Altered cytokeratin expression in carcinogenesis inhibition by antioxidant nutrients

Abstract

Epidermoid carcinomas were induced in hamster buccal pouches with use of 7,12 dimethyl‐benz[a]anthracene (DMBA). In five animals that served as tumor controls (Group 1), right buccal pouches were painted with DMBA (0.5% solution in mineral oil) thrice weekly for 14 weeks. In five animals (Group 2), right buccal pouches were painted with DMBA and reduced glutathione (GSH) was administered systemically by mouth. Five animals (Group 3) received vitamin E instead of glutathione. An additional 20 animals (Groups 4, 5, 6, and 7) were untreated, vehicle, glutathione, and vitamin E controls, respectively. Glutathione and vitamin E were given in doses of 10 mg/kg in 0.5 ml of mineral oil thrice weekly on days alternate to DMBA painting. Treatment by GSH and vitamin E reduced the number and size of tumors that were formed. Histopathologically, there were also fewer sites of dysplasia, carcinoma in situ, and early invasive epidermoid carcinoma than in the tumor control animals. The formalin‐fixed and paraffin‐embedded buccal pouch sections were stained immunohistochemically with use of monoclonal antibodies for cytokeratins. These included high‐molecular‐weight keratins (50,000–68,000 mol wt) 10, 13, and 8 (k10, k13, and k8, respectively). Oral carcinomas and dysplastic sites exhibited basal and suprabasal (spinous layer) high levels of k10, k13, and k8 staining. Treatment with GSH or vitamin E increased the suprabasal staining for high‐molecular‐weight keratins and reduced the protein expression for klO, k10, or k8. This pattern of staining was observed in dysplastic as well as in carcinoma sites. These results indicate that cytokeratin protein expression could contribute to a common biomarker analysis for chemoprevention.