In vitro effects of ??-carotene on human oral keratinocytes from precancerous lesions and squamous carcinoma:

Human keratinocytes, obtained from bioptic specimens of healthy and preneoplastic oral mucosa, and from human cell lines from oral cavity tumors (KB and SCC-25) were treated with beta-carotene (10-mu-M). The colony forming efficiency (CFE), the proliferation rate and the frequency of micronucleated cells were measured in these cultures. CFE was significantly reduced (p < 0.05) by beta-carotene treatment in cells from healthy mucosa and in KB cells. Decreases (p > 0.05; NS) were also observed in cells from pathological mucosa and in SCC-25 cells. Cell proliferation rate was not substantially affected by beta-carotene in all cultures. Finally, a decreased frequency of micronucleated cells was found in treated cultures, but significant reductions (p < 0.05) were only observed in cultures from oral mucosa (healthy and pathological) as well as in KB cell cultures. Our results indicate that beta-carotene is able to reduce the clonogenic activity (CFE), even if it does not seem to influence cell proliferation, and that it has a protective effect against genotoxic damage.