Figure 3. Knockdown of HdmX enhances doxorubicin-induced cytotoxicity.. (A) Percent cell viability relative to untransfected untreated control cells. MCF7 cells were treated with doxorubicin (0.25-1.0 μg/mL) for 48 hours and cell viability was determined by absorbance at 590 nm. The loss of HdmX and/or Hdm2 showed an enhanced cytotoxicity relative to control cells. (B) RT-qPCR analysis of hdmX, hdm2, p21 and p53 gene expression in the indicated siRNA transfected MCF7 cells. The hdmX, hdm2, and p53 transcripts were effectively knocked down by siRNA prior to drug treatment.