Background:

Poloxin is a non-ATP competitive Polo-like Kinase 1 (PLK1) inhibitor that targets the polo-box domain, with an IC50 of appr 4.8 μM.
Poloxin (25 μM) induces defects in centrosome integrity, spindle formation, and chromosome alignment in mitosis. Centrosomal fragmentation induced by Poloxin is partially rescued by Kiz T379E. Poloxin (25 μM) activates the mitotic checkpoint, induces apoptosis and inhibits proliferation of MDA-MB-231 cells[1]. Poloxin inhibits proliferation in both cell lines with a comparable efficiency through 72 h period[2]. Poloxin inhibits the polo-box domain (PBD) interaction with an apparent IC50 of ～4.8 μM. Poloxin exhibits a loose Plk1 PBD specificity with 4-10 times higher IC50 values for Plk2 and Plk3, and does not significantly inhibit other types of phosphopeptide-binding domains such as FHA, WW, and SH2 domains[3].
Poloxin (40 mg/kg) decreases the proliferation of MDA-MB-231 cells, and surpresses the growth of the tumor nude mice bearing established xenografts of MDA-MB-231[1].
Reference:
[1]. Yuan J, et al. Polo-box domain inhibitor poloxin activates the spindle assembly checkpoint and inhibits tumor growth in vivo. Am J Pathol. 2011 Oct;179(4):2091-9.
[2]. Sanhaji M, et al. p53 is not directly relevant to the response of Polo-like kinase 1 inhibitors. Cell Cycle. 2012 Feb 1;11(3):543-53.
[3]. Lee KS, et al. Pinning down the polo-box domain. Chem Biol. 2008 May;15(5):415-6.
[4]. Reindl W, et al. Inhibition of polo-like kinase 1 by blocking polo-box domain-dependent protein-protein interactions. Chem Biol. 2008 May;15(5):459-66.