Anticancer effects of the PLK4 inhibitors CFI-400945 and centrinone in Ewing's sarcoma cells

Purpose: Polo-like kinase 4 (PLK4) inhibitors, such as CFI-400945 and centrinone, are emerging as promising antineoplastic agents. However, their effectiveness against Ewing's sarcoma, a highly aggressive childhood Cancer, remains to be established.

Methods: CFI-400945 and centrinone were tested in three Ewing's sarcoma cell lines with different TP53 status. Effects were assessed by flow-cytometric analyses of cell death, dissipation of the mitochondrial transmembrane potential and cell cycle distribution, by cell viability assay as well as by Caspase 3/7 activity measurement, by immunoblotting and by immunofluorescence microscopy.

Results: CFI-400945 and centrinone elicited cell death in p53 wild-type and mutant Ewing's sarcoma cells. Both agents induced mitochondrial membrane depolarisation, Caspase 3/7 activation, PARP1 cleavage and DNA fragmentation, indicating an apoptotic form of cell death. In addition, the PLK4 inhibitors induced a G2/M cell cycle arrest, particularly when cell killing was attenuated by the pan-caspase inhibitor z-VAD-fmk. Moreover, CFI-400945 treatment produced polyploidy.

Conclusion: Our findings show that PLK4 inhibitors were effective against Ewing's sarcoma cells in vitro and thus provide a rationale for their evaluation in vivo.