Tumor targeting by doxorubicin-RGD-4C peptide conjugate in an orthotopic mouse hepatoma model

Vascular targeting is a novel strategy that directs endothelial toxins at tumor vessels expressing specific markers and kills tumor cells by vascular occlusion. Integrin-binding RGD motif has been reported to have a homing property to experimental tumor vasculature. In the present study, we evaluated the effect of vascular targeting by doxorubicin-RGD-4C conjugate in an orthotopic murine hepatoma model. MTT assay showed that dox-RGD-4C conjugates had lower cytotoxicity against MH134 mouse hepatoma cells than free dox. When given intravenously to mice with implanted orthotopic hepatoma, however, the dox-RGD-4C suppressed the growth of hepatoma more effectively than free dox (mean tumor volumes 24 mm(3) vs. 67 mm(3), respectively; p=0.047). Histologic analysis of the hepatoma tissue revealed prominent tumor cell death in the dox-RGD-4C treated group and complete tumor cell necrosis in 40% of cases. Immunochemical staining showed expression of integrin alphav mainly around the tumor nodule. These results show that dox-RGD-4C conjugate has a better antitumor effect in an orthotopic mouse hepatoma model by tumor targeting. Integrin alphav of hepatoma feeding vessels is suggested to be targeted by the dox-RGD-4C conjugate.