title: Chemopreventive trials with vitamin A and beta-carotene: some unresolved issues.
abstract: The administration of beta-carotene (180 mg/week) plus vitamin A (100,000 IU/week) or vitamin A alone (200,000 IU/week) to chewers of betel quids in Kerala, India led to a reduction in the frequency of micronucleated buccal mucosal cells, a remission of oral leukoplakia, and an inhibition of the development of new leukoplakias. The advantages of this test system include a profound knowledge of exposure levels to tobacco-specific nitrosamines, areca nut-specific nitrosamines, and reactive oxygen species (ROS)-generating polyphenolics; the ease of quantitating micronuclei in exfoliated buccal mucosal cells and oral leukoplakia by noninvasive procedures; and solid information on the incidence of preneoplastic lesions and carcinomas. Some practical issues such as the level of nontoxic beta-carotene which could maintain the reduced frequency of micronucleated cells and the remission of oral leukoplakias for prolonged periods of time, the logistics of distributing beta-carotene to the many millions of smokeless tobacco users who are at elevated risk for oral cancer, and the possibility of using beta-carotene in the form of sweet potatoes or red palm oil, which could contain an economical source of beta-carotene for developing countries in which most of the tobacco chewers live, still remain unresolved.
authors.affiliation: Environmental Carcinogenesis Unit, British Columbia Cancer Research Centre, Vancouver, Canada.
authors.forename: H F
authors.initials: HF
authors.lastname: Stich
authors.forename: K D
authors.initials: KD
authors.lastname: Brunnemann
authors.forename: B
authors.initials: B
authors.lastname: Mathew
authors.forename: R
authors.initials: R
authors.lastname: Sankaranaryanan
authors.forename: M K
authors.initials: MK
authors.lastname: Nair
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D001114:Areca; D002338:Carotenoids / Q000008:administration & dosage; D006801:Humans; D007194:India; D007972:Leukoplakia, Oral / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D048629:Micronuclei, Chromosome-Defective / Q000032:analysis / Q000187:drug effects; D010946:Plants, Medicinal; D014801:Vitamin A / Q000008:administration & dosage; D019207:beta Carotene
chemical_list: D019207:beta Carotene; D014801:Vitamin A; D002338:Carotenoids