) and 39% of the UUS (p=0.025). Cytoplasmic beta-catenin was up-regulated in 36% of the LMS (p=0.008) and 33% of the UUS (p=0.028). Nuclear beta-catenin expression was observed in 23% of the LMS (p=0.051), 61% of ESS (p=0.628) and in the sarcoma component of 68% of the AS. In patients with LMS, membranous beta-catenin was associated with poor crude survival in univariate (p=0.045), but not in multivariate analyses. In patients with ESS, nuclear beta-catenin expression was related to spread of tumour (p=0.033), but not to survival. The observation of up-regulated beta-catenin expression in US might suggest a so far undocumented role for the Wnt/beta-catenin pathway in these malignancies.

Axin localizes to mitotic spindles and centrosomes in mitotic cells

Wnt signaling plays critical roles in cell proliferation and carcinogenesis. In addition, numerous recent studies have shown that various Wnt signaling components are involved in mitosis and chromosomal instability. However, the role of Axin, a negative regulator of Wnt signaling, in mitosis has remained unclear. Using monoclonal antibodies against Axin, we found that Axin localizes to the centrosome and along mitotic spindles. This localization was suppressed by siRNA specific for Aurora A kinase and by Aurora kinase inhibitor. Interestingly, Axin over-expression altered the subcellular distribution of Plk1 and of phosphorylated glycogen synthase kinase (GSK3beta) without producing any notable changes in cellular phenotype. In the presence of Aurora kinase inhibitor, Axin over-expression induced the formation of cleavage furrow-like structures and of prominent astral microtubules lacking midbody formation in a subset of cells. Our results suggest that Axin modulates distribution of Axin-associated proteins such as Plk1 and GSK3beta in an expression level-dependent manner and these interactions affect the mitotic process, including cytokinesis under certain conditions, such as in the presence of Aurora kinase inhibitor.