Expression of cytokeratin subtypes in colorectal mucosa, adenoma, and carcinoma

The distribution pattern of cytokeratin (CK) subtypes, an intermediate filament of cytoskeleton, was examined in adenomas and carcinomas of the colon and rectum. For the detection of the cytokeratin subtypes, monoclonal antibodies to the 54 Kd keratin polypeptide (CK No. 7 according to Moll's classification), 52.5 Kd (CK No. 8), 45 Kd (CK No. 18), and 40 Kd (CK No. 19) were used for immunohistochemical observation. Although No. 7 was positive in normal mucosa and adenoma with mild to moderate atypia, it could not be recognized in carcinoma. On the other hand the expression of No. 18 was confirmed in carcinoma, adenoma, and normal mucosa, and there were some differences in its distribution pattern in those with or without glandular formation and in areas showing infiltration of tumor cells. No. 18 expression was on the luminal side of normal colonic mucosa, adenoma, and well-differentiated adenocarcinoma; in the infiltrating area its reactivity was localized diffusely in the cytoplasm of tumor cells showing moderately or poorly differentiated adenocarcinoma cells. As to No. 8 and No. 19, they were recognized in normal mucosa, adenoma, and carcinoma. These results suggested the intimate relationship between expression of CK subtypes, cellular differentiation, and structural differentiation of colorectal carcinoma.