Figure 5.

Development of radioresistance is correlated with elevation of kinases involved in cell cycle progression and checkpoint control. Shown are the extracted-ion chromatograms for transitions monitored for the following peptides: (A) DIK*PENLLLDER (K* designates isotope-labeled desthiobiotin-conjugated lysine residue) from CHK1; (B) DLK*PQNLLIDDK from CDK1; and (C) DLK*PQNLLINTEGAIK from CDK2 in the LC–MRM experiments. (red) Light- and (blue) heavy- labeled peptides in (left) forward and (right) reverse labeling experiments. (D) Western blot analysis reveals the increased expression of CHK1, CDK1, and CDK2 in MCF-7/C6 relative to MCF-7/WT cells.