Bcl9 and Pygo synergise downstream of Apc to effect intestinal neoplasia in FAP mouse models.

Bcl9 and Pygo are Wnt enhanceosome components that effect β-catenin-dependent transcription. Whether they mediate β-catenin-dependent neoplasia is unclear. Here we assess their roles in intestinal tumourigenesis initiated by Apc loss-of-function (Apc), or by Apc encoding a partially-functional Apc truncation commonly found in colorectal carcinomas.

Molecular pathological classification of colorectal cancer.

Colorectal cancer (CRC) shows variable underlying molecular changes with two major mechanisms of genetic instability: chromosomal instability and microsatellite instability. This review aims to delineate the different pathways of colorectal carcinogenesis and provide an overview of the most recent advances in molecular pathological classification systems for colorectal cancer. Two molecular pathological classification systems for CRC have recently been proposed.

Detection of colorectal dysplasia using fluorescently labelled lectins.

Colorectal cancer screening using conventional colonoscopy lacks molecular information and can miss dysplastic lesions. We tested here the ability of fluorescently labelled lectins to distinguish dysplasia from normal tissue when sprayed on to the luminal surface epithelium of freshly resected colon tissue from the Apc(min) mouse and when applied to fixed human colorectal tissue sections. Wheat germ agglutinin (WGA) showed significantly decreased binding to adenomas in the mouse tissue and in sections of human colon from 47 patients.

Boosting Wnt activity during colorectal cancer progression through selective hypermethylation of Wnt signaling antagonists.

Background: There is emerging evidence that Wnt pathway activity may increase during the progression from colorectal adenoma to carcinoma and that this increase is potentially an important step towards the invasive stage. Here, we investigated whether epigenetic silencing of Wnt antagonists is the biological driver for this increased Wnt activity in human tissues and how these methylation changes correlate with MSI (Microsatelite Instability) and CIMP (CpG Island Methylator Phenotype) statuses as well as known mutations in genes driving colorectal neoplasia.

Methods: We conducted a systematic analysis by pyrosequencing, to determine the promoter methylation of CpG islands associated with 17 Wnt signaling component genes.

LEF1 and B9L shield β-catenin from inactivation by Axin, desensitizing colorectal cancer cells to tankyrase inhibitors.

Hyperactive β-catenin drives colorectal cancer, yet inhibiting its activity remains a formidable challenge. Interest is mounting in tankyrase inhibitors (TNKSi), which destabilize β-catenin through stabilizing Axin. Here, we confirm that TNKSi inhibit Wnt-induced transcription, similarly to carnosate, which reduces the transcriptional activity of β-catenin by blocking its binding to BCL9, and attenuates intestinal tumors in Apc(Min) mice.

Wild-type K-ras has a tumour suppressor effect on carcinogen-induced murine colorectal adenoma formation.

K-ras mutations are found in ~40% of human colorectal adenomas and carcinomas and contribute to colorectal tumour formation at an early stage. Wild-type K-ras has been reported to be deleted in some tumours, but the consequences of changes in wild-type K-ras copy number for experimental colorectal carcinogenesis have not been investigated. To characterize the effects of K-ras copy number changes on formation of carcinogen-induced colorectal neoplasms in mice, wild-type (K-ras(+/+) ) and heterozygous K-ras exon 1 knockout (K-ras(+/-) ) mice were given 10 weekly treatments of 1, 2-dimethylhydrazine (DMH) to induce colorectal tumours.

IRS2 is a candidate driver oncogene on 13q34 in colorectal cancer.

Copy number alterations are frequently found in colorectal cancer (CRC), and recurrent gains or losses are likely to correspond to regions harbouring genes that promote or impede carcinogenesis respectively. Gain of chromosome 13q is common in CRC but, because the region of gain is frequently large, identification of the driver gene(s) has hitherto proved difficult. We used array comparative genomic hybridization to analyse 124 primary CRCs, demonstrating that 13q34 is a region of gain in 35% of CRCs, with focal gains in 4% and amplification in a further 1.

Sequential DNA methylation changes are associated with DNMT3B overexpression in colorectal neoplastic progression.

Background And Aims: Although aberrant methylation of key genes in the progression of colorectal neoplasia has been reported, no model-based analysis of the incremental changes through the intermediate adenoma stage has been described. In addition, the biological drivers for these methylation changes have yet to be defined. Linear mixed-effects modelling was used in this study to understand the onset and patterns of the methylation changes of SFRP2, IGF2 DMR0, H19, LINE-1 and a CpG island methylator phenotype (CIMP) marker panel, and they were correlated with DNA methyltransferase 3B (DNMT3B) levels of expression in a sample set representative of colorectal neoplastic progression.

Dvl2 promotes intestinal length and neoplasia in the ApcMin mouse model for colorectal cancer.

APC mutations cause activation of Wnt/beta-catenin signaling, which invariably leads to colorectal cancer. Similarly, overexpressed Dvl proteins are potent activators of beta-catenin signaling. Screening a large tissue microarray of different staged colorectal tumors by immunohistochemistry, we found that Dvl2 has a strong tendency to be overexpressed in colorectal adenomas and carcinomas, in parallel to nuclear beta-catenin and Axin2 (a universal transcriptional target of Wnt/beta-catenin signaling).

Somatically acquired hypomethylation of IGF2 in breast and colorectal cancer.

The imprinted insulin-like growth factor 2 (IGF2) gene is expressed predominantly from the paternal allele. Loss of imprinting (LOI) associated with hypomethylation at the promoter proximal sequence (DMR0) of the IGF2 gene was proposed as a predisposing constitutive risk biomarker for colorectal cancer. We used pyrosequencing to assess whether IGF2 DMR0 methylation is either present constitutively prior to cancer or whether it is acquired tissue-specifically after the onset of cancer.

The extracellular matrix protein TGFBI induces microtubule stabilization and sensitizes ovarian cancers to paclitaxel.

The extracellular matrix (ECM) can induce chemotherapy resistance via AKT-mediated inhibition of apoptosis. Here, we show that loss of the ECM protein TGFBI (transforming growth factor beta induced) is sufficient to induce specific resistance to paclitaxel and mitotic spindle abnormalities in ovarian cancer cells. Paclitaxel-resistant cells treated with recombinant TGFBI protein show integrin-dependent restoration of paclitaxel sensitivity via FAK- and Rho-dependent stabilization of microtubules.

High-throughput methylation profiling by MCA coupled to CpG island microarray.

An abnormal pattern of DNA methylation occurs at specific genes in almost all neoplasms. The lack of high-throughput methods with high specificity and sensitivity to detect changes in DNA methylation has limited its application for clinical profiling. Here we overcome this limitation and present an improved method to identify methylated genes genome-wide by hybridizing a CpG island microarray with amplicons obtained by the methylated CpG island amplification technique (MCAM).

LINE-1 hypomethylation in cancer is highly variable and inversely correlated with microsatellite instability.

Background: Alterations in DNA methylation in cancer include global hypomethylation and gene-specific hypermethylation. It is not clear whether these two epigenetic errors are mechanistically linked or occur independently. This study was performed to determine the relationship between DNA hypomethylation, hypermethylation and microsatellite instability in cancer.

MMASS: an optimized array-based method for assessing CpG island methylation.

We describe an optimized microarray method for identifying genome-wide CpG island methylation called microarray-based methylation assessment of single samples (MMASS) which directly compares methylated to unmethylated sequences within a single sample. To improve previous methods we used bioinformatic analysis to predict an optimized combination of methylation-sensitive enzymes that had the highest utility for CpG-island probes and different methods to produce unmethylated representations of test DNA for more sensitive detection of differential methylation by hybridization. Subtraction or methylation-dependent digestion with McrBC was used with optimized (MMASS-v2) or previously described (MMASS-v1, MMASS-sub) methylation-sensitive enzyme combinations and compared with a published McrBC method.