Rectal And Colon Cancer Based On Same Genomic Alterations

Rectal And Colon Cancer

According to The Cancer Genome Atlas (TCGA) project’s large-scale study of colon and rectal cancer tissue specimens, rectal cancer and colon cancer are based on the same genomic alterations. Researchers have realized this fact after they conducted a study on 224 colorectal cancer specimens. The study, funded by the National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI), provides a better understanding of the origin of colorectal cancer and may be the basis for new therapies to treat cancer. Harold E. Varmus, M.D., NCI director, said: “This genetic information unquestionably will be the springboard for determining what will be useful clinically against colorectal cancers.”

Genetic Cancer

Colorectal cancer is the most common digestive cancers and the fourth most common cancer in both men and women, after non-melanoma skin cancer, prostate cancer (breast) and lung. It is already known that colorectal cancer is based on two important risk factors: genetic alterations and adenomatous polyps. Adenomatous polyps are considered premalignant lesions and their malignant risk is even higher as the adenoma is higher. In genetic terms, the three types of key genes involved in colorectal cancer are: protooncogenes, those that coordinate cell proliferation, tumor suppressor genes and genes involved in repairing mutations that occur during replication.

Researchers noted that several genetic errors are recurrent in colorectal cancer. It was also found that in colorectal cancer there is a phenomenon of hypermutation. Because the mechanisms that should repair mutations occurred during replication are deficient, the degree of mutation is high. The researchers also noticed that, of the 224 colorectal cancers analyzed, 24 gene mutations occur in a significant number of cases. In addition to mutations known from previous studies, there have been found new ones (ARID1A, Sox9 and FAM123B/WTX).

As with other cancers, colorectal cancer involves the interaction of various factors such as genetic predisposition, individual predisposing conditions and environmental factors. Among environmental factors, it was found that high-fat diet is an important risk factor. Also, red meat intake, physical inactivity and obesity seems to predispose to colorectal cancer. In terms of individual predisposing conditions, age over 50 years, personal history of adenomas, history of inflammatory bowel disease (Crohn’s disease and ulcerative colitis), are risk factors for colorectal cancer. Regarding heredity, 25% of colorectal cancers have positive family history of disease. It is important to remember is that if detected early, colorectal cancer is curable. This is why colonoscopy  is recommended every 5 years among people aged over 50 years.