Screening for ROS1 gene rearrangements in non-small-cell lung cancers using immunohistochemistry with FISH confirmation is an effective method to identify this rare target.

AIMS: To assess the prevalence of ROS1 rearrangements in a retrospective and prospective diagnostic Australian cohort and evaluate the effectiveness of immunohistochemical screening. METHODS AND RESULTS: A retrospective cohort of 278 early stage lung adenocarcinomas and an additional 104 prospective non-small-cell lung cancer (NSCLC) cases referred for routine molecular testing were evaluated. ROS1 immunohistochemistry (IHC) was performed (D4D6 clone, Cell Signaling Technology) on all cases as well as fluorescence in-situ hybridization (FISH) using the ZytoVision and Abbott Molecular ROS1 FISH probes, with ≥15% of cells with split signals considered positive for rearrangement. Eighty-eight cases (32%) from the retrospective cohort showed staining by ROS1 IHC, and one case (0.4%) showed ROS1 rearrangement by FISH. Nineteen of the prospective diagnostic cases showed ROS1 IHC staining, 12 (12%) cases of which were confirmed as ROS1 rearranged by FISH. There were no ROS1 rearranged cases that showed no expression of ROS1 with IHC. The ROS1 rearranged cases in the prospective cohort were all EGFR wild-type and anaplastic lymphoma kinase (ALK) rearrangement-negative. The sensitivity of ROS1 IHC in the retrospective cohort was 100% and specificity was 76%. CONCLUSIONS: ROS1 rearrangements are rare events in lung adenocarcinomas. Selection of cases for ROS1 FISH testing, by excluding EGFR/ALK-positive cases and use of IHC to screen for potentially positive cases, can be used to enrich for the likelihood of identifying a ROS1 rearranged lung cancer and prevent the need to undertake expensive and time-consuming FISH testing in all cases.

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

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

Proteogenomic Analysis Identifies a Novel Human SHANK3 Isoform.

Mutations of the SHANK3 gene have been associated with autism spectrum disorder. Individuals harboring different SHANK3 mutations display considerable heterogeneity in their cognitive impairment, likely due to the high SHANK3 transcriptional diversity. In this study, we report a novel interaction between the Mutated in colorectal cancer (MCC) protein and a newly identified SHANK3 protein isoform in human colon cancer cells and mouse brain tissue. Hence, our proteogenomic analysis identifies a new human long isoform of the key synaptic protein SHANK3 that was not predicted by the human reference genome. Taken together, our findings describe a potential new role for MCC in neurons, a new human SHANK3 long isoform and, importantly, highlight the use of proteomic data towards the re-annotation of GC-rich genomic regions.

KRAS mutations and CDKN2A promoter methylation show an interactive adverse effect on survival and predict recurrence of rectal cancer.

Colonic and rectal cancers differ in their clinicopathologic features and treatment strategies. Molecular markers such as gene methylation, microsatellite instability and KRAS mutations, are becoming increasingly important in guiding treatment decisions in colorectal cancer. However, their association with clinicopathologic variables and utility in the management of rectal cancer is still poorly understood. We analyzed CDKN2A gene methylation, CpG island methylator phenotype (CIMP), microsatellite instability and KRAS/BRAF mutations in a cohort of 381 rectal cancers with extensive clinical follow-up data. BRAF mutations (2%), CIMP-high (4%) and microsatellite instability-high (2%) were rare, whereas KRAS mutations (39%), CDKN2A methylation (20%) and CIMP-low (25%) were more common. Only CDKN2A methylation and KRAS mutations showed an association with poor overall survival but these did not remain significant when analyzed with other clinicopathologic factors. In contrast, this prognostic effect was strengthened by the joint presence of CDKN2A methylation and KRAS mutations, which independently predicted recurrence of cancer and was associated with poor overall and cancer-specific survival. This study has identified a subgroup of more aggressive rectal cancers that may arise through the KRAS-p16 pathway. It has been previously shown that an interaction of p16 deficiency and oncogenic KRAS promotes carcinogenesis in the mouse and is characterized by loss of oncogene-induced senescence. These findings may provide avenues for the discovery of new treatments in rectal cancer.

Loss of special AT-rich sequence-binding protein 1 (SATB1) predicts poor survival in patients with colorectal cancer.

AIM: Special AT-rich sequence-binding protein 1 (SATB1) is a cell type-specific matrix attachment region binding protein, functioning as a global genome organizer. This study aims to investigate the expression pattern and the prognostic value of SATB1 in colorectal cancer. METHODS AND RESULTS: Prospectively collected data were obtained and tissue microarrays were constructed from a cohort of 352 patients. SATB1 protein expression was evaluated by immunohistochemistry and scored by two independent investigators. SATB1 expression was predominantly nuclear in both normal and cancer tissues. Loss of SATB1 nuclear expression was seen in 22% of colorectal cancers compared to 1.5% of adjacent normal colorectal tissue, and was associated with worse overall survival (P = 0.02) independent of age and stage of disease (HR 2.48 with 95% CI 1.31-4.70). Loss of SATB1 expression was more evident in younger patients (P = 0.03), tumours with mucinous or signet ring histology (P = 0.0001) and poor differentiation (P = 0.005). SATB1 expression was associated with a survival advantage in patients with Dukes C tumours who received adjuvant chemotherapy. CONCLUSION: Loss of SATB1 nuclear expression correlates with poor survival and a less favourable response to adjuvant chemotherapy in colorectal cancer. The value of SATB1 in individualized colorectal cancer therapy warrants further evaluation.

The PDZ-binding motif of MCC is phosphorylated at position -1 and controls lamellipodia formation in colon epithelial cells.

In this study, we describe a new post-translational modification at position -1 of the PDZ-binding motif in the mutated in colorectal cancer (MCC) protein and its role in lamellipodia formation. Serine 828 at position -1 of this motif is phosphorylated, which is predicted to increase MCC binding affinity with the polarity protein Scrib. We show that endogenous MCC localizes at the active migratory edge of cells, where it interacts with Scrib and the non-muscle motor protein Myosin-IIB. Expression of MCC harboring a phosphomimetic mutation MCC-S828D strongly impaired lamellipodia formation and resulted in accumulation of Myosin-IIB in the membrane cortex fraction. We propose that MCC regulates lamellipodia formation by binding to Scrib and its downstream partner Myosin-IIB in a multiprotein complex. Importantly, we propose that the function of this complex is under the regulation of a newly described phosphorylation of the PDZ-binding motif at position -1.

Beyond the genomics blueprint: the 4th Human Variome Project Meeting, UNESCO, Paris, 2012.

The 4th Biennial Meeting of the Human Variome Project Consortium was held at the headquarters of the United Nations Educational, Scientific and Cultural Organization (UNESCO) in Paris, 11-15 June 2012. The Human Variome Project, a nongovernmental organization and an official partner of UNESCO, enables the routine collection, curation, interpretation, and sharing of information on all human genetic variation. This meeting was attended by more than 180 delegates from 39 countries and continued the theme of addressing issues of implementation in this unique project. The meeting was structured around the four main themes of the Human Variome Project strategic plan, "Project Roadmap 2012-2016": setting normative function, behaving ethically, sharing knowledge, and building capacity. During the meeting, the members held extensive discussions to formulate an action plan in the key areas of the Human Variome Project. The actions agreed on were promulgated at the Project's two Advisory Council and Scientific Advisory Committee postconference meetings.

Sulindac activates NF-κB signaling in colon cancer cells.

BACKGROUND: The non-steroidal anti-inflammatory drug (NSAID) sulindac has shown efficacy in preventing colorectal cancer. This potent anti-tumorigenic effect is mediated through multiple cellular pathways but is also accompanied by gastrointestinal side effects, such as colon inflammation. We have recently shown that sulindac can cause up-regulation of pro-inflammatory factors in the mouse colon mucosa. The aim of this study was to determine the signaling pathways that mediate the transcriptional activation of pro-inflammatory cytokines in colon cancer epithelial cells treated with sulindac sulfide. RESULTS: We found that sulindac sulfide increased NF-κB signaling in HCT-15, HCT116, SW480 and SW620 cells, although the level of induction varied between cell lines. The drug caused a decrease in IκBα levels and an increase of p65(RelA) binding to the NF-κB DNA response element. It induced expression of IL-8, ICAM1 and A20, which was inhibited by the NF-κB inhibitor PDTC. Sulindac sulfide also induced activation of the AP-1 transcription factor, which co-operated with NF-κB in up-regulating IL-8. Up-regulation of NF-κB genes was most prominent in conditions where only a subset of cells was undergoing apoptosis. In TNFα stimulated conditions the drug treatment inhibited phosphorylation on IκBα (Ser 32) which is consistent with previous studies and indicates that sulindac sulfide can inhibit TNFα-induced NF-κB activation. Sulindac-induced upregulation of NF-κB target genes occurred early in the proximal colon of mice given a diet containing sulindac for one week. CONCLUSIONS: This study shows for the first time that sulindac sulfide can induce pro-inflammatory NF-κB and AP-1 signaling as well as apoptosis in the same experimental conditions. Therefore, these results provide insights into the effect of sulindac on pro-inflammatory signaling pathways, as well as contribute to a better understanding of the mechanism of sulindac-induced gastrointestinal side effects.

A STAT3 protein complex required for mitochondrial mRNA stability and cancer.

Signal transducer and activator of transcription 3 (STAT3) is a potent transcription factor necessary for life whose activity is corrupted in diverse diseases, including cancer. STAT3 biology was presumed to be entirely dependent on its activity as a transcription factor until the discovery of a mitochondrial pool of STAT3, which is necessary for normal tissue function and tumorigenesis. However, the mechanism of this mitochondrial activity remained elusive. This study uses immunoprecipitation and mass spectrometry to identify a complex containing STAT3, leucine-rich pentatricopeptide repeat containing (LRPPRC), and SRA stem-loop-interacting RNA-binding protein (SLIRP) that is required for the stability of mature mitochondrially encoded mRNAs and transport to the mitochondrial ribosome. Moreover, we show that this complex is enriched in patients with lung adenocarcinoma and that its deletion inhibits the growth of lung cancer in vivo, providing therapeutic opportunities through the specific targeting of the mitochondrial activity of STAT3.

The NSAID sulindac is chemopreventive in the mouse distal colon but carcinogenic in the proximal colon.

BACKGROUND AND AIMS: The non-steroidal anti-inflammatory drug sulindac is an effective chemopreventive agent in sporadic colorectal cancer but its potential benefit in mismatch repair deficient cancers remains to be defined. We wanted to determine whether genetic defects that are relevant for colorectal cancer, such as Msh2 or p53 deficiency, would influence the efficiency of sulindac chemoprevention or increase the side effects. METHODS: Msh2 or p53 deficient and wild-type mice received feed containing 160-320 ppm sulindac for up to 25 weeks with or without a concurrent treatment with the carcinogen azoxymethane. Colon tissue was analysed by histopathology and molecular biology methods. RESULTS: We show that sulindac prevented azoxymethane-induced distal colon tumours in all mice. In the proximal colon, however, sulindac induced new inflammatory lesions on the mucosal folds, which further developed into adenocarcinoma in up to 18-25% of the p53 or Msh2 deficient mice but rarely in wild-type mice. This region in the proximal colon was characterised by a distinct profile of pro- and anti-inflammatory factors, which were modulated by the sulindac diet, including upregulation of hypoxia inducible factor 1α and macrophage inflammatory protein 2. CONCLUSIONS: These data show that the sulindac diet promotes carcinogenesis in the mouse proximal colon possibly through chronic inflammation. Sulindac has both beneficial and harmful effects in vivo, which are associated with different microenvironments within the colon of experimental mice. Deficiency for the Msh2 or p53 tumour suppressor genes increases the harmful side effects of long-term sulindac treatment in the mouse colon.

Antibiotic exposure within six months before systemic therapy was associated with lower cancer survival.

OBJECTIVES: The objective of the study was to quantify associations between cancer survival and antibiotic exposure before systemic anticancer therapy. STUDY DESIGN AND SETTING: This population-based cohort study compares cause-specific survival according to antibiotic exposure before non-immune checkpoint inhibitor (ICI) systemic therapy in patients diagnosed with single primary cancers in New South Wales between 2013 and 2016. Proportional hazards regression was used to control for confounding, with no antibiotic exposure in the six months before non-ICI systemic therapy serving as the comparator. RESULTS: After adjusting for tumour spread, cancer site, age, sex and comorbidity, people having antibiotic exposure within 180 days before non-ICI systemic therapy had poorer cancer survival (hazard ratios ranging from 1.21 [95% confidence interval: 1.06-1.39] to 1.58 [1.34-1.87]) for shorter periods since antibiotic exposure (P < .0001). Similarly, poorer survival trends applied for localized and metastatic cancer. Of six prevalent cancers studied, lung and breast primaries showed the strongest associations of lower survival with prior antibiotic exposure. CONCLUSION: Antibiotic exposure within 180 days before non-ICI systemic cancer treatment is associated with poorer survival. If confirmed in other studies, it provides another reason for vigilant antibiotic stewardship.

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

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

The emerging role of the lung microbiome and its importance in non-small cell lung cancer diagnosis and treatment.

Over the last 10 years, with the development of culture-free bacterial identification techniques, understanding of how the microbiome influences diseases has increased exponentially and has highlighted potential opportunities for its use as a diagnostic biomarker and interventional target in many diseases including malignancy. Initial research focused on the faecal microbiome since it contains the densest bacterial populations and many other mucosal sites, such as the lungs, were until recently thought to be sterile. However, in recent years, it has become clear that the lower airways are home to a dynamic bacterial population sustained by the migration and elimination of microbes from the gastrointestinal and upper airway tracts. As in the gut, the lung microbiome plays an important role in regulating mucosal immunity and maintaining the balance between immune tolerance and inflammation. Studies to date have all shown that the lung microbiome undergoes significant changes in the setting of pulmonary disease. In lung cancer, animal models and small patient cohort studies have suggested that microbiome dysbiosis may not only impact tumour progression and response to therapy, particularly immunotherapy, but also plays a key role in cancer pathogenesis by influencing early carcinogenic pathways. These early results have led to concerted efforts to identify microbiome signatures that represent diagnostic biomarkers of early-stage disease and to consider modulation of the lung microbiome as a potential therapeutic strategy. Lung microbiome research is in its infancy and studies to date have been small, single centre with significant methodological variation. Large, multicentre longitudinal studies are needed to establish the clinical potential of this exciting field.

Deciphering the colon cancer genes--report of the InSiGHT-Human Variome Project Workshop, UNESCO, Paris 2010.

The Human Variome Project (HVP) has established a pilot program with the International Society for Gastrointestinal Hereditary Tumours (InSiGHT) to compile all inherited variation affecting colon cancer susceptibility genes. An HVP-InSiGHT Workshop was held on May 10, 2010, prior to the HVP Integration and Implementation Meeting at UNESCO in Paris, to review the progress of this pilot program. A wide range of topics were covered, including issues relating to genotype-phenotype data submission to the InSiGHT Colon Cancer Gene Variant Databases (chromium.liacs.nl/LOVD2/colon_cancer/home.php). The meeting also canvassed the recent exciting developments in models to evaluate the pathogenicity of unclassified variants using in silico data, tumor pathology information, and functional assays, and made further plans for the future progress and sustainability of the pilot program.

Tetranucleotide and Low Microsatellite Instability Are Inversely Associated with the CpG Island Methylator Phenotype in Colorectal Cancer.

MSH3 gene or protein deficiency or loss-of-function in colorectal cancer can cause a DNA mismatch repair defect known as "elevated microsatellite alterations at selected tetranucleotide repeats" (EMAST). A high percentage of MSI-H tumors exhibit EMAST, while MSI-L is also linked with EMAST. However, the distribution of CpG island methylator phenotype (CIMP) within the EMAST spectrum is not known. Five tetranucleotide repeat and five MSI markers were used to classify 100 sporadic colorectal tumours for EMAST, MSI-H and MSI-L according to the number of unstable markers detected. Promoter methylation was determined using methylation-specific PCR for MSH3, MCC, CDKN2A (p16) and five CIMP marker genes. EMAST was found in 55% of sporadic colorectal carcinomas. Carcinomas with only one positive marker (EMAST-1/5, 26%) were associated with advanced tumour stage, increased lymph node metastasis, MSI-L and lack of CIMP-H. EMAST-2/5 (16%) carcinomas displayed some methylation but MSI was rare. Carcinomas with ≥3 positive EMAST markers (13%) were more likely to have a proximal colon location and be MSI-H and CIMP-H. Our study suggests that EMAST/MSI-L is a valuable prognostic and predictive marker for colorectal carcinomas that do not display the high methylation phenotype CIMP-H.

How to catch all those mutations--the report of the third Human Variome Project Meeting, UNESCO Paris, May 2010.

The third Human Variome Project (HVP) Meeting "Integration and Implementation" was held under UNESCO Patronage in Paris, France, at the UNESCO Headquarters May 10-14, 2010. The major aims of the HVP are the collection, curation, and distribution of all human genetic variation affecting health. The HVP has drawn together disparate groups, by country, gene of interest, and expertise, who are working for the common good with the shared goal of pushing the boundaries of the human variome and collaborating to avoid unnecessary duplication. The meeting addressed the 12 key areas that form the current framework of HVP activities: Ethics; Nomenclature and Standards; Publication, Credit and Incentives; Data Collection from Clinics; Overall Data Integration and Access-Peripheral Systems/Software; Data Collection from Laboratories; Assessment of Pathogenicity; Country Specific Collection; Translation to Healthcare and Personalized Medicine; Data Transfer, Databasing, and Curation; Overall Data Integration and Access-Central Systems; and Funding Mechanisms and Sustainability. In addition, three societies that support the goals and the mission of HVP also held their own Workshops with the view to advance disease-specific variation data collection and utilization: the International Society for Gastrointestinal Hereditary Tumours, the Micronutrient Genomics Project, and the Neurogenetics Consortium.

Role of Lung Microbiome in Innate Immune Response Associated With Chronic Lung Diseases.

Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), lung fibrosis, and lung cancer, pose a huge socio-economic burden on society and are one of the leading causes of death worldwide. In the past, culture-dependent techniques could not detect bacteria in the lungs, therefore the lungs were considered a sterile environment. However, the development of culture-independent techniques, particularly 16S rRNA sequencing, allowed for the detection of commensal microbes in the lung and with further investigation, their roles in disease have since emerged. In healthy individuals, the predominant commensal microbes are of phylum Firmicutes and Bacteroidetes, including those of the genera Veillonella and Prevotella. In contrast, pathogenic microbes (Haemophilus, Streptococcus, Klebsiella, Pseudomonas) are often associated with lung diseases. There is growing evidence that microbial metabolites, structural components, and toxins from pathogenic and opportunistic bacteria have the capacity to stimulate both innate and adaptive immune responses, and therefore can contribute to the pathogenesis of lung diseases. Here we review the multiple mechanisms that are altered by pathogenic microbiomes in asthma, COPD, lung cancer, and lung fibrosis. Furthermore, we focus on the recent exciting advancements in therapies that can be used to restore altered microbiomes in the lungs.

Expression and prognostic significance of cyclin B1 and cyclin A in non-small cell lung cancer.

AIMS: Aberrant expression of cell cycle regulators has been implicated in the pathogenesis of many neoplasms, including non-small cell lung cancer (NSCLC). The aim was to examine the expression and prognostic value of cyclin B1 and cyclin A, key regulators of the G(2)/M checkpoint of the cell cycle, in NSCLC and bronchial precursor lesions. METHODS AND RESULTS: Immunohistochemical expression of cyclin B1 and A was examined in 90 cases of stage I-II primary NSCLC and bronchial precursor lesions using tissue microarrays. Increased cyclin B1 and A expression was found in 40.9 and 58.9% of NSCLC cases, respectively, and was significantly higher in primary NSCLC, lymph node metastases and some bronchial precursor lesions compared with normal bronchial epithelium. Increased expression of cyclin A and cyclin B1 correlated with tumour type, poorly differentiated tumours and male gender. A significant association was found between increased cyclin B1 expression and reduced survival using Kaplan-Meier survival analysis. On multivariate analysis, cyclin B1 was not an independent prognostic factor (P = 0.067). Cyclin A expression was not associated with survival. CONCLUSIONS: Cyclin B1 and cyclin A are aberrantly expressed in NSCLC and some precursor lesions. Cyclin B1, but not cyclin A, shows some promise as a potential prognostic marker in NSCLC.

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

BACKGROUND & AIMS: The early events by which inflammation promotes cancer are still not fully defined. The MCC gene is silenced by promoter methylation in colitis-associated and sporadic colon tumors, but its functional significance in precancerous lesions or polyps is not known. Here, we aimed to determine the impact of Mcc deletion on the cellular pathways and carcinogenesis associated with inflammation in the mouse proximal colon. METHODS: We generated knockout mice with deletion of Mcc in the colonic/intestinal epithelial cells (MccΔIEC) or in the whole body (MccΔ/Δ). Drug-induced lesions were analyzed by transcriptome profiling (at 10 weeks) and histopathology (at 20 weeks). Cell-cycle phases and DNA damage proteins were analyzed by flow cytometry and Western blot of hydrogen peroxide-treated mouse embryo fibroblasts. RESULTS: Transcriptome profiling of the lesions showed a strong response to colon barrier destruction, such as up-regulation of key inflammation and cancer-associated genes as well as 28 interferon γ-induced guanosine triphosphatase genes, including the homologs of Crohn's disease susceptibility gene IRGM. These features were shared by both Mcc-expressing and Mcc-deficient mice and many of the altered gene expression pathways were similar to the mesenchymal colorectal cancer subtype known as consensus molecular subtype 4 (CMS4). However, Mcc deletion was required for increased carcinogenesis in the lesions, with adenocarcinoma in 59% of MccΔIEC compared with 19% of Mcc-expressing mice (P = .002). This was not accompanied by hyperactivation of ß-catenin, but Mcc deletion caused down-regulation of DNA repair genes and a disruption of DNA damage signaling. CONCLUSIONS: Loss of Mcc may promote cancer through a failure to repair inflammation-induced DNA damage. We provide a comprehensive transcriptome data set of early colorectal lesions and evidence for the in vivo significance of MCC silencing in colorectal cancer.

Microsatellite Instability in Mouse Models of Colorectal Cancer.

Microsatellite instability (MSI) is caused by DNA mismatch repair deficiency and is an important prognostic and predictive biomarker in colorectal cancer but relatively few studies have exploited mouse models in the study of its clinical utility. Furthermore, most previous studies have looked at MSI in the small intestine rather than the colon of mismatch repair deficient Msh2-knockout (KO) mice. Here we compared Msh2-KO, p53-KO, and wild type (WT) mice that were treated with the carcinogen azoxymethane (AOM) and the nonsteroidal anti-inflammatory drug sulindac or received no treatment. The induced tumors and normal tissue specimens from the colon were analysed with a panel of five mononucleotide repeat markers. MSI was detected throughout the normal colon in untreated Msh2-KO mice and this involved contraction of the repeat sequences compared to WT. The markers with longer mononucleotide repeats (37-59) were the most sensitive for MSI while the markers with shorter repeats (24) showed only minor change. AOM exposure caused further contraction of the Bat37 and Bat59 repeats in the distal colon of Msh2-KO mice which was reversed by sulindac. Thus AOM-induced carcinogenesis is associated with increased instability of mononucleotide repeats in the colon of Msh2-KO mice but not in WT or p53-KO mice. Chemoprevention of these tumors by sulindac treatment reversed or prevented the increased MSI.