32/67-kD laminin receptor expression in human colonic neoplasia: Elevated transcript levels correlate with the degree of epithelial dysplasia

OBJECTIVE: The 32/67-kD laminin receptor is thought to be involved in tumor cell migration and metastasis formation, and enhanced expression was obser ved in human colorectal carcinoma. Our objective was to investigate further the expression of the 32/67-kD laminin receptor RNA in human colonic carci nogenesis. METHODS: We obtained sections of human colonic tissues in various stages of malignant transformation and analyzed them by in situ hybridization. RESULTS: Normal colonic mucosa displayed a gradient between crypt base and surface epithelium with lowest receptor RNA levels in superficial epithelia l cells. Increased laminin receptor RNA expression was observed in epitheli al cells of adenomas with positive correlation between transcript levels an d the degree of epithelial dysplasia. At variance with published results, w e did not observe significant differences in 32/67-kD laminin receptor tran scripts between adenomas with high-grade dysplasia and invasive adenocarcin oma. However, adenocarcinoma metastases displayed significantly higher lami nin receptor RNA levels than high-grade adenomas and primary carcinomas. CONCLUSIONS: We propose a two-step mechanism which controls first, upregula tion of laminin receptor RNA before the acquisition of an invasive phenotyp e in dysplastic epithelial cells, and second, a further upregulation in met astatic cells during the adenoma-carcinoma sequence of the colon. (C) 1999 by Am. Coll. of Gastroenterology.