Figure 1.

 The knockdown of dihydrofolate reductase (DHFR) expression enhanced sensitivity to methotrexate (MTX) in Jurkat cells. (a) Jurkat cells were transfected with DHFR siRNA or negative control siRNA by electroporation. After 48 h, cells were subjected to a Western blot analysis using DHFR and β‐actin antibodies to verify the reduction in DHFR expression by siRNA. (b) Transfected cells were cultured with the indicated concentrations of MTX and subjected to colony formation assays. The data are presented as a percentage compared to the control with an equivalent amount of PBS, and the bars show SDs (*P < 0.05, **P < 0.01). PBS, phosphate‐buffered saline.