Isochaihulactone apparently induces G2/M phase arrest and changes the expression profiles of G2/M regulatory proteins. (A) Isochaihulactone induced cell cycle arrest at G2/M in LNCaP cells. For the cell cycle analysis, cells were seeded at 5 × 105 per 5-cm plate in triplicates and treated with 20 μM isochaihulactone for 12-48 h. The data represent the means ± S.D. from three different experiments. *, P < 0.05; **, P < 0.01; versus control. (B) Cells were treated with 20 μM isochaihulactone for 6-72 h. Western blot analysis of p53, p21, cdc25c, cyclin B1 and cdc2 was performed. β-actin was used as an internal control.