Although this association between an MMP inhibitor and poor cancer prognosis may be paradoxical, we describe here that while TIMP-2 regulation of MT1-MMP activity is complex, as exemplified by MDA-MB 231 and HS578t cells, high TIMP-2:low MT1-MMP ratios in these cells correlate with their migratory potential, and also with their lack of gelatin degradation and inhibited proMMP activation ability. This evidence concerns the gene TIMP2 and cancer.