A High-Content Small Molecule Screen Identifies Sensitivity of Glioblastoma Stem Cells to Inhibition of Polo-Like Kinase 1
Figure 6
Alternative Plk1 inhibitors in clinical development compare favourably with BI 2536 in selectivity against GNS cells and blood-brain barrier permeability.
(A) Co-culture of equal numbers of GFP-transfected G144 cell lines together with wild-type CB660 cells. In the presence of BI2536 GNS cells are selectively lost in the culture, while normal NS cells continue to proliferate. (B) DAPI staining of day 10 cultures of GNS or NS cells confirms that NS cells continue to undergo normal mitosis (anaphase events in red circles), without evidence of mitotic slippage and lagging chromosomes. (C) Two other Plk1 inhibitors in clinical development are selective against GNS cells (G7) compared to foetal NS cells (CB11130 and CB11171; chosen as they have a similar doubling time to G7). (D) Relative numbers of GNS cells arrested in mitosis after 48 h treatment with Plk1 inhibitors using an in vitro blood-brain barrier co-culture model. Inhibitors were added directly or via cell culture inserts containing a confluent layer of endothelial cells, and anti-mitotic responses were assessed in G7. J101 displayed poor blood-brain barrier permeability (P<0.001). GSK461364 performed similarly to BI 2536. Values shown are percentages of pHH3-positive cells relative to no-insert value of GSK 461364 treated GNS cells (n = 3). (E) Dose-response curves and IC50 values for specific Plk1 inhibitors BI 2536 and GSK 461363. NS and GNS cells were treated with different concentrations of the Plk1 inhibitors BI 2536 and GSK461364. Five days after treatment the total number of viable cells was counted and normalised to DMSO control values. Calculation of IC50 values confirmed the differential effect of both inhibitors on NS and GNS cells, with G7 being most sensitive.