Colon Cancer In Men - Essay Example

APC gene encodes a protein that targets degradation of beta-catenin, a protein component of a transcriptional complex that activates growth-promoting oncogenes, such as cyclin D1 or c-myc. In mutation, the earliest event is DNA methylation and this can be detected even at the polyp stage. This leads to global hypomethylation and regional hypermethylation. While hypomethylation leads to oncogene activation, hypermethylation contributes to silencing of tumor supressor genes. One important mutation is ras gene mutation which is commonly noted in larger polyps and not in smaller polyps prompting the role of this mutated gene in polyp growth.

Other mutations include chromosome arm 18q deletions, chromosome arm 17p losses, tumor suppressor p53 mutations, Bc12 over expression and 18q deletions. Chromosome arm 18q deletions are likely to involve the targets DPC4 (a gene deleted in pancreatic cancer and involved in the transforming growth factor [TGF]-beta growth-inhibitory signaling pathway) and DCC (a gene frequently deleted in colon cancer). While Bc12 over expression is an early event in colon cancer, chromosome arm 17p losses and tumor suppressor p53 mutations are late events.

18q deletions detected in Dukes stage B colon cancers are associated with an increased risk of recurrence following surgery (El- Deiry, Emedicine). Rarely adenocarcinoma of the colon is predisposed by hereditary nonpolyposis colon cancer. Individuals affected by this condition inherit a mutation in one of several genes involved in DNA mismatch repair, including MSH2, MLH1, and PMS2 (El- Deiry, Emedicine). The most common presenting complaint in colon cancer is abdominal pain which is noted in 50% of the cases.

Other clinical presentations include altered bowel habits, occult bleeding and intestinal obstruction. Colon cancer is often detected by screening (Winawer wt al, 1997, p.594), when this is done in those with