Combretastatin A1 is a cis-stilbene originally isolated from C. caffrum that inhibits microtubule assembly (ID50 = 2 µM) by binding to the colchicine binding site on β-tubulin. It inhibits proliferation of hepatocellular carcinoma (IC50s = 9.2-728.2 nM) and other carcinoma cell lines (IC50s = 12.2-2,247 nM). Combretastatin A1 increases apoptosis of HepG2 cells in a GSK3β-dependent manner by decreasing the levels of MCL-1 and β-catenin. It inhibits tumor growth in a hepatocellular carcinoma mouse xenograft model when administered at doses of 2 or 4 mg/kg for 4 weeks. It also enhances the effects of carboplatin , paclitaxel , and cisplatin in murine models of cancer. Combretastatin A1 decreases functional vascular volume within hours in a well-vascularized murine colon adenocarcinoma model.