The contribution of cigarette consumption behavior to gastric cancer risk was 1.77- and 1.96-fold for those people without (95% CI = 0.774.08, P = 0.1770) or with 1G allele at MMP1 promoter -1607 (95% CI = 1.08-3.55, P = 0.0265) (Table 5). Here, MMP1 is linked to gastric cancer.