ANTITUMOR-ACTIVITY OF TP3(ANTI-P80)-POKEWEED ANTIVIRAL PROTEIN IMMUNOTOXIN IN HAMSTER-CHEEK POUCH AND SEVERE COMBINED IMMUNODEFICIENT MOUSEXENOGRAFT MODELS OF HUMAN OSTEOSARCOMA

TP3-pokeweed antiviral protein (PAP) immunotoxin is directed against t he p80 antigen on osteosarcoma cells. Previous studies have demonstrat ed that TP3-PAP kills clonogenic human osteosarcoma cells in vitro and shows significant antitumor activity in a murine soft tissue sarcoma model (P. M. Anderson, et al., Cancer Res., 55: 1321-1327, 1995.) In t his study, we demonstrate that TP3-PAP elicits potent irt vivo antitum or activity in a hamster cheek pouch model of human osteosarcoma. Furt hermore, treatment with TP3-PAP at nontoxic dose levels significantly delayed the emergence and progression of leg tumors and markedly impro ved tumor-free survival in severe combined immunodeficient mice challe nged with OHS human osteosarcoma cells. Thus, TP3-PAP may be useful in the treatment of poor risk osteosarcoma.