Effects of 7a on the microtubule assembly in vivo and in vitro. (A) Hep3B cells were treated with vehicle (DMSO, as CTL), 1 μM 7a, 1 μM vinblastine, 1 μM vincristine, 1 μM colchicine, or 1 μM paclitaxel for 24 h. Cytosolic (S, soluble) and cytoskeletal (P, polymerized tubulin) fractions were separated and followed by western blot analysis to detect α-tubulin, β-tubulin and β-actin protein expression. (B) GPEM buffer containing pure tubulin protein was incubated with vehicle (DMSO, as control) or 0.3, 1, 3, 10 μM 7a, 10 μM vinblastine, 10 μM vincristine, 10 μM colchicine, or 10 μM paclitaxel at 37 °C. Signals from compound-effected tubulin polymerization were recorded kinetically by microplate reader at the absorbance of 340 nm.