The genetics of hereditary colon cancer

New Wnt/β-catenin target genes promote experimental metastasis and migration of colorectal cancer cells through different signals

OBJECTIVES

We have previously identified a 115-gene signature that characterises the metastatic potential of human primary colon cancers. The signature included the canonical Wnt target gene BAMBI, which promoted experimental metastasis in mice. Here, we identified three new direct Wnt target genes from the signature, and studied their functions in epithelial-mesenchymal transition (EMT), cell migration and experimental metastasis.

DESIGN

We examined experimental liver metastases following injection of selected tumour cells into spleens of NOD/SCID mice. Molecular and cellular techniques were used to identify direct transcription target genes of Wnt/β-catenin signals. Microarray analyses and experiments that interfered with cell migration through inhibitors were performed to characterise downstream signalling systems.

RESULTS

Three new genes from the colorectal cancer (CRC) metastasis signature, BOP1, CKS2 and NFIL3, were identified as direct transcription targets of β-catenin/TCF4. Overexpression and knocking down of these genes in CRC cells promoted and inhibited, respectively, experimental metastasis in mice, EMT and cell motility in culture. Cell migration was repressed by interfering with distinct signalling systems through inhibitors of PI3K, JNK, p38 mitogen-activated protein kinase and/or mTOR. Gene expression profiling identified a series of migration-promoting genes, which were induced by BOP1, CKS2 and NFIL3, and could be repressed by inhibitors that are specific to these pathways.

CONCLUSIONS

We identified new direct Wnt/β-catenin target genes, BOP1, CKS2 and NFIL3, which induced EMT, cell migration and experimental metastasis of CRC cells. These genes crosstalk with different downstream signalling systems, and activate migration-promoting genes. These pathways and downstream genes may serve as therapeutic targets in the treatment of CRC metastasis.

Comparative effectiveness of chemopreventive interventions for colorectal cancer: protocol for a systematic review and network meta-analysis of randomised controlled trials

BACKGROUND

Colorectal cancer (CRC) is the third most common cancer worldwide and is associated with substantial socioeconomic burden. Despite considerable research, including numerous randomised controlled trials (RCTs) and systematic reviews assessed the effect of various chemopreventive interventions for CRC, there remains uncertainty regarding the comparative effectiveness of these agents. No network meta-analytic study has been published to evaluate the efficacies of these agents for CRC. Therefore, the aim of this study is to summarise the direct and indirect evidence for these interventions to prevent CRC in average-high risk individuals, and to rank these agents for practical consideration.

METHODS

We will acquire eligible studies through a systematic search of MEDLINE, EMBASE, the Cochrane Central Registry of Controlled Trials, CINAHL plus, IPA and clinicaltrials.gov website. The Cochrane Risk of Bias Tool will be used to assess the quality of included studies. The primary outcomes are the incidence of CRC, the incidence/recurrence of any adenoma or change in polyp burden (number or size). Quantitative synthesis or meta-analysis will be considered. We will also construct a network meta-analysis (NMA) to improve precision of the comparisons among chemo-preventive interventions by combining direct and indirect evidence. The probability of each treatment being the best and/or safest, the number-needed-to-treat [NNT; 95% credible interval (CrIs)], and the number-needed-to-harm (NNH; 95% CrIs) will be calculated to provide measures of treatment efficacy. The GRADE approach will be used to rate the quality of evidence of estimates derived from NMA.

RESULTS

This protocol has been registered (registration number: CRD42015025849) with the PROSPERO (International Prospective Register of Systematic Reviews). The procedures of this systematic review and NMA will be conducted in accordance with the PRISMA-compliant guideline. The results of this systematic review and NMA will be submitted to a peer-reviewed journal for publication.

CONCLUSIONS

To the best of our knowledge, this study will be the first NMA to identify the comparative effectiveness of interventions for the prevention of CRC. The results of our study will update evidence for chemoprevention of CRC, identify key areas for future research, and provide a framework for conducting large systematic reviews involving indirect comparisons.

LINE-1 hypomethylation in normal colon mucosa is associated with poor survival in Chinese patients with sporadic colon cancer

Genetic and epigenetic pathways are not independent in colorectal cancer (CRC) carcinogenesis. We aimed to determine the influence of various molecular features on Chinese patients' colon cancer-specific survival (CCSS). Various genetic and epigenetic modifications were detected in paired tumor and normal mucosa tissue samples. The prognostic variables regarding patient CCSS were determined. Overall, 127 patients, including 83 males and 44 females, completed a median follow-up of 65 (3–85) months. A mean LINE-1 methylation rate of 64.62% (range, 9.45–86.93) was observed. Hypermethylation at the hMLH1 gene promoter was detected in 26 (20.47%) patients. KRAS was mutated in 52 (40.94%) patients. Sixteen (12.60%) patients were confirmed as microsatellite instability (MSI)-High, and 76 (59.84%) were found to have loss of heterozygosity at 18q. The LINE-1 methylation level, MSI status, perineural invasion and distant metastases were confirmed as independent prognostic factors for patient CCSS. A stratified survival analysis further revealed that certain subgroups of patients with LINE-1 hypomethylation had significantly worse survival (all p < 0.05). Our data revealed that both genetic and epigenetic abnormalities can concurrently exist during colonic tumorigenesis. As a global epigenetic change, LINE-1 hypomethylation in normal colon mucosa might be associated with a worse outcome in certain Chinese patients with colon cancer.

LKB1 expression reverses the tumorigenicity of L02 cells

The tumor-suppressor liver kinase B1 (LKB1), a highly conserved and ubiquitously expressed protein kinase, plays a critical role in tumorigenesis. In the present study, we revealed that human hepatic L02 cells had severely impaired endogenous LKB1 expression as gauged by western blot, northern blot and RT-PCR analyses. Stable ectopic expression of LKB1 in L02 cells resulted in decreased cell growth, hypophosphorylation of Rb, and marked attenuation of colony formation on soft agar. Inoculation of L02 cells into immunocompromised mice resulted in the development of subcutaneous tumors, which could be completely abrogated by ectopic LKB1 expression. The tumors that formed in the mouse model recapitulated the histopathological features of hepatocellular carcinoma under the microscope. Our results jointly suggest that severely compromised endogenous LKB1 expression in the L02 cell line may confer to L02 cells tumor-initiating capacities in vivo and in vitro, and ectopic LKB1 expression antagonizes the tumorigenic properties of L02 cells. Our findings imply that caution may be needed to interpret the results obtained on the widely used human hepatic L02 cell line. The L02 cell line may be a new model to define the cellular mechanisms of liver transformation, and to unravel the molecular mechanisms underlying the growth suppressive effect of LKB1.

Soy isoflavone consumption and colorectal cancer risk: a systematic review and meta-analysis

Colorectal cancer (CRC) is one of the most predominant solid carcinomas in Western countries. However, there is conflicting information on the effects of soy isoflavone on CRC risk. Therefore, we performed a meta-analysis to assess the association between soy isoflavone consumption and CRC risk in humans using PubMed, Embase, Web of Science, and Cochrane Library databases. A total of 17 epidemiologic studies, which consisted of thirteen case-control and four prospective cohort studies, met the inclusion criteria. Our research findings revealed that soy isoflavone consumption reduced CRC risk (relative risk, RR: 0.78, 95% CI: 0.72-0.85; I(2) = 34.1%, P = 0.024). Based on subgroup analyses, a significant protective effect was observed with soy foods/products (RR: 0.79; 95% CI: 0.69-0.89), in Asian populations (RR: 0.79; 95% CI: 0.72-0.87), and in case-control studies (RR: 0.76; 95% CI: 0.68-0.84). Therefore, soy isoflavone consumption was significantly associated with a reduced risk of CRC risk, particularly with soy foods/products, in Asian populations, and in case-control studies. However, due to the limited number of studies, other factors may affect this association.

Endoscopy-guided orthotopic implantation of colorectal cancer cells results in metastatic colorectal cancer in mice

Advanced stage colorectal cancer (CRC) is still associated with limited prognosis. For preclinical evaluation of novel therapeutic approaches, murine models with orthotopic tumor growth and distant metastases are required. However, these models usually require surgical procedures possibly influencing tumor immunogenicity and development. The aim of this study was to establish a minimal-invasive endoscopy-based murine orthotopic model of metastatic CRC. During colonoscopy of CD-1 nude and non-obese diabetic/severe combined immunodeficiency (NOD/SCID) mice, implantation of Caco-2 and HT-29 CRC cells was performed subcutaneously (s.c.) or orthotopic into the colonic submucosa. White light endoscopy (WLE) and fluorescence endoscopy (FE) were applied for tumor detection in vivo. Ex vivo, resected tumors were examined by fluorescence reflectance imaging (FRI), histology, gelatin zymography and immunohistochemistry. In CD-1 nude mice, marked tumor growth was observed within 14 days after subcutaneous implantation while submucosal implantation failed to induce CRC after 17 weeks. In contrast, in NOD/SCID mice submucosal injection of HT-29 cells resulted in pronounced tumor growth 12 days post injectionem. Subsequently, rapid tumor expansion occurred, occupying the entire colonic circumference. Importantly, post mortem histological analyses confirmed liver metastases in 28.6 % and peritoneal metastases in 14.3 % of all mice. FRI and gelatin zymography did not detect a significantly increased matrix metalloproteinases (MMPs) expression in s.c. implanted tumors while MMP-tracer uptake was significantly enhanced in orthotopic implanted tumors. Neither s.c. nor orthotopic Caco-2 cell implantation resulted in tumor development. We successfully established an endoscopy-based model of metastatic CRC in immunodeficient mice.

Risk of Advanced Neoplasia in First-Degree Relatives with Colorectal Cancer: A Large Multicenter Cross-Sectional Study

BACKGROUND

First-degree relatives (FDR) of patients with colorectal cancer have a higher risk of developing colorectal cancer than the general population. For this reason, screening guidelines recommend colonoscopy every 5 or 10 y, starting at the age of 40, depending on whether colorectal cancer in the index-case is diagnosed at <60 or ≥60 y, respectively. However, studies on the risk of neoplastic lesions are inconclusive. The aim of this study was to determine the risk of advanced neoplasia (three or more non-advanced adenomas, advanced adenoma, or invasive cancer) in FDR of patients with colorectal cancer compared to average-risk individuals (i.e., asymptomatic adults 50 to 69 y of age with no family history of colorectal cancer).

METHODS AND FINDINGS

This cross-sectional analysis includes data from 8,498 individuals undergoing their first lifetime screening colonoscopy between 2006 and 2012 at six Spanish tertiary hospitals. Of these individuals, 3,015 were defined as asymptomatic FDR of patients with colorectal cancer ("familial-risk group") and 3,038 as asymptomatic with average-risk for colorectal cancer ("average-risk group"). The familial-risk group was stratified as one FDR, with one family member diagnosed with colorectal cancer at ≥60 y (n = 1,884) or at <60 y (n = 831), and as two FDR, with two family members diagnosed with colorectal cancer at any age (n = 300). Multiple logistic regression analysis was used for between-group comparisons after adjusting for potential confounders (age, gender, and center). Compared with the average-risk group, advanced neoplasia was significantly more prevalent in individuals having two FDR with colorectal cancer (odds ratio [OR] 1.90; 95% confidence interval [CI] 1.36-2.66, p < 0.001), but not in those having one FDR with colorectal cancer diagnosed at ≥60 y (OR 1.03; 95% CI 0.83-1.27, p = 0.77) and <60 y (OR 1.19; 95% CI 0.90-1.58, p = 0.20). After the age of 50 y, men developed advanced neoplasia over two times more frequently than women and advanced neoplasia appeared at least ten y earlier. Fewer colonoscopies by 2-fold were required to detect one advanced neoplasia in men than in women. Major limitations of this study were first that although average-risk individuals were consecutively included in a randomized control trial, this was not the case for all individuals in the familial-risk cohort; and second, the difference in age between the average-risk and familial-risk cohorts.

CONCLUSIONS

Individuals having two FDR with colorectal cancer showed an increased risk of advanced neoplasia compared to those with average-risk for colorectal cancer. Men had over 2-fold higher risk of advanced neoplasia than women, independent of family history. These data suggest that screening colonoscopy guidelines should be revised in the familial-risk population.

Cutaneous manifestation of gastrointestinal disease

The gastrointestinal (GI) and cutaneous systems are closely linked in origin. Skin manifestations are frequently seen as a part of different GI syndromes. Gastroenterologists play an important role in recognizing the symptoms, patient workup and arriving at appropriate diagnoses, often in consultation with dermatologists. This review discusses the diseases with both cutaneous and intestinal involvement. Hereditary polyposis GI cancers, hereditary nonpolyposis colorectal cancers (CRCs), hamartomatous disorders, and inflammatory bowel disease (IBD) are reviewed with emphasis on the genetic basis, diagnostic, histologic findings, screening modalities, and therapeutic options.

Modeling the Etiology of p53-mutated Cancer Cells

p53 gene mutations are among the most common alterations in cancer. In most cases, missense mutations in one TP53 allele are followed by loss-of-heterozygosity (LOH), so tumors express only mutant p53. TP53 mutations and LOH have been linked, in many cases, with poor therapy response and worse outcome. Despite this, remarkably little is known about how TP53 point mutations are acquired, how LOH occurs, or the cells involved. Nutlin-3a occupies the p53-binding site in MDM2 and blocks p53-MDM2 interaction, resulting in the stabilization and activation of p53 and subsequent growth arrest or apoptosis. We leveraged the powerful growth inhibitory activity of Nutlin-3a to select p53-mutated cells and examined how TP53 mutations arise and how the remaining wild-type allele is lost or inactivated. Mismatch repair (MMR)-deficient colorectal cancer cells formed heterozygote (p53 wild-type/mutant) colonies when cultured in low doses of Nutlin-3a, whereas MMR-corrected counterparts did not. Placing these heterozygotes in higher Nutlin-3a doses selected clones in which the remaining wild-type TP53 was silenced. Our data suggest silencing occurred through a novel mechanism that does not involve DNA methylation, histone methylation, or histone deacetylation. These data indicate MMR deficiency in colorectal cancer can give rise to initiating TP53 mutations and that TP53 silencing occurs via a copy-neutral mechanism. Moreover, the data highlight the use of MDM2 antagonists as tools to study mechanisms of TP53 mutation acquisition and wild-type allele loss or silencing in cells with defined genetic backgrounds.

Tumor and Patient Characteristics of Individuals with Mismatch Repair Deficient Colorectal Cancer

AIMS

To investigate tumor and patient characteristics of individuals with mismatch repair (MMR)-deficient colorectal carcinomas.

METHODS

We immunhistochemically investigated tissue samples of 307 consecutive patients with colorectal cancer for defects in DNA MMR proteins (hMLH1, hMSH2, hMSH6, hPMS2) and those with mutations further for microsatellite instability (MSI) and BRAF V600E mutations.

RESULTS

32/308 (10.4%) tumors showed MMR deficiency. Seventy five percent (n = 24) had loss of hMLH1 and hPMS2 expression, 3% (n = 1) of hPMS2 alone, 18.8% (n = 6) of hMSH6 and hMSH2, 3% (n = 1) of hMSH2 alone. All MMR-deficient tumors showed high MSI. These tumors occurred preferably in the right-sided colon, in women and showed specific histological features. We obtained the family history of 18/32 patients; 2 (11.1%) met Amsterdam Criteria, 5 (27.8%) Bethesda Guidelines and 6 (33.3%) revised Bethesda Guidelines. BRAF V600E mutations were found in 16 (67%) of hMLH1 and none of the hMSH2 deficient tumors.

CONCLUSION

We suggest using immunhistochemical testing of tumor tissues with subsequent MSI analysis, which may be justified as a screening method for MMR deficiency in colorectal cancer, since it identifies patients with possibly hereditary defects and unalike response to chemotherapy.

MicroRNA-224 sustains Wnt/β-catenin signaling and promotes aggressive phenotype of colorectal cancer

BACKGROUND

Growing evidence suggests that Wnt/β-catenin pathway plays an important role in CRC development, progression and metastasis. Aberrant miR-224 expression has been reported in CRC. However, the mechanism of miR-224 promotes both proliferation and metastatic ability largely remains unclear.

METHODS

Real-time PCR was used to quantify miR-224 expression. Luciferase reporter assays were conducted to confirm the activity of Wnt/β-catenin pathway and target gene associations, and immunofluorescence staining assay was performed to observe the nuclear translocation of β-catenin. Bioinformatics analysis combined with in vivo and vitro functional assays showed the potential target genes, GSK3β and SFRP2, of miR-224. Specimens from forty patients with CRC were analyzed for the expression of miR-224 and the relationship with GSK3β/SFRP2 by real-time PCR and western blot.

RESULTS

Bioinformatics and cell luciferase function studies verified the direct regulation of miR-224 on the 3'-UTR of the GSK3β and SFRP2 genes, which leads to the activation of Wnt/β-catenin signaling and the nuclear translocation of β-catenin. In addition, knockdown of miR-224 significantly recovered the expression of GSK3β and SFRP2 and attenuated Wnt/β-catenin-mediated cell metastasis and proliferation. The ectopic upregulation of miR-224 dramatically inhibited the expression of GSK3β/SFRP2 and enhanced CRC proliferation and invasion.

CONCLUSION

Our research showed mechanistic links between miR-224 and Wnt/β-catenin in the pathogenesis of CRC through modulation of GSK3β and SFRP2.

Molecular pathogenesis of sporadic colorectal cancers

Colorectal cancer (CRC) results from the progressive accumulation of genetic and epigenetic alterations that lead to the transformation of normal colonic mucosa to adenocarcinoma. Approximately 75% of CRCs are sporadic and occur in people without genetic predisposition or family history of CRC. During the past two decades, sporadic CRCs were classified into three major groups according to frequently altered/mutated genes. These genes have been identified by linkage analyses of cancer-prone families and by individual mutation analyses of candidate genes selected on the basis of functional data. In the first half of this review, we describe the genetic pathways of sporadic CRCs and their clinicopathologic features. Recently, large-scale genome analyses have detected many infrequently mutated genes as well as a small number of frequently mutated genes. These infrequently mutated genes are likely described in a limited number of pathways. Gene-oriented models of CRC progression are being replaced by pathway-oriented models. In the second half of this review, we summarize the present knowledge of this research field and discuss its prospects.

Mouse models of intestinal cancer

Murine models of intestinal cancer are powerful tools to recapitulate human intestinal cancer, understand its biology and test therapies. With recent developments identifying the importance of the tumour microenvironment and the potential for immunotherapy, autochthonous genetically engineered mouse models (GEMMs) will remain an important part of preclinical studies for the foreseeable future. This review will provide an overview of the current mouse models of intestinal cancer, from the Apc(Min/+) mouse, which has been used for over 25 years, to the latest 'state-of-the-art' organoid models. We discuss here how these models have been used to define fundamental processes involved in tumour initiation and the attempts to generate metastatic models, which is the ultimate cause of cancer mortality. Together these models will provide key insights to understand this complex disease and hopefully will lead to the discovery of new therapeutic strategies.

Copy number variants associated with 18p11.32, DCC and the promoter 1B region of APC in colorectal polyposis patients

Familial Adenomatous Polyposis (FAP) is the second most common inherited predisposition to colorectal cancer (CRC) associated with the development of hundreds to thousands of adenomas in the colon and rectum. Mutations in APC are found in ~ 80% polyposis patients with FAP. In the remaining 20% no genetic diagnosis can be provided suggesting other genes or mechanisms that render APC inactive may be responsible. Copy number variants (CNVs) remain to be investigated in FAP and may account for disease in a proportion of polyposis patients. A cohort of 56 polyposis patients and 40 controls were screened for CNVs using the 2.7M microarray (Affymetrix) with data analysed using ChAS (Affymetrix). A total of 142 CNVs were identified unique to the polyposis cohort suggesting their involvement in CRC risk. We specifically identified CNVs in four unrelated polyposis patients among CRC susceptibility genes APC, DCC, MLH1 and CTNNB1 which are likely to have contributed to disease development in these patients. A recurrent deletion was observed at position 18p11.32 in 9% of the patients screened that was of particular interest. Further investigation is necessary to fully understand the role of these variants in CRC risk given the high prevalence among the patients screened.

CUEDC2 Protects Against Experimental Colitis and Suppresses Excessive Proliferation of Intestinal Mucosa

BACKGROUND

CUEDC2, a CUE domain-containing protein, is highly expressed in many tumors, which also may be associated with inflammation.

AIMS

In this study, we studied whether CUEDC2 plays a role in the progress of inflammatory bowel disease using CUEDC2 knockout (KO) mice and discussed the effects of CUEDC2 on cell proliferation in colonic mucosa.

METHODS

CUEDC2 KO mice were administered with drinking dextran sodium sulfate (DSS) to establish colitis mice model. At different time points after DSS administration, body weight and stool consistency of mice were graded. Cytokines in colon tissue such as IL-6 were measured by RT-PCR. NF-κB and STAT3 signaling pathways in colon tissue were assessed by western blotting. Besides, cell proliferation of intestinal mucosa was analyzed by immunohistochemical staining.

RESULTS

CUEDC2 alleviated the colonic inflammation, showing elevated body weight loss, worse diarrhea, and more severe colonic mucosal injury in CUEDC2 KO mice than WT mice. Moreover, pro-inflammatory cytokines such as IL-6, TNFα, COX2, and MIP2 were significantly elevated. In CUEDC2 KO mice, the NF-κB and STAT3 signaling pathways were increasingly activated in different stages of progression of the colonic inflammation, and the percentage of proliferating cells as indicated by Ki67, CyclinD1, and BrdU in the inflammatory tissues was significantly increased.

CONCLUSIONS

Our findings demonstrate that CUEDC2 plays an important role in protection from colonic inflammation, primarily by inhibiting the NF-κB and STAT3 signaling pathways and preventing excessive proliferation of the inflammatory epithelial cell.

Multistage vector delivery of sulindac and silymarin for prevention of colon cancer

Familial adenomatous polyposis (FAP) is an inherited condition secondary to germline mutations in the APC gene, thus resulting in the formation of hundreds of colonic adenomas that eventually progress into colon cancer. Surgical removal of the colon remains the only treatment option to avoid malignancy, as long-term exposure to chemopreventive agents such as sulindac (a non-steroidal anti-inflammatory drug) and silymarin (phytoestrogen) is not feasible. Here, we have developed a multistage silicon-based drug delivery platform for sulindac and silymarin that preferentially interacts with colon cancer cells as opposed to normal intestinal mucosa. Preferential binding and internalization of these drugs into colon cancer cells was obtained using a targeting strategy against the protein meprin A, which we demonstrate is overexpressed in human colon cancer cells and in the small intestine of Apc(Min/+) mice. We propose that this delivery system could potentially be used to reduce drug-induced side effects in FAP patients, thus enabling long-term prevention of adenoma formation.

Influence of miRNA-106b and miRNA-135a on butyrate-regulated expression of p21 and Cyclin D2 in human colon adenoma cells

Epigenetic and posttranslational modifications of the expression of cell cycle-relevant genes or proteins like p21, e.g., by miRNAs are crucial mechanisms in the development or prevention of colon cancer. The present study investigated the influence of butyrate and trichostatin A (TSA) as histone deacetylase inhibitors on the expression of colon cancer-relevant miRNA (miR-135a, miR-135b, miR-24, miR-106b, miR-let-7a) in LT97 colon adenoma cells as a model of an early stage of colon carcinogenesis. The impact of distinct miRNAs (miR-106b, miR-135a) on butyrate-mediated regulation of p21 and Cyclin D2 gene and protein expression as well as the effect on LT97 cell proliferation (non-transfected, miR-106b and miR-135a mimic transfected) was analyzed. Butyrate and partial TSA reduced the expression of miR-135a, miR-135b, miR-24 and miR-let-7a (~0.5-fold, 24 h) and miR-24, miR-106b and miR-let-7a (~0.5-0.7-fold, 48 h) in LT97 cells. Levels of p21 mRNA and protein were significantly increased by butyrate and TSA (~threefold and 4.5-fold, respectively, 24 h) in non-transfected but not in miR-106b transfected LT97 cells. Levels of Cyclin D2 mRNA were significantly reduced by butyrate and TSA (~0.3-fold, 24 h) in non-transfected and miR-135a-transfected LT97 cells, whereas protein levels were predominantly not influenced. MiR-106b and miR-135a significantly reduced butyrate-/TSA-mediated inhibition of LT97 cell proliferation (72 h). These results indicate that butyrate is able to modify colon cancer-relevant miRNAs like miR-106b and miR-135a which are involved in the regulation of cell cycle-relevant genes like p21 and might influence inhibition of adenoma cell proliferation.

Colorectal cancer screening in the familial risk population: Is colonoscopy still the strategy of choice?

First-degree relatives of patients with colorectal cancer (CRC) are at high risk of this disease. For this reason, medical organizations and clinical guidelines recommend more intensive screening and surveillance for such first-degree relatives than for the average-risk population. Colonoscopy has been the cornerstone of CRC screening in this setting. Although colonoscopy is the most sensitive technique for the detection of neoplastic lesions (especially non-advanced adenomas), its role is less clear for CRC. In addition, screening colonoscopy has several limitations that may affect the success of a screening campaign, such as poor participant acceptance, the need for skilled endoscopists, participant access to screening colonoscopy, overburdened endoscopy units, potential complications, and procedure-related costs. In addition, recent evidence has cast doubt on the advantage of colonoscopy over other strategies for the detection of advanced neoplastic lesions. Despite being less sensitive in general, other screening methods frequently recommended in the average-risk population may be more acceptable and thus help increase CRC screening uptake. This review discusses recent evidence on the risk of CRC in first-degree relatives, the advantages and disadvantages of each screening technique, participation rates depending on the technique, patient preferences, and barriers to screening.

Tissue-Specific Effects of Reduced β-catenin Expression on Adenomatous Polyposis Coli Mutation-Instigated Tumorigenesis in Mouse Colon and Ovarian Epithelium

Adenomatous polyposis coli (APC) inactivating mutations are present in most human colorectal cancers and some other cancers. The APC protein regulates the β-catenin protein pool that functions as a co-activator of T cell factor (TCF)-regulated transcription in Wnt pathway signaling. We studied effects of reduced dosage of the Ctnnb1 gene encoding β-catenin in Apc-mutation-induced colon and ovarian mouse tumorigenesis and cell culture models. Concurrent somatic inactivation of one Ctnnb1 allele, dramatically inhibited Apc mutation-induced colon polyposis and greatly extended Apc-mutant mouse survival. Ctnnb1 hemizygous dose markedly inhibited increases in β-catenin levels in the cytoplasm and nucleus following Apc inactivation in colon epithelium, with attenuated expression of key β-catenin/TCF-regulated target genes, including those encoding the EphB2/B3 receptors, the stem cell marker Lgr5, and Myc, leading to maintenance of crypt compartmentalization and restriction of stem and proliferating cells to the crypt base. A critical threshold for β-catenin levels in TCF-regulated transcription was uncovered for Apc mutation-induced effects in colon epithelium, along with evidence of a feed-forward role for β-catenin in Ctnnb1 gene expression and CTNNB1 transcription. The active β-catenin protein pool was highly sensitive to CTNNB1 transcript levels in colon cancer cells. In mouse ovarian endometrioid adenocarcinomas (OEAs) arising from Apc- and Pten-inactivation, while Ctnnb1 hemizygous dose affected β-catenin levels and some β-catenin/TCF target genes, Myc induction was retained and OEAs arose in a fashion akin to that seen with intact Ctnnb1 gene dose. Our findings indicate Ctnnb1 gene dose exerts tissue-specific differences in Apc mutation-instigated tumorigenesis. Differential expression of selected β-catenin/TCF-regulated genes, such as Myc, likely underlies context-dependent effects of Ctnnb1 gene dosage in tumorigenesis.

Enhanced Wnt signaling contributes to colorectal and other cancers. β-catenin functions in Wnt signaling as a T cell factor (TCF) transcriptional co-activator. Previous studies showed specific β-catenin dosage favors Wnt signaling-dependent tumorigenesis for some tumor types. However, earlier studies emphasized the role of constitutional Ctnnb1 and Apc gene variations, rather than somatic gene targeting, and the work focused on small intestine tumors and no effects on colon tumor phenotypes were described. Furthermore, definitive insights were lacking into how reduced Ctnnb1 gene dosage affected Apc mutation-dependent tumorigenesis. Here, we show somatic inactivation of one Ctnnb1 allele dramatically inhibits mouse colon adenomatous polyposis induced by somatic bi-allelic Apc inactivation. In contrast, Ctnnb1 hemizygous inactivation does not affect mouse ovarian endometrioid adenocarcinoma development arising from Apc- and Pten-inactivation. Ctnnb1 hemizygous gene dose dramatically reduces the active pool of β-catenin, leading to the significant inhibition of β-catenin/TCF-regulated target gene expression, including those encoding key stem cell regulatory and crypt compartmentalization factors in colon epithelium. Tissue-specific differences for expression of selected β-catenin/TCF-regulated genes, such as Myc, may contribute to the context-dependent effects of Ctnnb1 gene dosage in Apc mutation-driven colon and ovarian tumors.

Genetic and epigenetic variants in the MTHFR gene are not associated with non-Hodgkin lymphoma

The methylenetetrahydrofolate reductase (MTHFR) gene codes for the MTHFR enzyme which plays a key role in the pathway of folate and methionine metabolism. Polymorphisms of genes in this pathway affect its regulation and have been linked to lymphoma. In this study we examined whether we could detect an association between two common non-synonymous MTHFR polymorphisms, 677C > T (rs1801133) and 1298A > C (rs1801131), and susceptibility to non-Hodgkin lymphoma (NHL) in an Australian case-control cohort. We found no significant differences between genotype or allele frequencies for either polymorphisms between lymphoma cases and controls. We also explored whether epigenetic modification of MTHFR, specifically DNA methylation of a CpG island in the MTHFR promoter region, is associated with NHL using blood samples from patients. No difference in methylation levels was detected between the case and control samples suggesting that although hypermethylation of MTHFR has been reported in tumour tissues, particularly in the diffuse large B-cell lymphoma subtype of NHL, methylation of this MTHFR promoter CpG island is not a suitable epigenetic biomarker for NHL diagnosis or prognosis in peripheral blood samples. Further studies into epigenetic variants could focus on genes that are robustly associated with NHL susceptibility.

5-Fluorouracil mediated anti-cancer activity in colon cancer cells is through the induction of Adenomatous Polyposis Coli: Implication of the long-patch base excision repair pathway

Colorectal cancer (CRC) patients with APC mutations do not benefit from 5-FU therapy. It was reported that APC physically interacts with POLβ and FEN1, thus blocking LP-BER via APC's DNA repair inhibitory (DRI) domain in vitro. The aim of this study was to elucidate how APC status affects BER and the response of CRC to 5-FU. HCT-116, HT-29, and LOVO cells varying in APC status were treated with 5-FU to evaluate expression, repair, and survival responses. HCT-116 expresses wild-type APC; HT-29 expresses an APC mutant that contains DRI domain; LOVO expresses an APC mutant lacking DRI domain. 5-FU increased the expression of APC and decreased the expression of FEN1 in HCT-116 and HT-29 cells, which were sensitized to 5-FU when compared to LOVO cells. Knockdown of APC in HCT-116 rendered cells resistant to 5-FU, and FEN1 levels remained unchanged. Re-expression of full-length APC in LOVO cells caused sensitivity to 5-FU, and decreased expression of FEN1. These knockdown and addback studies confirmed that the DRI domain is necessary for the APC-mediated reduction in LP-BER and 5-FU. Modelling studies showed that 5-FU can interact with the DRI domain of APC via hydrogen bonding and hydrophobic interactions. 5-FU resistance in CRC occurs with mutations in APC that disrupt or eliminate the DRI domain's interaction with LP-BER. Understanding the type of APC mutation should better predict 5-FU resistance in CRC than simply characterizing APC status as wild-type or mutant.

Value of screening endoscopy in evaluation of esophageal, gastric and colon cancers

Esophageal, gastric, and colorectal cancers are deadly diseases that continue to plague our world today. The value of screening endoscopy in evaluating these types of cancers is a critical area of discussion due to a potential reduction in morbidity and mortality. This article describes how to identify a good screening test and explains what are important criteria in the field of screening endoscopy. Furthermore, the current status and progress of screening endoscopy for esophageal, gastric, and colorectal cancer will be evaluated and discussed. Mass screening programs have not been implemented for esophageal and gastric carcinomas in those with average or low risk populations. However, studies of high-risk populations have found value and a cost-benefit in conducting screening endoscopy. Colorectal cancer, on the other hand, has had mass screening programs in place for many years due to the clear evidence of improved outcomes. As the role of endoscopy as a screening tool has continued to develop, newer technology and techniques have emerged to improve its utility. Many new image enhancement techniques and computer processing programs have shown promise and may have a significant role in the future of endoscopic screening. These developments are paving the way for improving the diagnostic and therapeutic capability of endoscopy in the field of gastroenterology.

Women with double primary cancers of the colorectum and endometrium: do they have Lynch syndrome?

OBJECTIVE

The aim of this study was to determine the clinical characteristics of women with double primary cancers of the colorectum and endometrium and assess the probability of Lynch syndrome.

STUDY DESIGN

We identified 15 women with paraffin-embedded blocks available who were diagnosed, treated and followed for double primary colorectal and endometrial cancers at in a single institution between 1994 and 2014. If there was a family history that met the revised Amsterdam criteria for Lynch syndrome, the woman was considered to have 'clinically defined Lynch syndrome'. If immunohistochemical (IHC) loss of expression of mismatch repair genes (MLH1, MSH2, MSH6, or PMS2) or high microsatellite instability (MSI) was demonstrated in molecular testing, the case was considered 'suspected Lynch syndrome'.

RESULTS

The incidence of clinically defined Lynch syndrome according to the revised Amsterdam criteria was 66% (8 of 15). All 8 of the women clinically diagnosed with Lynch syndrome had either abnormal IHC loss or MSI-high, indicating a suspected Lynch syndrome. Furthermore, 27% (4 of 15) experienced second primary colorectal cancer or other Lynch syndrome-related cancers. Overall, 66% (10 of 15) met the criteria for clinically defined Lynch syndrome or suspected Lynch syndrome.

CONCLUSIONS

Based on our findings, a large percentage (66%) of women with double primary cancers of the colorectum and endometrium are likely to be diagnosed with Lynch syndrome.

DCLK1 facilitates intestinal tumor growth via enhancing pluripotency and epithelial mesenchymal transition

Doublecortin-like kinase 1 (Dclk1) is overexpressed in many cancers including colorectal cancer (CRC) and it specifically marks intestinal tumor stem cells. However, the role of Dclk1 in intestinal tumorigenesis in Apc mutant conditions is still poorly understood. We demonstrate that Dclk1 expression and Dclk1+ cells are significantly increased in the intestinal epithelium of elderly Apc^Min/+ mice compared to young Apc^Min/+ mice and wild type mice. Intestinal epithelial cells of Apc^Min/+ mice demonstrate increased pluripotency, self-renewing ability, and EMT. Furthermore, miRNAs are dysregulated, expression of onco-miRNAs are significantly increased with decreased tumor suppressor miRNAs. In support of these findings, knockdown of Dclk1 in elderly Apc^Min/+ mice attenuates intestinal adenomas and adenocarcinoma by decreasing pluripotency, EMT and onco-miRNAs indicating that Dclk1 overexpression facilitates intestinal tumorigenesis. Knocking down Dclk1 weakens Dclk1-dependent intestinal processes for tumorigenesis. This study demonstrates that Dclk1 is critically involved in facilitating intestinal tumorigenesis by enhancing pluripotency and EMT factors in Apc mutant intestinal tumors and it also provides a potential therapeutic target for the treatment of colorectal cancer.

The chemopreventive potential of Curcuma purpurascens rhizome in reducing azoxymethane-induced aberrant crypt foci in rats

Curcuma purpurascens BI. rhizome, a member of the Zingiberaceae family, is a popular spice in Indonesia that is traditionally used in assorted remedies. Dichloromethane extract of C. purpurascens BI. rhizome (DECPR) has previously been shown to have an apoptosis-inducing effect on colon cancer cells. In the present study, we examined the potential of DECPR to prevent colon cancer development in rats treated with azoxymethane (AOM) (15 mg/kg) by determining the percentage inhibition in incidence of aberrant crypt foci (ACF). Starting from the day immediately after AOM treatment, three groups of rats were orally administered once a day for 2 months either 10% Tween 20 (5 mL/kg, cancer control), DECPR (250 mg/kg, low dose), or DECPR (500 mg/kg, high dose). Meanwhile, the control group was intraperitoneally injected with 5-fluorouracil (35 mg/kg) for 5 consecutive days. After euthanizing the rats, the number of ACF was enumerated in colon tissues. Bax, Bcl-2, and proliferating cell nuclear antigen (PCNA) protein expressions were examined using immunohistochemical and Western blot analyses. Antioxidant enzymatic activity was measured in colon tissue homogenates and associated with malondialdehyde level. The percentage inhibition of ACF was 56.04% and 68.68% in the low- and high-dose DECPR-treated groups, respectively. The ACF inhibition in the treatment control group was 74.17%. Results revealed that DECPR exposure at both doses significantly decreased AOM-induced ACF formation, which was accompanied by reduced expression of PCNA. Upregulation of Bax and downregulation of Bcl-2 suggested the involvement of apoptosis in the chemopreventive effect of DECPR. In addition, the oxidative stress resulting from AOM treatment was significantly attenuated after administration of DECPR, which was shown by the elevated antioxidant enzymatic activity and reduced malondialdehyde level. Taken together, the present data clearly indicate that DECPR significantly inhibits ACF formation in AOM-treated rats and may offer protection against colon cancer development.

Multiple Gastrointestinal Polyps in Patients Treated with BRAF Inhibitors

PURPOSE

BRAF inhibitors (BRAFi) extend survival in BRAF-mutant melanoma but can promote the growth of Ras-mutant neoplasms. This study determined if gastrointestinal polyps found in BRAFi-treated patients harbored Ras mutations.

EXPERIMENTAL DESIGN

Colonic and gastric polyps were identified and resected from BRAFi-treated melanoma patients. Next-generation sequencing (NGS) was performed on polyps. The ability of BRAFi to promote polyp formation was functionally characterized in Apc Min(+/-) mice. MAPK and β-catenin pathway activity was assessed by immunohistochemistry in mouse and human polyps.

RESULTS

Fourteen patients treated with BRAFi underwent endoscopy to assess for polyps. Seven out of 7 patients >40 years of age and treated for >2 years were found to have colonic tubular adenomas with 4 out of the 7 patients having 5 or more polyps. One patient presented with bleeding from hyperplastic gastric polyps that recurred 6 months after BRAFi rechallenge. NGS performed on polyps found no mutations in MAPK pathway genes, but found APC mutations in all tubular adenomas. A significant increase in the number of polyps was observed in BRAFi-treated compared with control-treated Apc Min(+/-) mice (20.8 ± 9.2 vs 12.8 ± 0.1; P = 0.016). No polyps were observed in BRAFi-treated wild-type mice.

CONCLUSIONS

BRAFi may increase the risk of developing hyperplastic gastric polyps and colonic adenomatous polyps. Due to the risk of gastrointestinal bleeding and the possibility of malignant transformation, further studies are needed to determine whether or not endoscopic surveillance should be recommended for patients treated with BRAFi.

Genetics, diagnosis and management of colorectal cancer (Review)

Colorectal cancer (CRC) is the third most common type of cancer worldwide and a leading cause of cancer death. Surgery represents the mainstay of treatment in early cases but often patients are primarily diagnosed in an advanced stage of disease and sometimes also distant metastases are present. Neoadjuvant therapy is therefore needed but drug resistance may influence response and concur to recurrent disease. At molecular level, it is a very heterogeneous group of diseases with about 30% of hereditary or familial cases. During colorectal adenocarcinomas development, epithelial cells from gastrointestinal trait acquire sequential genetic and epigenetic mutations in specific oncogenes and/or tumour suppressor genes, causing CRC onset, progression and metastasis. Molecular characterization of cancer associated mutations gives valuable information about disease prognosis and response to the therapy. Very early diagnosis and personalized care, as well as a better knowledge of molecular basis of its onset and progression, are therefore crucial to obtain a cure of CRC. In this review, we describe updated genetics, current diagnosis and management of CRC pointing out the extreme need for a multidisciplinary approach to achieve the best results in patient outcomes.

Genetic mutations in human rectal cancers detected by targeted sequencing

Colorectal cancer (CRC) is widespread with significant mortality. Both inherited and sporadic mutations in various signaling pathways influence the development and progression of the cancer. Identifying genetic mutations in CRC is important for optimal patient treatment and many approaches currently exist to uncover these mutations, including next-generation sequencing (NGS) and commercially available kits. In the present study, we used a semiconductor-based targeted DNA-sequencing approach to sequence and identify genetic mutations in 91 human rectal cancer samples. Analysis revealed frequent mutations in KRAS (58.2%), TP53 (28.6%), APC (16.5%), FBXW7 (9.9%) and PIK3CA (9.9%), and additional mutations in BRAF, CTNNB1, ERBB2 and SMAD4 were also detected at lesser frequencies. Thirty-eight samples (41.8%) also contained two or more mutations, with common combination mutations occurring between KRAS and TP53 (42.1%), and KRAS and APC (31.6%). DNA sequencing for individual cancers is of clinical importance for targeted drug therapy and the advantages of such targeted gene sequencing over other NGS platforms or commercially available kits in sensitivity, cost and time effectiveness may aid clinicians in treating CRC patients in the near future.

Pancreatic cancer: current understanding of molecular and genetic aetiologies

Pancreatic ductal adenocarcinoma (PDAC) is one of the few cancers where prognosis has not improved over the past few decades. However, there have been several advances in our understanding of the disease leading to earlier detection and targeted therapeutic treatment. It is now understood that specific somatic and germline mutations lead to the development of the disease, and the risk factors associated with this are clearer. Further, several precursor lesions have been identified which, with early detection and surveillance, allows treatment before the development of carcinoma. PDAC can now be diagnosed with a high sensitivity and specificity following advances in radiology, and treatment can be commenced at an earlier stage of the disease. With continued research we are hopeful that the next decade will see an improved survival rate for all patients with pancreatic cancer.

Netrin-1 as a potential target for metastatic cancer: focus on colorectal cancer

Despite advanced screening technology and cancer treatments available today, metastasis remains an ongoing major cause of cancer-related deaths worldwide. Typically, colorectal cancer is one of the cancers treatable by surgery in conjunction with chemotherapy when it is detected at an early stage. However, it still ranks as the second highest modality and mortality of cancer types in western countries, and this is mostly due to a recurrence of metastatic colorectal cancer post-resection of the primary malignancy. Colorectal cancer metastases predominantly occur in the liver and lung, and yet the molecular mechanisms that regulate these organ-specific colorectal cancer metastases are largely unknown. Therefore, the identification of any critical molecule, which triggers malignancy in colorectal cancer, would be an excellent target for treatment. Netrin-1 was initially discovered as a chemotropic neuronal guidance molecule, and has been marked as a regulator for many cancers including colorectal cancer. Here, we summarise key findings of the role of netrin-1 intrinsic to colorectal cancer cells, extrinsic to the tumour microenvironment and angiogenesis, and consequently, we evaluate netrin-1 as a potential target molecule for metastasis.

Validation of Prediction Models for Mismatch Repair Gene Mutations in Koreans

PURPOSE

Lynch syndrome, the commonest hereditary colorectal cancer syndrome, is caused by germline mutations in mismatch repair (MMR) genes. Three recently developed prediction models for MMR gene mutations based on family history and clinical features (MMRPredict, PREMM(1,2,6), and MMRPro) have been validated only in Western countries. In this study, we propose validating these prediction models in the Korean population.

MATERIALS AND METHODS

We collected MMR gene analysis data from 188 individuals in the Korean Hereditary Tumor Registry. The probability of gene mutation was calculated using three prediction models, and the overall diagnostic value of each model compared using receiver operator characteristic (ROC) curves and area under the ROC curve (AUC). Quantitative test characteristics were calculated at sensitivities of 90%, 95%, and 98%.

RESULTS

Of the individuals analyzed, 101 satisfied Amsterdam criteria II, and 87 were suspected hereditary nonpolyposis colorectal cancer. MMR mutations were identified in 62 of the 188 subjects (33.0%). All three prediction models showed a poor predictive value of AUC (MMRPredict, 0.683; PREMM(1,2,6), 0.709; MMRPro, 0.590). Within the range of acceptable sensitivity (> 90%), PREMM(1,2,6) demonstrated higher specificity than the other models.

CONCLUSION

In the Korean population, overall predictive values of the three models (MMRPredict, PREMM(1,2,6), MMRPro) for MMR gene mutations are poor, compared with their performance in Western populations. A new prediction model is therefore required for the Korean population to detect MMR mutation carriers, reflecting ethnic differences in genotype-phenotype associations.

Genome-wide linkage analysis and tumoral characterization reveal heterogeneity in familial colorectal cancer type X

BACKGROUND

Familial colorectal cancer type X (FCCTX) fulfils clinical criteria defining Lynch syndrome (LS), but is not related to germline mutations in DNA mismatch-repair genes. Its aetiology remains unexplained and there is little evidence of involvement of the common colorectal carcinogenetic pathways. We aimed to identify susceptibility loci and gain insights into carcinogenic pathways involved FCCTX tumour development.

METHODS

We performed a linkage analysis in 22 FCCTX families. We also constructed a tissue microarray in order to define an immunohistochemical (IHC) profile for FCCTX tumours (N = 27) by comparing them to three other types of colorectal tumors: LS (N = 18), stable early-onset (N = 31) and other sporadic disease (N = 80). Additionally, we screened for BRAF/KRAS mutations and determined CpG island methylator phenotype (CIMP) status for all FCCTX tumours.

RESULTS

We found suggestive evidence of linkage at four chromosomal regions; 2p24.3, 4q13.1, 4q31.21 and 12q21.2-q21.31. We screened genes in 12q21 and ruled out the implication of RASSF9 and NTS, good candidates due to their potential involvement in carcinogenesis and colorectal epithelium development. Based on IHC profiles FCCTX tumours did not form a single, exclusive cluster. They were clearly different from LS, but very similar to stable early onset tumours. The CIMP and chromosomal instability pathways were implicated in one-third and one-quarter of FCCTX cases, respectively. The remaining cases did not have alterations in any known carcinogenic pathways.

CONCLUSIONS

Our results highlight the heterogeneity of FCCTX tumours and call into question the utility of using only clinical criteria to identify FCCTX cases.

Tumor-Elicited Inflammation and Colorectal Cancer

The link between chronic inflammation and cancer has long been suspected, due to the pioneering work of Rudolf Virchow over 150 years ago. Yet the causal relationship between inflammation and cancer was only deciphered in the past decade or so, using animal models of various cancers. Up to 20% of all human cancers result from chronic inflammation and persistent infections. Proinflammatory cytokines and tumor-infiltrating myeloid and immune cells play critical roles in almost every developmental stages of inflammation-induced cancers, from initiation, promotion, and progression to malignant metastasis. However, even in cancers with no preceding inflammation, inflammatory cells infiltrate tumor stroma and contribute to cancer development. Such "tumor-elicited inflammation" further emphasizes the importance of inflammation in different types of cancers, including that of the colon. In this review, we summarize our current knowledge of the function and induction mechanisms of inflammatory cytokines during colorectal cancer development, and hope to provide insight into the development of novel anticancer therapies by modulating tumor-elicited inflammation.

Prevalence of MLH1 constitutional epimutations as a cause of Lynch syndrome in unselected versus selected consecutive series of patients with colorectal cancer

BACKGROUND

The prevalence of MLH1 constitutional epimutations in the general population is unknown. We sought to analyse the prevalence of MLH1 constitutional epimutations in unselected and selected series of patients with colorectal cancer (CRC).

METHODS

Patients with diagnoses of CRC (n=2123) were included in the unselected group. For comparison, a group of 847 selected patients with CRC who fulfilled the revised Bethesda guidelines (rBG) were also included. Somatic and constitutional MLH1 methylation was assayed via methylation-specific multiplex ligation-dependent probe amplification of cases lacking MLH1 expression. Germline alterations in mismatch-repair (MMR) genes were assessed via Sanger sequencing and methylation-specific multiplex ligation-dependent probe amplification.

RESULTS

Loss of MLH1 expression occurred in 5.5% of the unselected series and 12.5% of the selected series (p<0.0001). No constitutional epimutations in MLH1 were detected in the unselected population (0/62); five cases from the selected series were positive for MLH1 epimutations (15.6%, 5/32; p=0.004).

CONCLUSIONS

Our results suggest a negligible prevalence of MLH1 constitutional epimutations in unselected cases of CRC. Therefore, MLH1 constitutional epimutation analysis should be conducted only for patients who fulfil the rBG and who lack MLH1 expression with methylated MLH1.

The calcium-sensing receptor suppresses epithelial-to-mesenchymal transition and stem cell- like phenotype in the colon

BACKGROUND

The calcium sensing receptor (CaSR), a calcium-binding G protein-coupled receptor is expressed also in tissues not directly involved in calcium homeostasis like the colon. We have previously reported that CaSR expression is down-regulated in colorectal cancer (CRC) and that loss of CaSR provides growth advantage to transformed cells. However, detailed mechanisms underlying these processes are largely unknown.

METHODS AND RESULTS

In a cohort of 111 CRC patients, we found significant inverse correlation between CaSR expression and markers of epithelial-to-mesenchymal transition (EMT), a process involved in tumor development in CRC. The colon of CaSR/PTH double-knockout, as well as the intestine-specific CaSR knockout mice showed significantly increased expression of markers involved in the EMT process. In vitro, stable expression of the CaSR (HT29(CaSR)) gave a more epithelial-like morphology to HT29 colon cancer cells with increased levels of E-Cadherin compared with control cells (HT29(EMP)). The HT29(CaSR) cells had reduced invasive potential, which was attributed to the inhibition of the Wnt/β-catenin pathway as measured by a decrease in nuclear translocation of β-catenin and transcriptional regulation of genes like GSK-3β and Cyclin D1. Expression of a spectrum of different mesenchymal markers was significantly down-regulated in HT29(CaSR) cells. The CaSR was able to block upregulation of mesenchymal markers even in an EMT-inducing environment. Moreover, overexpression of the CaSR led to down-regulation of stem cell-like phenotype.

CONCLUSIONS

The results from this study demonstrate that the CaSR inhibits epithelial-to-mesenchymal transition and the acquisition of a stem cell-like phenotype in the colon of mice lacking the CaSR as well as colorectal cancer cells, identifying the CaSR as a key molecule in preventing tumor progression. Our results support the rationale to develop new strategies either preventing CaSR loss or reversing its silencing.

Epsin is required for Dishevelled stability and Wnt signalling activation in colon cancer development

Uncontrolled canonical Wnt signalling supports colon epithelial tumour expansion and malignant transformation. Understanding the regulatory mechanisms involved is crucial for elucidating the pathogenesis of and will provide new therapeutic targets for colon cancer. Epsins are ubiquitin-binding adaptor proteins upregulated in several human cancers; however, the involvement of epsins in colon cancer is unknown. Here we show that loss of intestinal epithelial epsins protects against colon cancer by significantly reducing the stability of the crucial Wnt signalling effector, dishevelled (Dvl2), and impairing Wnt signalling. Consistently, epsins and Dvl2 are correspondingly upregulated in colon cancer. Mechanistically, epsin binds Dvl2 via its epsin N-terminal homology domain and ubiquitin-interacting motifs and prohibits Dvl2 polyubiquitination and degradation. Our findings reveal an unconventional role for epsins in stabilizing Dvl2 and potentiating Wnt signalling in colon cancer cells to ensure robust colon cancer progression. The pro-carcinogenic role of Epsins suggests that they are potential therapeutic targets to combat colon cancer.

Non-invasive assessment of the efficacy of new therapeutics for intestinal pathologies using serial endoscopic imaging of live mice

Animal models of inflammatory bowel disease (IBD) and colorectal cancer (CRC) have provided significant insight into the cell intrinsic and extrinsic mechanisms that contribute to the onset and progression of intestinal diseases. The identification of new molecules that promote these pathologies has led to a flurry of activity focused on the development of potential new therapies to inhibit their function. As a result, various pre-clinical mouse models with an intact immune system and stromal microenvironment are now heavily used. Here we describe three experimental protocols to test the efficacy of new therapeutics in pre-clinical models of (1) acute mucosal damage, (2) chronic colitis and/or colitis-associated colon cancer, and (3) sporadic colorectal cancer. We also outline procedures for serial endoscopic examination that can be used to document the therapeutic response of an individual tumor and to monitor the health of individual mice. These protocols provide complementary experimental platforms to test the effectiveness of therapeutic compounds shown to be well tolerated by mice.

Hereditary and common familial colorectal cancer: evidence for colorectal screening

Colorectal cancer (CRC) is the fourth most common cancer among men and women. Between 3 and 6% of all CRCs are attributed to well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis, MUTYH-associated polyposis and several hamartomatous conditions. Up to 30% of CRC cases exhibit common familial risk, likely related to a combination of inherited factors and environment. Identification of these patients through family history and appropriate genetic testing can provide estimates of cancer risk that inform appropriate cancer screening, surveillance and/or preventative interventions. This article examines the colon cancer syndromes, their genetic basis, clinical management and evidence supporting colorectal screening. It also deals with the category of common (non-syndromic) familial risk including risk determination and screening guidelines.

Association between appendectomy and subsequent colorectal cancer development: an Asian population study

Objectives

The appendix may modulate colon microbiota and bowel inflammation. We investigated whether appendectomy alters colorectal cancer risk.

Methods

We identified a cohort of 75979 patients who underwent appendectomy between 1997 and 1999 based on the insurance claims of Taiwan. A comparison cohort of 303640 persons without appendectomy was selected randomly, frequency matched by age, sex, comorbidity and entry year was also selected. We monitored subsequent colorectal cancer development in both cohorts.

Results

The overall colorectal cancer incidence was 14% higher in the appendectomy patients than in the comparison cohort (p <0.05): the highest incidence was observed for rectal cancer, and the lowest incidence was observed for cancer of the cecum-ascending colon for both cohorts. Men were at higher risk than women. Subjects ≥ 60 years had an HR of 12.8 compared to those <60 years. The incidence of colorectal cancer was much higher in 1.5-3.5 years post appendectomy follow-up than for the comparisons (HR of 2.13). Patients who received an incidental appendectomy had an HR of 2.90 when compared to the comparisons.

Conclusions

Results of our study suggest that appendectomy in patients with appendicitis is likely associated with the development of colorectal cancer in the post-surgery period.

The Emerging Genetic Basis and Its Clinical Implication in Pancreatic Cancer

<b><i>Background:</i></b> Pancreatic cancer is one of the most devastating diseases without early detection, effective screening biomarkers and therapeutic treatments. In the past decades, genetic studies have indicated various genes related to this malignancy. <b><i>Summary:</i></b> Genetic alterations have been involved in the initiation, progression and invasion of pancreatic cancer, which might indicate promising targets for early screening, diagnosis and future intervention. Here we will review genetic changes in pancreatic cancer and analyze their correlations with several common precursors and familial syndromes. <b><i>Key Message:</i></b> Genetic analysis for pancreatic cancer or its precursors might help us to characterize patients into subtype individuals in the future and have significant implications for individualized treatments. <b><i>Practical Implications:</i></b> At present, pancreatic cancer is regarded as a disease with a wide range of genetic alterations, including germline and somatic mutations. Some genetic alterations such as <i>KRAS</i>, <i>p16</i>^{<i>CDKN2A</i>}, <i>TP53</i> and <i>SMAD4</i> were specifically correlated with different types of histological precursors of pancreatic cancer and some familial syndromes highly related to pancreatic cancer. Moreover, genetic changes also predict drug sensitivity and implicate novel therapeutic targets.

Emerging importance of mismatch repair components including UvrD helicase and their cross-talk with the development of drug resistance in malaria parasite

Human malaria is an important parasitic infection responsible for a significant number of deaths worldwide, particularly in tropical and subtropical regions. The recent scenario has worsened mainly because of the emergence of drug-resistant malaria parasites having the potential to spread across the world. Drug-resistant parasites possess a defective mismatch repair (MMR); therefore, it is essential to explore its mechanism in detail to determine the underlying cause. Recently, artemisinin-resistant parasites have been reported to exhibit nonsynonymous single nucleotide polymorphisms in genes involved in MMR pathways such as MutL homolog (MLH) and UvrD. Plasmodium falciparum MLH is an endonuclease required to restore the defective MMR in drug-resistant W2 strain of P. falciparum. Although the role of helicases in eukaryotic MMR has been questioned, the identification and characterization of the UvrD helicase and their cross-talk with MLH in P. falciparum suggests the possible involvement of UvrD in MMR. A comparative genome-wide analysis revealed the presence of the UvrD helicase in Plasmodium species, while it is absent in human host. Therefore, PfUvrD may emerge as a suitable drug target to control malaria. This review study is focused on recent developments in MMR biochemistry, emerging importance of the UvrD helicase, possibility of its involvement in MMR and the emerging cross-talk between MMR components and drug resistance in malaria parasite.

Causes and consequences of microsatellite instability in gastric carcinogenesis

Loss of DNA mismatch repair (MMR) function, due to somatic or germline epi/genetic alterations of MMR genes leads to the accumulation of numerous mutations across the genome, creating a molecular phenotype known as microsatellite instability (MSI). In gastric cancer (GC), MSI occurs in about 15% to 30% of the cases. This review summarizes the current knowledge on the molecular mechanisms underlying the acquisition of MSI in GC as well as on the clinic, pathologic and molecular consequences of the MSI phenotype. Additionally, current therapeutic strategies for GC and their applicability in the MSI subset are also discussed.

Portrait of the PI3K/AKT pathway in colorectal cancer

PI3K/AKT signaling leads to reduced apoptosis, stimulates cell growth and increases proliferation. Under normal conditions, PI3K/AKT activation is tightly controlled and dependent on both extracellular growth signals and the availability of amino acids and glucose. Genetic aberrations leading to PI3K/AKT hyper-activation are observed at considerable frequency in all major nodes in most tumors. In colorectal cancer the most commonly observed pathway changes are IGF2 overexpression, PIK3CA mutations and PTEN mutations and deletions. Combined, these alterations are found in about 40% of large bowel tumors. In addition, but not mutually exclusive to these, KRAS mutations are observed at a similar frequency. There are however additional, less frequent and more poorly understood events that may also push the PI3K/AKT pathway into overdrive and thus promote malignant growth. Here we discuss aberrations of components at the genetic, epigenetic, transcriptional, post-transcriptional, translational and post-translational level where perturbations may drive excessive PI3K/AKT signaling. Integrating multiple molecular levels will advance our understanding of this cancer critical circuit and more importantly, improve our ability to pharmacologically target the pathway in view of clonal development, tumor heterogeneity and drug resistance mechanisms. In this review, we revisit the PI3K/AKT pathway cancer susceptibility syndromes, summarize the known aberrations at the different regulatory levels and the prognostic and predictive values of these alterations in colorectal cancer.

β1 integrin mediates colorectal cancer cell proliferation and migration through regulation of the Hedgehog pathway

β1 integrin (ITGB1) is the major expressed integrin protein of normal cells and tumor-associated cells. It is often up-regulated in human malignancies and is involved in many developmental processes, such as tumor progression and metastasis. However, little is known about the function of ITGB1 in colorectal cancer. We constructed lentiviral vectors expressing ITGB1 or ITGB1-specific RNA interference (RNAi) and an unrelated control vector. After infecting HT29 cells in vitro, proliferation and migration were evaluated by Cell Counting Kit 8 (CCK-8) assays, transwell invasion assays, and Western blots. The influence of lentivirus infection on the tumor development capacity of HT29 cells in vivo was examined by xenografting the tumor cells. The expression of ITGB1 in the xenografted tumor cells was analyzed by immunohistochemistry. The up-regulation of ITGB1 significantly increased the proliferation in HT29 cells in vitro. Moreover, we found that the overexpression of ITGB1 up-regulated sonic hedgehog (Shh) while down-regulating Gli1 and SuFu in HT29-ITGB1 cells compared to controls. Moreover, the levels of c-myc and cyclin D1 proteins were up-regulated. Transwell assays showed that the number of migrating HT29-RNAi cells was lower than that in the other cell groups, indicating that ITGB1 significantly enhances the invasive ability of HT29 cells. In addition to these in vitro results, ITGB1 was found to be a significantly effective growth factor in a xenografted tumor mouse model. These results suggest that ITGB1 induces growth and invasion in a human colorectal cancer cell line through the hedgehog (Hh) signaling pathway in vitro and in vivo.

MRE11-deficiency associated with improved long-term disease free survival and overall survival in a subset of stage III colon cancer patients in randomized CALGB 89803 trial

Purpose

Colon cancers deficient in mismatch repair (MMR) may exhibit diminished expression of the DNA repair gene, MRE11, as a consequence of contraction of a T₁₁ mononucleotide tract. This study investigated MRE11 status and its association with prognosis, survival and drug response in patients with stage III colon cancer.

Patients and Methods

Cancer and Leukemia Group B 89803 (Alliance) randomly assigned 1,264 patients with stage III colon cancer to postoperative weekly adjuvant bolus 5-fluorouracil/leucovorin (FU/LV) or irinotecan+FU/LV (IFL), with 8 year follow-up. Tumors from these patients were analyzed to determine stability of a T₁₁ tract in the MRE11 gene. The primary endpoint was overall survival (OS), and a secondary endpoint was disease-free survival (DFS). Non-proportional hazards were addressed using time-dependent covariates in Cox analyses.

Results

Of 625 tumor cases examined, 70 (11.2%) exhibited contraction at the T₁₁ tract in one or both MRE11 alleles and were thus predicted to be deficient in MRE11 (dMRE11). In pooled treatment analyses, dMRE11 patients showed initially reduced DFS and OS but improved long-term DFS and OS compared with patients with an intact MRE11 T₁₁ tract. In the subgroup of dMRE11 patients treated with IFL, an unexplained early increase in mortality but better long-term DFS than IFL-treated pMRE11 patients was observed.

Conclusions

Analysis of this relatively small number of patients and events showed that the dMRE11 marker predicts better prognosis independent of treatment in the long-term. In subgroup analyses, dMRE11 patients treated with irinotecan exhibited unexplained short-term mortality. MRE11 status is readily assayed and may therefore prove to be a useful prognostic marker, provided that the results reported here for a relatively small number of patients can be generalized in independent analyses of larger numbers of samples.

Trial Registration

ClinicalTrials.gov NCT00003835

Clinical problems of colorectal cancer and endometrial cancer cases with unknown cause of tumor mismatch repair deficiency (suspected Lynch syndrome)

Carriers of a germline mutation in one of the DNA mismatch repair (MMR) genes have a high risk of developing numerous different cancers, predominantly colorectal cancer and endometrial cancer (known as Lynch syndrome). MMR gene mutation carriers develop tumors with MMR deficiency identified by tumor microsatellite instability or immunohistochemical loss of MMR protein expression. Tumor MMR deficiency is used to identify individuals most likely to carry an MMR gene mutation. However, MMR deficiency can also result from somatic inactivation, most commonly methylation of the MLH1 gene promoter. As tumor MMR testing of all incident colorectal and endometrial cancers (universal screening) is becoming increasingly adopted, a growing clinical problem is emerging for individuals who have tumors that show MMR deficiency who are subsequently found not to carry an MMR gene mutation after genetic testing using the current diagnostic approaches (Sanger sequencing and multiplex ligation-dependent probe amplification) and who also show no evidence of MLH1 methylation. The inability to determine the underlying cause of tumor MMR deficiency in these “Lynch-like” or “suspected Lynch syndrome” cases has significant implications on the clinical management of these individuals and their relatives. When the data from published studies are combined, 59% (95% confidence interval [CI]: 55% to 64%) of colorectal cancers and 52% (95% CI: 41% to 62%) of endometrial cancers with MMR deficiency were identified as suspected Lynch syndrome. Recent studies estimated that colorectal cancer risk for relatives of suspected Lynch syndrome cases is lower than for relatives of those with MMR gene mutations, but higher than for relatives of those with tumor MMR deficiency resulting from methylation of the MLH1 gene promoter. The cause of tumor MMR deficiency in suspected Lynch syndrome cases is likely due to either unidentified germline MMR gene mutations, somatic cell mosaicism, or biallelic somatic inactivation. Determining the underlying cause of tumor MMR deficiency in suspected Lynch syndrome cases is likely to reshape the current triaging schemes used to identify germline MMR gene mutations in cancer-affected individuals and their relatives.