Abstract C195: Inhibition of polo-like kinase 1 (PLK1) by BI 2536: Effects on mitotic index, clonogenic capacity, and proliferation in medulloblastoma cell lines.

Abstract

Abstract Medulloblastoma is the most common central nervous system tumor in childhood. Despite high survival rates (over 50% for most protocols) the treatment for this tumor usually results in severe sequels. Still, in patients younger than 3 years-old radiotherapy cannot be used turning the prognosis even worse. Polo-like kinase 1 (PLK1), a serine-threonine kinase that regulates mitosis progression, has been repeatedly associated with increased cell proliferation and poorer prognosis in several types of cancer. The aim of this study was to evaluate the effects of the inhibition of PLK1 with BI 2536 on mitotic index clonogenic capacity and cell proliferation, on the UW402 and UW473 pediatric medulloblastoma cell lines. Equal numbers of cells were treated with 50, 100 and 150 nM of BI 2536 for 24, 48 and 72 hours. To calculate the mitotic index cells after treatment dropped onto glass slides, allowed to air dry and stained with Giemsa, 1000 cells were counted. To calculated the clonogenic capacity cells were treated, let to grow for 7 days and then the colonies were fixed with methanol and stained with Giemsa. Only colonies with > 50 cells were counted. To analyze the proliferation cells after treatment were let with culture medium containing 10 μL of XTT dye (XTT II; Roche Molecular Biochemicals, Indianapolis, IN), plates were incubated for 2 hours at 37°C and the formazan product was measured at 450 nm by using an iMark microplate reader (Bio-Rad Laboratories). Each experiment was performed in triplicate wells and repeated in three sets of tests. The tests were analyzed by oneway ANOVA followed by Home-Sidak test. Values of p≤0.05 were considered statistically significant. The Inhibition of PLK1 by this drug showed an efficient decrease (p<0.05) on cell proliferation in dose- and time-dependent manner. The clonogenic assay also demonstrated that BI 2536 causes a significant reduction in colony formation at concentrations as low as 5nM (p<0.05). The mitotic index analysis showed a significant accumulation of dividing cells (p<0.05) with a more evident effect after 24h of treatment. Although further studies are needed, our results point to PLK1 as a potential target to improve medulloblastoma treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C195.