MMP12 and ovarian cancer: The remaining 12 studies with 12 polymorphisms [18, 20, 22, 23, 24] (12 polymorphisms including MMP2 C-1306T, MMP2 C-735T, MMP7 A-181G, MMP8 rs2155052, MMP8 rs11225395, MMP9 C-1562T, MMP9 rs6094237, MMP12 rs2276109, MMP13 rs17860523, MMP20 rs2292730, MMP20 rs12278250, MMP20 rs9787933) involving 2793 ovarian cancer cases and 3037 controls could not be quantitatively synthesized, thus the systematic review was performed.