MMP3 and breast cancer: Genetically elevated serum MMP-3 level were not causally associated with risk of ER-negative BC (OR = 1.01, 95%CI: 0.93–1.09, P = 0.88), which was supported by the results of the other four datasets (ieu-a-1135: OR = 0.99, 95%CI: 0.91–1.08; P = 0.88; ieu-a-1136: OR = 0.99, 95% CI: 0.86–1.14, P = 0.884; ieu-a-1137: OR = 1.08, 95%CI: 0.97–1.20, P = 0.17; ieu-a-1166: OR = 1.00, 95%CI: 0.89–1.12, P = 1.00)(Table 2).