Distribution of the c-myc oncoprotein in normal and neoplastic tissues of the rat colon.

A rat model of 5-azoxymethane induced colon cancer was studied in order to correlate histopathological changes and the differential distribution of the c-myc protein. Weanling Fisher 344 rats were injected with three, one week apart, subcutaneous injections of 5-azoxymethane (AOM) (15 mg kg-1) and the animals were divided into low and high fat diet groups. Nine colon tumors, of varying degrees of malignancy, that developed in the AOM-treated rats, and sections of normal colonic mucosa were examined. A rabbit polyclonal anti-c-myc antibody produced nuclear staining at 1:100 dilution in cryostat frozen sections of the normal rat colonic mucosa and the colon tumors when prepared with a Cryostat Frozen Sectioning Aid (CFSA). The tissue localization of the c-myc antibody staining revealed: (1) in normal mucosa, nuclei of the basal portion of the mucosa; (2) in adenomatous polyps, nuclei at all levels of the mucosa; and (3) in a carcinoma in situ, intense staining of glandular epithelial cell nuclei at all levels within the tumor. This procedure may provide a sensitive method for detecting abnormal cells in the colonic epithelium that have an altered proliferative capacity.