MMP7 and breast cancer: Genetically elevated serum MMP-7 level were not causally associated with risk of ER-negative BC (OR = 1.05, 95%CI: 0.97–1.14, P = 0.24), which was supported by the results of the other four datasets (ieu-a-1135: OR = 0.98, 95%CI: 0.89–1.07; P = 0.60; ieu-a-1136: OR = 1.10, 95% CI: 0.96–1.26, P = 0.19; ieu-a-1137: OR = 1.22, 95%CI: 0.99–1.50, P = 0.06; ieu-a-1166: OR = 1.08, 95%CI: 0.94–1.25, P = 0.28) (Table 3).