Epothilone A (Epo A) is a microtubule-stabilizing agent with EC0.01 of 2 μM.

Tubulin:2 μM(EC0.01)

Epothilone A诱导微管蛋白聚合, 导致细胞周期在G2-M期停滞, 具有细胞毒性,也诱导细胞凋亡。Epothilone A有效抑制HCT116细胞增殖,IC50为4.4 nM。Epothilone A 对KB3-1, KBV-1, Hela和 Hs578T细胞具有细胞毒性,IC50为13 nM到160 nM。Epothilone A与紫杉醇竞争性与微管结合,IC50为2.3 μM。

Tubulin polymerization assay: Samples for electron microscopy are placed on carbon-over-Parlodion-coated grids (300 mesh) and negatively stained with 2% uranyl acetate. Microtubule assembly in the presence or absence of Epothilone A is monitored spectrophotometrically by using a spectrophotometer equipped with a thermostatically regulated liquid circulator. The temperature is held at 35 °C and changes in turbidity (representative of polymer mass) are monitored at 350 nm. Effective concentration (EC0.01), defined as the interpolated concentration capable of inducing an initial slope of 0.01 OD/min rate, is calculated using the formula EC0.01 = concentration/slope.

Cell lines: KB3-1,KBV-1,Hela,and Hs578T cells. Concentrations: 0–2 μM. Method: cells are plated either in 48-well plates (for trypan blue and cell counting) or onto coverslips.After 24 hours,cells are treated with Epothilone A and are scored at regular intervals.For the cytotoxicity analysis,cells are counted and scored as trypan blue positive or negative.