The activity of matrix metalloproteinases (MMPs) is a universal feature of cellular invasion, tumor angiogenesis and metastasis,
which is counterbalanced and regulated by the natural tissue inhibitors of MMPs (Timps). Here we show that Timp1 gene transfer
delivered by an adeno-associated virus (AAV) vector inhibits tumor growth in a murine xenotransplant model. A human Kaposi’s
sarcoma cell line, forming highly vascularized tumors in vivo and having a high natural permissivity to AAV gene transfer, was
transduced to express the Timp1 cDNA. AAV-Timp1-transduced cells secreted high levels of Timp1 that inhibited MMP2 and
MMP9 gelatinolytic activity. Following subcutaneous inoculation in nude mice, the AAV-Timp1-transduced cells showed
significantly reduced tumor growth when compared to control AAV-LacZ-transduced cells. In addition, direct intratumoral injection
of AAV-Timp1 into pre-existing tumors significantly impaired the further expansion of the tumor mass. Histological analyses
showed that the AAV-Timp1-transduced tumors had limited development of vascular structures and extensive areas of cell death,
suggesting that Timp1 overexpression had an antiangiogenic effect. To further support this conclusion, we demonstrated that AAVTimp1
transduction significantly reduced endothelial cell migration and the invasion of a Matrigel barrier and strongly inhibited
angiogenesis in the chick chorioallantoic membrane assay. These results indicate that transfer and overexpression of the Timp1
gene is a promising therapeutic strategy to target tumor-associated angiogenesis in cancer gene therapy.
