Associations of matrix metalloproteinase-9 protein polymorphisms with lymph node metastasis but not invasion of gastric cancer

Purpose: Like most cancers, gastric cancer has a complex multistep etiology that involves both environmental and genetic factors. Matrix metalloproteinase-9 (MMP-9) is frequently over-expressed in gastric cancer. We investigated the effect of the genetic differences in MMP-9 coding region on the occurrence and progression of gastric cancer. Experimental Design: A case-control study was conducted in a population of 74 patients and 100 healthy people in southeast China. Individuals were genotyped for two single nucleotide polymorphisms (SNP) in MMP-9: R279Q and P574R. Genotypic distributions between patient and control groups were compared for correlations with cancer occurrence. Associations between genotypic distributions and several clinicopathologic features were also analyzed using univariate tests, multivariate logistic regression modeling, and stratified analyses. Results: Significant associations were revealed between both SNPs and lymph node metastasis [P = 0.012 and 0.025; odds ratio (OR), 3.4 and 2.8, respectively]. After adjustment using logistic regression for the potential confounding effects of gender, age, and location of the tumors, homozygous MMP-9 279RR and 574PP are more evidently associated with lymph node metastasis with ORadjusted of 5.7 [95% confidence interval (95% CI), 1.80-18.34] and 4.2 (95% CI, 1.37-12.69). The homozygous 279R-574P haplotype showed a stronger association by an ORadjusted of 6.1 (95% CI, 1.92-12.29) and was also associated with the 1-year postoperative mortality (ORadjusted, 6.5; 95% CI, 1.18-35.74). Interestingly, our data also suggested that the MMP-9 polymorphisms seem to result in higher risk of lymph node metastasis through a pathway independent of cancer invasion because no positive associations were found between these polymorphisms and cancer invasion (OR, 0.59 < 1). The stratified analyses indicated a synergistic interaction between the MMP-9 polymorphisms and the type of diffuse in affecting lymph node metastasis (OR, 13.4; P-between (strata) = 0.04). Significant association between both SNPs and the overall occurrence of gastric cancer was not observed. Conclusion:The present study has shown significant associations between the two nonsynonymous MMP-9 polymorphisms with lymph node metastasis in gastric cancer, especially with the diffuse type. The relatively large values of ORs and disassociation with cancer invasion suggest that the genetic differences of MMP-9 protein play an important and specific role in lymph node metastases, and therefore, further investigation of the underlying molecular mechanism is warranted.