Rifampicin as an oral angiogenesis inhibitor targeting hepatic cancers

Angiogenesis is an important therapeutic target in cancer, and to fully exploit its therapeutic potential, combination chemotherapeutic/antiangiogenic regimens should be optimized and delivered earlier to more patients. Ideally, this could be done by a single potent oral agent with established safety. Rifampicin, a semisynthetic antibiotic derived from the rifamycins, is one of the most commonly used pharmaceutical compounds worldwide in the treatment of tuberculosis. Here, we present the effects of oral rifampicin on human cancer progression and its antiangiogenic properties, which were comparable to the angiogenesis inhibitor endostatin. Clinically, low-dose p.o. administration of rifampicin to six high-risk patients with hepatitis C virus-related liver cirrhosis resulted in a single occurrence of hepatocellular carcinoma during the follow-up period of 97.3 +/- 29.1 (mean +/- SD) months. Experimentally, rifampicin rapidly and markedly down-regulated the expression of a wide spectrum of angiogenesis-associated genes in growing human microvascular endothelial cells, thereby suppressing endothelial cell proliferation and migration. Rifampicin, at higher concentrations, also directly inhibited the growth of a variety of human cancer cells. P.o. administration of rifampicin significantly inhibited in vivo growth and metastases of subcutaneous human cancer xenografts. Thus, the potent antiangiogenic properties of oral rifampicin therapy were effective in suppressing cancer progression. It provides a promising new addition to antiangiogenic strategies for designing human cancer therapies. Considering the clinical pharmacokinetics of rifampicin, which enters the enterohepatic circulation and undergoes subsequent hepatic accumulation, it may be especially beneficial as an antitumor agent targeting hepatobiliary tumors.