The membrane-type 1 matrix metalloproteinase (MT1-MMP) has been reported to mediate the activation of pro-gelatinase A (proMMP-2), which is associated with tumor proliferation and metastasis. MT1-MMP can also digest extracellular matrix (ECM) such as interstitial collagens, gelatin, and proteoglycan and thus may play an important role in pathophysiological digestion of ECM. We studied the inhibitory effect of various hydroxamate MMP inhibitors, including known inhibitors such as BB-94, BB-2516, GM6001, and Ro31-9790, on a deletion mutant of MT1-MMP lacking the transmembrane domain (ΔMT1) to further characterize the enzyme and develop a selective inhibitor for MT1-MMP. The evaluation of the inhibitory activities of various hydroxamates reveals general structural profiles affecting selectivities toward MMPs. In particular, a longer side chain at the P1' position is preferable for the binding to MMP-2, -3, and -9 and MT1-MMP. For the P2' position, an α-branched alkyl group is critical for the binding toward ΔMT1, while the introduction of a bulky group at the α-position of hydroxamic acid seems to diminish the activity against ΔMT1. Summation of the data on the sensitivity of ΔMT1 to various hydroxamate inhibitors indicates that (1) the volume of the S1' subsite of ΔMT1 is similar to that of MMP-2, -3, and -9, which is bigger than that of MMP-1, and (2) the S1 and S2' subsites are narrower than those in other MMPs. On the basis of these results, the hydroxamates with a P1' phenylpropyl and P2' α-branched alkyl group were synthesized and evaluated for inhibitory activity. These inhibitors (1h,i) showed strong activity against ΔMT1 over MMP-1, but no selectivity between ΔMT1 and MMP-9. These results are explained using molecular modeling studies conducted on MT1-MMP.
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