Compositions and methods are provided for treating hemangiosarcoma in a subject. A recombinant AAV comprising a capsid and a vector genome comprising a nucleic acid expression cassette is provided. The expression cassette includes sequences encoding a promoter, a first signal peptide operably linked to an anti-VEGF antibody heavy chain immunoglobulin, a linker sequence, and a second signal peptide operably linked to an anti- VEGF light chain immunoglobulin, wherein said expression cassette co-expresses the immunoglobulin chains in a host cell under conditions which permit the chains to assemble into a functional anti-VEGF antibody. In one embodiment, the anti-VEGF antibody is a chimeric antibody.