Figure 5

Cdk5 inhibition rescues p53 overexpressing cells from OA induced cell-death. (A) HTet23p53, HTet26p53, HTet43GFP and HeLa cells pretreated for 12 h with indicated concentrations of Cdk2/5 inhibitor or U0126 were treated with Dox in the presence or absence of OA and further incubated for 48 h before performing MTT assay to evaluate cell-survival. Bar graph represents variation within the wells of an experiment (± S.E.). *Represents P < 0.01. (B) HTet23p53, HTet26p53 and HTet43GFP cells plated in 96 well-plate were transfected with Ctrl or Cdk5 siRNA and incubated for 12 h. These cells were then transfected with PP2A siRNA and further incubated with Dox for 48 h. Cells were then processed for MTT assay. HTet23p53 cells were transfected with PP2A or Cdk5 siRNA and incubated with or without Dox for 48 h followed by western blotting for PP2A and p53 or Cdk5 respectively (upper panel). (C) Five hundred HTet23p53, HTet26p53 and HTet43GFP cells pretreated for 12 h with Cdk2/5 inhibitor, were treated with Dox and/or OA as mentioned in (A) and further incubated for 48 h. After 21 days cells were stained with crystal-violet and colonies were counted. Bar graph represents average colony number (± S.E.) form three independent experiments. *Represents P < 0.05. (D) HTet23p53, HTet26p53 and HeLa cells pretreated for 12 h with Cdk2/5 inhibitor followed by addition of Dox with or without OA were further incubated for 48 h and processed for apoptosis detection by TUNEL assay. Bar:10 μm.