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Study Shows Colon and Rectal Tumors Are Same Type of Cancer

Initially, the TCGA Research Network studied colon tumors as distinct from rectal tumors.

"This finding of the true genetic nature of colon and rectal cancers is an important achievement in our quest to understand the foundations of this disease," said National Institutes of Health (NIH) Director Francis S. Collins, MD, PhD. "The data and knowledge gained here have the potential to change the way we diagnose and treat certain cancers."

The investigators 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), both parts of the NIH, was published online in the July 19 issue of Nature.

The NCI estimates that more than 143,000 people in the U.S. will be diagnosed with colorectal cancer and that 51,500 are likely to die from the disease in 2012. Colorectal cancer is the fourth most common cancer in men, after non-melanoma skin, prostate, and lung cancer. It is also the fourth most common cancer in women, after non-melanoma skin, breast, and lung cancer.

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 colorectal cancer when mutated.

The TCGA Research Network also identified the genes ERBB2 and IGF2 as mutated or over-expressed in colorectal cancer and as potential drug targets. These genes are involved in regulating cell proliferation and were observed to be frequently over-expressed in colorectal tumors. This finding points to a potential drug therapy strategy in which inhibition of the products of these genes would slow progression of the cancer.

Another key part of this study was the analysis of signaling pathways. Signaling pathways control gene activity during cell development and regulate the interactions between cells as they form organs or tissues. Among other findings, the TCGA Research Network identified new mutations in a particular signaling cascade called the WNT pathway. According to the researchers, this finding will improve the development of WNT signaling inhibitors, which have shown promise as a class of drugs that could benefit patients with colorectal cancer.

For more information, visit the NIH Web site.

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