MMP1 and neoplasm: Intriguingly, in many solid tumors, MMPs are produced by tumor stromal cells, rather than by tumor cells, including tumor-associated interstitial collagenase (MMP-1), stromelysin-1 (MMP-3), stromelysin-3 (MMP-11), and gelatinase A (MMP-2) [47,48,49,50].