Different requirements for the chromosomal passenger complex to maintain a mitotic checkpoint arrest induced by different spindle poisons. Example of an experiment in which osteosarcoma cells (U2OS) were transfected with mock shRNA, Mad2 shRNA, or shRNA for INCENP (which results in knock-down of all chromosomal passenger complex components). Transfected cells were released from a 24 h thymidine block into the indicated drugs. Eighteen hours after the release cells were fixed and prepared for FACS analysis. The MPM2 antibody was used to determine the mitotic index. This type of experiment shows that knock-down of a classical checkpoint protein (Mad2) does not allow cells to accumulate in mitosis with any of the drugs, while knock-down of the chromosomal passenger complex affects the response to paclitaxel and monastrol more dramatically than the response to nocodazole.