Eight hundred sixty-three subjects with
atrophic gastritis were recruited to participate in an ongoing
chemoprevention trial in Nariño, Colombia. The participants were randomly assigned to intervention
therapies, which included treatment to eradicate Helicobacter pylori
infection followed by daily dietary supplementation with
antioxidant micronutrients in a 2 x 2 x 2 factorial design. A series of biopsies of gastric mucosa were obtained according to a specified protocol from designated locations in the stomach for each participant at baseline (before intervention
therapy) and at year three. A systematic sample of 160 participants was selected from each of the eight treatment combinations.
DNA was isolated from each of these biopsies (n = 320), and the first exon of KRAS was amplified using PCR. Mutations in the KRAS gene were detected using denaturing gradient gel electrophoresis and confirmed by sequence analysis. Of all baseline biopsies, 14.4% (23 of 160) contained KRAS mutations. Among those participants with
atrophic gastritis without
metaplasia, 19.4% (6 of 25) contained KRAS mutations, indicating that mutation of this important gene is likely an early event in the etiology of gastric
carcinoma. An important association was found between the presence of KRAS mutations in baseline biopsies and the progression of preneoplastic lesions. Only 14.6% (20 of 137) of participants without baseline KRAS mutations progressed from
atrophic gastritis to intestinal
metaplasia or from small intestinal
metaplasia to colonic
metaplasia; however, 39.1% (9 of 23) with baseline KRAS mutations progressed to a more advanced lesion after 3 years [univariate odds ratio (OR), 3.76 (P = 0.05); multivariate OR adjusted for treatment, 3.74 (P = 0.04)]. In addition, the specificity of the KRAS mutation predicted progression. For those participants with G-->T transversions at position 1 of
codon 12 (GGT-->TGT), 19.4% (5 of 17) progressed (univariate OR, 2.4); however, 60.0% (3 of 5) of participants with G-->A transitions at position 1 of
codon 12 (GGT-->AGT) progressed (univariate OR, 8.7; P = 0.004 using chi2 test).