Read in the literature that TIMP-1 (tissue inhibitor of matrix metalloproteinase-1) is typically associated with inhibition of matrix metalloproteinases (MMP)-induced tumor cell invasion through the ECM. However, TIMP-1 is overexpressed in many malignancies and is associated with poor prognosis in breast cancer. To investigate the role of TIMP-1 in tumor cell invasion, you perform invasion assays using breast cancer cells that express normal levels of TIMP-1 and cells that overexpress TIMP-1, and you find that the overexpressing cells do not invade through Matrigel while the normal cells do. You then inject mice with either normal or overexpressing cells, and you find that the cells that overexpress TIMP-1 induced tumor growth and invasion while the normal expressers did not. What would you infer based on the data from this experiment?