Marked antitumor activity of cat's whiskers tea (Orthosiphon stamineus) extract in orthotopic model of human colon tumor in nude mice

Orthosiphon stamineus is used to treat kidney ailments including angiogenesis-dependent diseases. O. stamineus has shown to possess strong anti-angiogenic activity. In present study, an orthotopic nude mouse model of colon cancer was employed to study the factors that influence suppression of tumor by standardized 50% ethanol extract of O. stamineus leaves (EOS). Human colorectal cancer cells (HCT116) were surgically injected into the cecal wall of mice. Two different oral doses (100 and 200 mg/kg/day) were given for 5 weeks. EOS suppressed 61.62±3.7% and 82.8±1.5% tumor growth at 100 and 200 mg/kg, respectively. Tumor histology revealed significant reduction in vascularization. Anti-angiogenic efficacy of EOS was investigated in human endothelial cells (HUVEC). In vitro, EOS inhibited migration and tube formation of HUVECs. HPLC data showed high content of rosmarinic acid in EOS. This work supports previous anti-tumor works on the plant in which suppression of VEGFR phosphorylation is thought to be involved.