Key Words Gastric cancer • PTPN11 • SNP • Chemotherapy •Prognosis • Gene-environment interaction Objective: Since gastric cancer (GC) cells exhibited higher grades of SHP-2 encoded by PTPN11 than normal cells, it would be intriguing to explore whether PTPN11 single nucleotide a Chinese population. Methods: Altogether 430 late-stage GC patients and 960 healthy controls matched with age and sex were incorporated. Three PTPN11 SNPs (i.e. rs7958372, rs12229892 and rs2301756) were genotyped by

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... rase chain reaction-restriction fragment length regression. Survival curves were plotted with Kaplan-Meier method and the COX proportional hazard model was used to analyze independent factors for GC prognosis. Results: For rs12229892, AA and GA genotypes would cause 1.60-fold increase of GC risk in comparison to homozygote GG (OR = 1.60; 95% CI = 1.23-2.07; P < 0.001). The A allele of rs2301756 was = 0.81; 95% CI = 0.65-0.99; P = 0.043). Results from both 2-cycle and 4-cycle chemotherapy rs2301756 compared with homozygote GG (P < 0.001). Besides, the joint impact of rs12229892 (AA) and environmental factors (i.e. smoking, family history, intake of processed food and H .pylori infection) on GC risk was considered as positive interaction, while that of rs2301756 (AA) and the above parameters was deemed as negative interaction. Finally, differentiation degree, axillary lymph node metastasis, rs12229892 and rs2301756 appeared as independent risk factors for GC development (all P < 0.05). Conclusion: Since rs2301756 polymorphism of PTPN11 was associated with reduced risk of GC and better effects of chemotherapy on GC, it can be considered as a predictor of GC prognosis and the treatment target for GC.