MMP9 and cancer: Using the potent CDK7/9 inhibitor—SNS-032, it was demonstrated that pS2/5/7 at RNAP II, by these two kinases, could be inhibited in a dose-dependent manner, resulting in reduced cell proliferation, migration, invasion, cancer stemness, in vivo tumor formation, increased MMP-9, but not MMP-2, expression, in dose- and time-dependent manners.