MMP1 and breast cancer: MMP1 overexpression was associated with worse OS in ER-positive BC patients (HR = 1.61; 95% CI: 1.24 - 2.09, p = 0.00027), but not associated with OS of ER-negative patients (HR = 1.1; 95% CI: 0.75 - 1.63, p = 0.62).