β-Carotene concentration in buccal mucosal cells with and without dysplastic oral leukoplakia after long-term β-carotene supplementation in male smokers

To measure the beta-carotene concentration in buccal mucosal cells in smoking men who had received long-term beta-carotene (BC) supplementation in a controlled trial. To assess the association of cellular BC on the prevalence of dysplasia in oral leukoplakia. An end-of-trial examination of a part of subjects in the Alpha-Tocopherol, Beta Carotene Cancer Prevention Study. 343 men who for 5-7 years had received BC (20 mg/d) or alpha-tocopherol (AT) (50 mg/d), or both of these or placebo. BC concentration of buccal mucosal cells was compared in the subjects with BC supplementation (n = 173) to that of those without it (n = 170). Oral mucosae were examined clinically and lesions showing leukoplakia histopathologically. Mean (s.d.) BC concentration in buccal mucosal cells was 7.7 (10.3)mg/kg protein in the subjects who received BC compared to 1.1 (1.7) mg/kg protein in those who did not. The BC concentration in the cells of supplemented subjects correlated with their serum BC levels (P < 0.001). AT supplementation had no effect on BC concentration nor was daily amount of smoking statistically significantly associated with the BC concentration in buccal cells. Altogether 17 subjects showed oral leukoplakia, 7 had dysplasia. In these 7 subjects, the BC concentration in buccal mucosal cells did not differ statistically significantly compared to subjects with only hyperkeratosis (n = 10) (F-test, P = 0.74). After long-term BC supplementation, BC concentration in oral mucosal cells was 7-fold greater than without supplementation. There was no evidence to support an association between cellular BC concentration and precancerous lesions among the few subjects having them in their oral mucosae.