Colon and Rectal Cancers - Causes

Biochemical Factors Involved in Colon and Rectal Cancers

Cyclooxygenases and Prostaglandins. Cyclooxygenase 1 and 2 (COX-1 and COX-2) are enzymes involved in the production of prostaglandins, substances produced by the body that cause inflammation, widen and narrow blood vessels, control muscle contractions, and inhibit hormones that regulate fat metabolism. COX-2, but not COX-1, appears to play a role in the development and spread of colorectal tumors. COX-2 increases the levels of prostaglandin E2 (PGE2), which, in turn, stimulates factors that inhibit apoptosis, the natural process whereby all cells, including cancerous ones, self-destruct. It also activates interleukin-6 (IL-6), a factor in the immune system that is associated with cancer cell invasion.

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C-Reactive Protein (CRP). CRP is another indicator of inflammation. In a case-control study published in the Journal of the American Medical Association (JAMA) in 2004, elevated CRP levels predicted the development of colon-- but not rectal-- cancer.

Bile Acid Salts. Deoxycholic acid, which is found in the fat-digesting bile salts released by the gallbladder, appears to have carcinogenic properties. Its effects are now believed to play a role in some cases of colon cancer. Levels of the acid can rise as a result of high-fat diets or certain diseases.

Growth Factors. Chronically higher circulating levels of growth factors, including insulin-like growth factor (IGF), have been associated with colorectal cancer.

Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) include Crohn's disease and ulcerative colitis. These chronic disorders cause persistent injuries in the intestinal tract that can, in some cases, produce cancerous changes.