MMP9 and metastatic malignant neoplasm: Supporting this experimental strategy was that MAPK7 also has roles in metastatic cancer [28–33], so we would likely ‘hit’ several other genes/pathways as well as MMP9. We cloned highly metastatic human 143B cells with stably expressed short hairpin RNA (shRNA) to suppress MAPK7 (shMAPK7) (Fig. 4a, b), which had no impact on proliferation in vitro (Supplementary Fig. 2a).