Cell-specific alterations in glycoconjugates in the development of squamous metaplasia induced by benzo[a]pyrene in...

Squamous metaplasia of tracheal mucosa, putative preneoplastic lesions, involves replacement of normal mucociliary epithelium with epidermoid lesions. Alterations in cell differentiation and neoplasia accompany changes in glycoconjugates at the plasma membrane. Lectins which bind to specific cell surface glycoconjugates are used to elucidate such alterations. We have used peanut agglutinin (PNA) and concanavalin A (Con A) as specific molecular probes to elucidate cell specific alterations in the development and progression of squamous metaplasia in the hamster tracheal explants induced by benzo[a]pyrene (BP), a component of cigarette smoke. The tracheal explants were cultured in serum-free chemically defined medium and treated with BP (7.5 micrograms/ml) for up to 15 days. At this time, 80-90% of the carcinogen treated explants exhibited epidermoid lesions at various stages of development. The untreated control explants maintained normal pseudostratified epithelium. In these explants, PNA and Con A exhibited moderate reaction in the cytoplasm of luminal mucociliary cells; the basal cells showed no reaction. In early metaplastic lesions PNA and Con A stained only the cytoplasm of luminal cells; the metaplastic cells along the basal lamina were negative. In well-developed lesions, in which the luminal mucociliary layer was still intact overlying the lesions, the metaplastic epithelium remained unreactive with the lectins. In highly advanced lesions exhibiting cornification, and in which the mucociliary layer was sloughed, the metaplastic lesions showed strong reaction with both the lectins. The reaction was limited mainly to the plasma membrane of the metaplastic cells. These results show that induction and progression of the BP induced lesions accompany dynamic cell specific alterations in glycoconjugates. The epidermoid lesions acquire glycoconjugates rich in beta-D-galactose and D-mannose. These results are also consistent with the basal cell origin of the metaplastic lesions.