Comprehensive molecular characterization of human colon and rectal cancer

Abstract

To characterize somatic alterations in colorectal carcinoma, we conducted a genome-scale analysis of 276 samples, analysing exome sequence, DNA copy number, promoter methylation and messenger RNA and microRNA expression. A subset of these samples (97) underwent low-depth-of-coverage whole-genome sequencing. In total, 16% of colorectal carcinomas were found to be hypermutated: three-quarters of these had the expected high microsatellite instability, usually with hypermethylation and MLH1 silencing, and one-quarter had somatic mismatch-repair gene and polymerase ε (POLE) mutations. Excluding the hypermutated cancers, colon and rectum cancers were found to have considerably similar patterns of genomic alteration. Twenty-four genes were significantly mutated, and in addition to the expected APC, TP53, SMAD4, PIK3CA and KRAS mutations, we found frequent mutations in ARID1A, SOX9 and FAM123B. Recurrent copy-number alterations include potentially drug-targetable amplifications of ERBB2 and newly discovered amplification of IGF2. Recurrent chromosomal translocations include the fusion of NAV2 and WNT pathway member TCF7L1. Integrative analyses suggest new markers for aggressive colorectal carcinoma and an important role for MYC-directed transcriptional activation and repression. The Cancer Genome Atlas consortium reports on their genome-wide characterization of somatic alterations in colorectal cancer; in addition to revealing a remarkably consistent pattern of genomic alteration, with 24 genes being significantly mutated, the study identifies new targets for therapeutic intervention and suggests an important role for MYC-directed transcriptional activation and repression. The Cancer Genome Atlas consortium reports on their genome-wide characterization of somatic alterations in colorectal carcinoma. Combined analysis of exome sequence data, DNA copy number, promoter methylation, messenger RNA and microRNA expression, as well as low-coverage whole-genome sequencing reveal that 16% of these carcinomas have hypermutation. Of these, three-quarters have the expected high microsatellite instability, but the rest have somatic mismatch repair gene mutations. The data reveal a remarkably consistent pattern of genomic alteration, with 24 genes being significantly mutated. As well as identifying new biomarkers for aggressive colorectal carcinoma, the data imply an important role for MYC-directed transcriptional activation and repression.

The authors' abstract, as published at the source. Nature, 2012 · DOI ↗