Next, to further probe the ability of the V66 antibody to cross the blood-brain barrier (BBB) and selectively target brain tumors in the context of the autochthonous Brca2-/-; Trp53-/- tumors, tumor-bearing mice were injected with fluorescently labeled V66 antibody compared with tumor-bearing mice injected with PBS and with non-tumor-bearing mice injected with labeled V66 (to establish background signal in healthy brain tissue). The gene discussed is BRCA2; the disease is brain neoplasm.