Novel combretastatin A-4 derivative XN0502 induces cell cycle arrest and apoptosis in A549 cells

Combretastatin A-4 (CA-4) is a tubulin-binding compound currently in phase II trial as a tumor vascular-targeting agent. The present study evaluates the anti-tumor activities and establishes the mechanism of the action of 4-(4-methoxyphenyl)-5-(3,4,5-trimethoxyphenyl)-1H-pyrazol-3-amine(XN0502), a novel synthesized CA-4 analogue, in an effort towards finding the favorable therapeutics of CA-4 derivatives. XN0502 is characterized by its more potent anti-proliferative activities against non-small cell lung cancer A549 cells (IC(50): 1.8 +/- 0.6 microM), than that on the normal human liver HL-7702 cells (IC(50): 9.1 +/- 0.4 microM). Of note, using tubulin polymerization assay, western blot and immuofluorescence analyses, XN0502 was showed to inhibit microtubule assembly at both molecular and cellular levels in A549 cells. Further studies indicated that XN0502 induced time- and dose-dependent G2/M arrest, accompanying with the reduction of CDC2/p34 expression and the downregulation of CDK7. The protein level alteration and the nuclear translocation of cyclinB1 were observed, denoting the M phase arrest in XN0502-treated cells. Moreover, XN0502 caused caspase-mediated apoptosis, as indicated by the cleavage of PARP, the reduction of procaspase-3 and procaspase-9, and the down-regulation of XIAP. Taken together, the current study demonstrates that the novel CA-4 analogue XN0502 is a promising anti-cancer agent with potent G2/M arrest- and apoptotic-inducing activities via targeting tubulin deserving further research and development, and helps provide data for exploiting new CA-4 analogues.