Growth inhibition of LNCaP cells induced by isochaihulactone is partially rescued by JNK1/2 inhibitor. (A) MTT assay of LNCaP cells pretreated with p38 inhibitor SB203580 (10 or 20 μM), the JNK1/2 inhibitor SP600125 (10 or 20 μM) or the ERK1/2 inhibitor PD98059 (25 or 50 μM) for 1 h and then treated with 20 μM of isochaihulactone for 48 h. The values are the mean ± S.D. from three independent experiments performed in duplicate. (B) Cells were treated with 20 μM isochaihulactone for the indicated times. Phospho-ERK1/2, total-ERK1/2, phospho-JNK, total-JNK, phospho-38, total-p38 were detected by western blotting. (C) Cells were treated with 20 μM isochaihulactone for 48 h in the presence or absence of JNK1/2 inhibitor SP600125 (20 μM). Cell cycle analysis was done as described in Methods. Isochaihulactone-induced sub-G1 population (20.51%) was decreased by JNK1/2 inhibitor SP600125 pre-treatment (7.54%). The data represent the means ± S.D. from three independent experiments. **, P <0.01; ***, P < 0.001 versus vehicle.