TNP-470 inhibits collateralization to complement the anti-tumour effect of hepatic artery ligation

We examined hepatic artery ligation combined with an angiogenesis inhibitor, TNP-470, in the treatment of VX2 tumour inoculated into the liver of rabbits. Effects on tumour growth were correlated with arterial collateral development in this system. Three treatment methods were compared: (1) the left hepatic artery was ligated at the liver hilum (ligation group); (2) TNP-470 (40 mg per body) was infused continuously for 7 days via the common hepatic artery (TNP group); (3) the left hepatic artery was ligated and TNP-470 was infused continuously for 7 days via the common hepatic artery (ligation + TNP group). These treatments were started 12-14 days after tumour inoculation. The day of initiating treatment was defined as day 0. Although there were no significant differences in tumour volume among the three treated groups on day 7 after treatment, tumour volumes in the ligation + TNP group were significantly smaller than in the ligation group and the TNP group on day 14 after treatment. The vasculature and arterial collaterals around the tumour were demonstrated by the perfusion of a silicon rubber solution, Microfil. In the ligation + TNP group, the new microvasculature around the tumour decreased compared with the ligation group. The TNP-470 inhibition of microvascular proliferation may limit the development of collaterals that communicate with new feeding arteries. These results suggest that transarterial embolization combined with TNP-470 may enhance the anti-tumour effect of transarterial embolization alone in the treatment of liver tumours.