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].
In Vitro
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].
Kinase Assay
Cell Assay
Cell Viability Assay on treated cells in 96-well plates, based on viable cells. 20 μL of CellTiter-Blue®reagent is added to each well and then incubated at 37°C with 5% CO2 for 4h before fluorescence reading using a Victor 1420 Multilabel Counter. All experiments are performed in triplicate and at least three independent experiments are performed. Data are presented as percentage compared with control.
Animal Administration
Viable MDA-MB-231 or HeLa cells (1×106) are resuspended in 300 μL of 0.9% NaCl and s.c. injected into both flanks of nude mice (MDA-MB-231: n=8 mice in each group, total N=16; HeLa: n=7 mice in each group, total N=14). Approximately 3 weeks after inoculation, mice are treated with Poloxin (40 mg/kg) or TQ (20 mg/kg) by intratumoral injection on Mondays, Wednesdays, and Fridays for 5 to 6 weeks. The tumor area is calculated by multiplication of the greatest diameter with the perpendicular diameter every 2 to 3 days. Measurements of all tumors within the group are represented by the mean value. U-tests and Student's t-tests are performed for statistical evaluation among MDA-MB-231 groups and between HeLa groups, respectively. All mice are properly treated in accordance with the guidelines of the local animal committee.
References
[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.
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