OBJECTIVETo explore the relationship of polymorphisms in the xeroderma pigmentosum group D (XPD) gene and the glutathione-S transferees M1 (GSTM1) gene with susceptibility to primary hepatic carcinoma (PHC) in Tibetans from the Qinghai region.

METHODSThis case-control study compared equal groups (n=102 each) of patients with PHC and healthy individuals recruited from Qinghai, Tibet.PCR and denaturing high-performance liquid chromatography (DHPLC) was used to detect each participant's genotypes for the XPD and GSTM1 genes.Non-conditional logistic regression modeling was used in multivariate analysis to evaluate the predictive value for PHC, to compare the risk of different genotypes for PHC, and to assess the risk of gene polymorphisms and environmental factors for PHC.

RESULTSSix factors, including smoking, carnivorous diet, alcohol consumption, hepatitis B virus (HBV) infection, immediate family members with HBV infection and immediate family members with history of PHC, were included in the logistic regression model (alpha =0.05).The XPD751C mutation genotype distribution frequencies were significantly higher in the cases than in the controls (21.6% vs. 10.8%, P=0.036). The risk of PHC increased 2.275 times (95% CI, 1.04-4.98). The frequencies of the GSTM1 genotype were remarkably higher in the cases than in the controls (60.4% vs. 39.6%, P=0.017), suggesting this as an exposure factor. Individuals with the GSTM1 genotype had 1.963 times higher risk of PHC than individuals without the GSTM1 genotype (95% CI, 1.124-3.428). With both the XPD751C mutation and the GSTM1 genotype as exposure factors, the risk incidence increased to 3.030 times (95% CI, 1.165-7.881), indicating that the combined genotypes have a synergistic effect.Application of unconditioned logistic stepwise regression analysis of the genotypes and environmental risk factors showed an interaction between the XPD751C mutation and HBV infection, alcohol consumption and immediate family members with history of PHC. In addition, an interaction between the GSTM1 genotype and HBV infection was found.

CONCLUSIONAlcohol consumption, HBV infection and the presence of immediate family members with HBV infection are the main environmental risk factors of PHC in Qinghai Tibetans.Qinghai Tibetans who carry the XPD751C gene mutation and the GSTM 1 genotype are at increased risk of PHC, compared to individuals carrying only one or the other.The XPD751C mutation may increase risk of PHC when combined with the environmental factors.