Expression of c-myc in human colonic tissue in response to beta-carotene supplementation.
Dietary supplementation with beta-carotene at 30 mg/day results in an increased serum trans-retinoic acid concentration in patients with a prior colonic polyp. In a number of human cell lines, trans-retinoic acid upregulates c-myc mRNA expression in colonic mucosa by reverse transcription polymerase chain reaction and correlated the results with serum concentrations of all-trans- (ATRA), 13-cis-(13-cRA), and total retinoic acid. Serum and colonic biopsy samples were obtained before and 90 days after administration of a placebo (n = 7) or 30 mg of beta-carotene (n = 5) daily. An increase in c-myc expression after supplementation was observed in 6 of 12 subjects, but 5 of these 6 subjects had decreased total serum retinoic acid concentration and 4 had decreased ATRA concentration. In addition, five of the six subjects with increased c-myc expression had received a placebo. Conversely, c-myc expression was increased in only two of five paired samples from subjects whose total serum retinoic acid concentration increased during the 90-day supplementation period. We conclude that c-myc expression is not correlated with ATRA, 13-cRA, or total retinoic acid concentration in vivo and that increased serum retinoic acid secondary to increased tissue beta-carotene is not sufficient to activate c-myc transcription.
Gowda
B
B
Department of Medicine, Loyola University Medical Center, Maywood, IL 60153, USA.
Qin
J
J
Mobarhan
S
S
Frommel
T O
TO
D000368:Aged; D000369:Aged, 80 and over; D000975:Antioxidants / Q000008:administration & dosage* / Q000032:analysis / Q000378:metabolism; D001483:Base Sequence; D001706:Biopsy; D003106:Colon / Q000473:pathology*; D017931:DNA Primers / Q000737:chemistry; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009092:Mucous Membrane / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis* / Q000235:genetics; D014212:Tretinoin / Q000097:blood* / Q000145:classification / Q000378:metabolism; D019207:beta Carotene / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism
D000975:Antioxidants; D017931:DNA Primers; D012333:RNA, Messenger; D019207:beta Carotene; D014212:Tretinoin