Immunohistochemical localization of integrins and basement membrane components in colorectal epithelial tumors correlates with their histologic architecture.

We studied the immunohistochemical localization of integrins (alpha2, alpha6) and basement membrane components (type IV collagen, laminin) in colorectal epithelial tumors (adenomas and adenocarcinomas) with respect to their intramucosal and invasive growth. The integrins showed two patterns of localization: basal polarization and diffuse expression. In intramucosal tumors, the basement membrane components were well preserved, and the staining intensity for the basal polarization of alpha6 increased with increasing size and grade of dysplasia of the tumors. In invasive adenocarcinomas, the basement membrane components were preserved, and the basal polarization of alpha6 was apparent in well-differentiated areas, while the tumor cells showed disorganization or loss of the basement membrane components and the diffuse expression of alpha6 with a reduction or loss of the basal polarization in moderately and poorly differentiated areas. The expression of alpha2 did not correlate with the grade of dysplasia of intramucosal tumors or the pattern of differentiation of invasive adenocarcinomas. These results suggest that the basal polarization of alpha6 and the preservation of the basement membrane components contribute to the glandular architecture of colorectal epithelial tumors, and that the diffuse expression of alpha6 with a reduction or loss of the basal polarization, and the disorganization and loss of the basement membrane components to the dispolarized affinity of tumor cells to the extracellular matrix.