Blog | Friday, July 20, 2012

QD: News Every Day--Colon, rectal tumors genomically the same


Colon and rectal cancers share the same pattern of genomic alterations and can be grouped as one, according to The Cancer Genome Atlas (TCGA) project's large-scale study of colon and rectal cancer tissue specimens.

The study also found several of the recurrent genetic errors that contribute to colorectal cancer. The study, funded by the National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI), was published in Nature.

There is a known negative association between aggressiveness of colorectal tumors and the phenomenon of hypermutation, in which the rate of genetic mutation is abnormally high because normal DNA repair mechanisms are disrupted, the National Institutes of Health stated in a press release.

In this study, 16 percent of the specimens were found to be hypermutated. Three-fourths of these cases exhibited microsatellite instability (MSI), which often is an indicator for better prognosis. Microsatellites are repetitive sections of DNA in the genome. If mutations occur in the genes responsible for maintaining those regions of the genome, the microsatellites may become longer or shorter; this is called MSI.

The researchers observed that in the 224 colorectal cancer specimens examined, 24 genes were mutated in a significant numbers of cases. In addition to genes found through prior research efforts (e.g., APC, ARID1A, FAM123B/WTX, TP53, SMAD4, PIK3CA and KRAS), the scientists identified other genes (ARID1A, SOX9 and FAM123B/WTX) as potential drivers of this cancer when mutated.

Editor's Note: QD will resume on Monday, July 30.