CancerQuest >> Cancer by Type >> Colon and Rectal Cancer

Colon and Rectal Cancer: Tumor Biology I

Mutation (or epigenetic modification) of key genes alters the behavior of cancer cells. The genetic alterations lead to changes in protein products and changes in the amount of product produced by genes (gene expression). As changes accumulate, the cells become more abnormal and cancer progresses. Details about these changes can be found in the Genetic Change chapter of this site. Some of the genes that have been shown to be important in the development of colorectal cancer are listed below and discussed on the following pages:

• APC Gene
• TP53 Gene
• MSH2 and MLH1 Genes
• K-Ras Gene

APC Gene

APC (adenomatous polyposis coli) is a tumor suppressor gene that plays a role in cell signaling. Mutation in APC is thought to be an important step in the initial formation of adenomas. Inherited APC mutations result in familial adenomatous polyposis (FAP), a disorder characterized by the growth of hundreds to thousands of polyps along the lining of the colon.

Learn more about APC and cancer development
Learn more about familial adenomatous polyposis (FAP)

Acquired adenomas in the right colon: Two of the larger lesions have developed stalks that connect the neoplastic "head" of the polyp to the mucosal surface. Polyps with stalks are called "pedunculated".
(Image courtesy of: C. Whitaker Sewell, MD - Professor of Pathology, Emory University School of Medicine)

Pedunculated adenoma of the colon: The berry-like "head" of the polyp is the neoplastic portion; the long stalk is composed of normal tissue, and contains the blood supply. (Image courtesy of: C. Whitaker Sewell, MD - Professor of Pathology, Emory University School of Medicine)

Low power microscopic image of a pedunculated adenoma: The darker staining cells in the head of the polyp represent the mutated neoplastic cells; the stalk is lined by normal colonic mucosa and contains the vascular supply. (Image courtesy of: C. Whitaker Sewell, MD - Professor of Pathology, Emory University School of Medicine)