Treatment of murine angiosarcoma with etoposide, TNP-470 and prednisolone.

To develop effective therapies for angiosarcoma, we investigated the anti-tumor effects of etoposide (ETO), TNP-470 and prednisolone (PSL) using an established murine angiosarcoma cell line (ISOS-1). We examined the direct anti-tumor and anti-angiogenic effects of these drugs on ISOS-1 cells and normal murine microvascular endothelial cells (mECs) in vitro. Cell growth of ISOS-1 was inhibited significantly by ETO, moderately by TNP-470, and not at all by PSL (IC(50): 0.25 microg/ml, 10 microg/ml, >8000 microg/ml, respectively). One the other hand, cell growth of mECs was inhibited significantly by TNP-470, slightly by PSL, and negligibly by ETO (IC(50): 0.85 ng/ml, 0.7 microg/ml, 10 microg/ml, respectively). In an in vivo assay, tumor growth of ISOS-1 was significantly inhibited by more than 2.5 mg/kg of ETO dose-dependently, and by more than 30 mg/kg of TNP-470, and 100 mg/kg of PSL individually. Combination treatments of ETO+TNP-470 and TNP-470+PSL showed synergistic enhancement of inhibition (% control inhibition: ETO vs. TNP-470 vs. ETO+TNP-470: 55 versus 55 vs. 16%) (% control inhibition: TNP-470 vs. PSL vs. TNP-470+PSL: 41 vs. 86 vs. 21%). ETO+PSL combination treatment, however, failed to show significant enhancement of anti-tumor effects. In conclusion, our results indicated that TNP-470 may be a very effective drug for angiosarcoma treatment, especially in combination with ETO or PSL. We eagerly anticipate the use of TNP-470 in clinical treatment of angiosarcoma.