AIM:To investigate the effect of the G-1666A polymorphism in the multidrug resistance related protein-1 (MRP1) on outcome of hepatocellular carcinoma (HCC). METHODS:A cohort of 162 patients with surgically resected HCC who received no postsurgical treatment until relapse was studied. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism analysis. Electrophoretic mobility shift assay (EMSA) was used to evaluate the influence of the G-1666A polymorphism on the binding affinity of the MRP1 promoter with its putative transcription factors. RESULTS:Kaplan-Meier analysis showed that patients with GG homologues had a reduced 4-year disease-free survival compared with those carrying at least one A allele (P = 0.011). Multivariate Cox regression analysis indicated that the-1666GG genotype represented an independent predictor of poorer disease-free survival [hazard ratio (HR) = 3.067,95% confidence interval (CI):1.587-5.952,P = 0.001],and this trend became worse in men (HR = 3.154,95% CI:1.604-6.201,P = 0.001). A similar association was also observed between 4-year overall survival and the polymorphism in men (HR = 3.342,95% CI:1.474-7.576,P = 0.004). Moreover,EMSA suggested that the G allele had a stronger binding affinity to nuclear proteins. CONCLUSION:The MRP1-1666GG genotype predicted a worse outcome and was an independent predictor of poor survival in patients with HCC from Southeast China. AIM: To investigate the effect of the G-1666A polymorphism in the multidrug resistance related protein-1 (MRP1) on outcome of hepatocellular carcinoma (HCC). METHODS: A cohort of 162 patients with surgically resected HCC who received no postsurgical treatment until relapse was studied. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism analysis. Electrophoretic mobility shift assay (EMSA) was used to evaluate the influence of the G-1666A polymorphism on the binding affinity of the MRP1 promoter with its putative transcription factors. RESULTS: Kaplan-Meier analysis showed that the patients with GG homologues had a reduced 4-year disease-free survival compared with those carrying at least one A allele (P = 0.011). Multivariate Cox regression analysis indicated that the-1666GG genotype represented an independent predictor of poorer disease-free survival [hazard ratio (HR) = 3.067, 95% confidence interval (CI): 1.587-5.952, P = 0.001] A similar association was also observed between 4-year overall survival and the polymorphism in men (HR = 3.342, 95% CI: 1.474- 7.576, P = 0.004). Moreover, EMSA suggested that the G allele had a stronger binding affinity to nuclear proteins. CONCLUSION: The MRP1-1666GG genotype predicted a worse outcome and was an independent predictor of poor survival in patients with HCC from Southeast China .