Fig. 3. Low levels of CyclinB1 and CDK1 activity contribute to CHK1i resistance.

a Cells transfected with either control siRNA (siControl) or CCNB1 specific siRNA (siCCNB1) were harvested after 48 h and used for XTT growth assays against Prex (3, 6, and 12 nM) for an additional 48 h. b XTT growth assay on parental and PrexR cells after 48 h of cell culture against a gradient of the CDK1 inhibitor (CDK1i) Ro336 (0–10 µM) with or without Prex (20 nM). c PrexR cells were similarly treated as in (b). d Cell cycle analysis of parental cells treated with Ro336 (2.5 µM). All experiments were repeated at least thrice and representative figures are shown. Data are shown as mean ± SD. *P < 0.05; **P < 0.01; ***P < 0.001.