Proteolytic inactivation of the autoinhibitory prodomain is essential for the pro-tumorigenic function of membrane type-1 matrix metalloproteinase (MT1-MMP)

Invasive cancers employ pericellular proteolysis to breach the extracellular matrix and basement membrane barriers and invade the surrounding tissue. Pro-invasive, pro-tumorigenic MT1-MMP is the primary mediator of proteolytic events on the cancer cell surface. Cellular MT1-MMP is synthesized as a latent zymogen. The latency of MT1-MMP is maintained by its N-terminal inhibitory prodomain. Our study reveals a critical mechanism underlying the activation pathway and subsequent execution of the tumor-promoting function of MT1-MMP. Evidence suggests that the prodomain undergoes intradomain cleavage at the PGD↓L50 cleavage site followed by the release of the degraded prodomain by furin cleavage of the R108RKR111↓Y112 site. These events, only if combined, cause the activation of MT1-MMP. The significance of these molecular events to the pro-tumorigenic function of MT1-MMP in malignancy remained, however, unidentified. To identify the functional importance of the PGD↓L50 intradomain cleavage in the activation and tumorigenic program of MT1-MMP, our current studies employed the cells which expressed the wild-type prodomain-based fluorescent biosensor and the mutant biosensor with the inactivated PGD↓L50 cleavage site (L50D mutant) and also the cells with the enforced expression the wild-type and mutant MT1-MMP. Using cell-based tests and orthotopic breast cancer xenografts in mice, we demonstrated that the intradomain cleavage of the PGD↓L50 sequence of the prodomain is essential for the pro-tumorigenic function of MT1-MMP. Our study contributes to the growing consensus for the design of selective, precisely focused MT1-MMP inhibitors in cancer. Analysis of global gene expression in orthotopic tumor and cultured breast cancer cells expressing wild-type and mutant Mt1-MMP forms