The instant invention provides methods and kits for inhibiting angiogenesis, tumor growth and metastasis, and endothelial cell interactions with the extracellular matrix, involving contacting the tumor or animal tissue with at least one isolated type IV collagen NC1 &agr; chain monomer. In a specific embodiment of the invention, the isolated domain of type IV collagen comprises the NC1 (&agr;1), (&agr;2), (&agr;3), or (&agr;6) chain monomer, or protein constructs having substantially the same structure as the NC1 (&agr;1), (&agr;2), (&agr;3), or (&agr;6) chain monomer.