Fig. 5: Chk2 deficiency sensitizes cells to PLK1 inhibition.

A Top, experimental setup. Bottom, relative cell viability (DMSO = 1) measured by crystal violet following 3-day treatment with PLK1 inhibitor BI-2536. Points represent average of N = 4 experimental replicate values averaged from technical triplicates. Error bars SEM of replicate averages. B Representative blots of cells treated for 3 days with either a nontargeting siRNA (control) or siRNA against Chk2 in Hela, U2OS, and A549 cells. C Quantification of cell viability following siRNA treatment and 2.27 nM BI-2536. Each point marks the mean of N = 3 HeLa, N = 4 U2OS and A549 experimental replicates, each averages from technical triplicates and normalized to DMSO-treated cells. Error bars SD of experimental replicates. p = 0.049 HeLa, p = 0.065 U2OS, p = 0.0176 A549 ratio paired two-tailed t-test of replicate mean values. D Map of Chk2 protein with indicated domains including S/T-Q cluster, FHA2, kinase, and nuclear localization sequence (NLS). Top, trace file of Chek2 locus from HCT-116 cells. Gray shading indicates the heterozygous L355P mutation. E Top, experimental setup. Bottom, representative western blot of HCT-116 cells with or without Chk2-mCherry challenged with etoposide (Etop, 10 μM) or in combination with Chk2i (10 μM BML-277) for 6 h. Numbers are quantification of p-Y15 signal normalized to GAPDH loading control and to DMSO-treated condition. This experiment has been repeated 1 other time with similar results. F Left, quantification of p-TCTP abundance in STLC-arrested HCT-116 cells transduced with a doxycycline (DOX)-inducible 3xFLAG-Chk2 construct. Cells were either treated with 0.1 μM DOX or untreated for 48 h prior to STLC addition. Each point represents one cell normalized to the average value in the untreated condition for each replicate. Error bars SD of individual cell values combined from N = 3 experimental replicates, n = 131 -DOX, n = 141 + DOX. *p < 0.05, two-tailed t-test of replicate mean values. Right, representative immunofluorescence image. Scale bar, 5 μm. G Representative western blot of HCT-116 cells with or without expression of the Chk2-mCherry rescue construct. H Quantification of relative cell viability in HCT-116 cells following 3-day treatment with BI-2536 titration. Points represent average of 3–4 experimental replicate values averaged from technical triplicates. Error bars SEM of replicate averages. Source data are provided as a Source Data file.