The highly polymorphic HRAS1 variable number of tandem repeats (VNTR) has been described as an inherited predisposing factor in various human cancers. The aim of the present study was to evaluate the association between the presence of rare HRAS1 VNTR alleles and colorectal adenoma and cancer. A total of 165 Japanese patients underwent total colonoscopy with informed consent, and were divided into 2 groups: colorectal neoplastic and non-neoplastic patients. Two hundred and sixteen HRAS1 VNTR alleles from 108 colorectal neoplastic patients (67 adenomas and 41 cancers) and 114 alleles from 57 non-neoplastic patients were genotyped using PCR-based long-agarose gel electrophoresis assay of peripheral blood leukocyte DNA. Rare alleles were differentiated from 4 types of common allele (a1, a2, a3 and a4) by shifts in electrophoretic mobility. The prevalence of rare HRAS1 VNTR alleles was higher in colorectal neoplastic patients than in non-neoplastic patients (25.4% and 34.1% versus 8.8%). The adjusted odds ratio with at least one rare allele was 8.65 (95% confidence interval = 2.93 ? 25.53, P < 0.0001) in colorectal neoplastic patients. The presence of rare HRAS1 VNTR alleles could be a genetic predisposing factor for risk of colorectal neoplasm in Japanese people
