Chemical structure of pachymic acid (PA) and its effects on cell growth of human lung cancer cells. a Chemical structure of PA. b NCI-H23 and NCI-H460 cells were treated with 0, 20, 40, 80 and 160 µM PA for 24, 48 or 72 h, cell viability was measured by MTT assay. Absorbance was read at 490 nm with averages from triplicate wells. c, d NCI-H23 and NCI-H460 cells were treated with 0, 20, 40 and 80 μM PA for 24 h, the effect of PA on the growth of lung cancer cells was examined by colony formation assay (c) and EdU incorporation assay (d). Data are presented as mean ± SD from three independent experiments. *P < 0.05, **P < 0.01 compared with the control group.