Figure 6.

 Effect of Purvalanol A and Cdk4/6 Inhibitor IV on the sensitivity of Jurkat cells to methotrexate (MTX). (a) Whole‐cell extracts from Jurkat cells treated with the indicated concentrations of SU9516, Purvalanol A, Cdk4/6 Inhibitor IV, or dimethyl sulfoxide (DMSO) for 24 h were subjected to a Western blot analysis using dihydrofolate reductase (DHFR), phosphorylated pRB (Ser⁷⁸⁰), and GAPDH antibodies. (b) The cells were treated with DMSO or Purvalanol A (20 μM) for 24 h. Then the cells were cultured with the indicated concentrations of MTX, and subjected to a colony formation assay. The data are presented as a percentage compared to the control with PBS only, and the bars show SDs (*P < 0.05, **P < 0.01). (c) The cells were treated with DMSO or Cdk4/6 Inhibitor IV (20 μM) for 24 h. Then the cells were cultured with the indicated concentrations of MTX, and subjected to a colony formation assay. The data are presented as a percentage compared to the control with phosphate‐buffered saline (PBS) only, and the bars show SDs (*P < 0.05, **P < 0.01).