Based on the discovery that a soluble polypeptide including a nonphosphorylatable form of the MT1-MMP cytoplasmic domain is capable of inhibiting MT1-MMP in a dominant negative manner, the present invention provides compositions including MT1-MMP inhibitors such as peptide inhibitors, and methods for treating diseases associated with MT1-MMP activity. Such diseases include cancer, arthritis, and heart disease, and vascular disease.