Quantitative mRNA Expression levels of Mdm2. Saos2 cells were transiently transfected with the indicated expression constructs. Mdm2 mRNA expression levels were determined by TaqMan RT-PCR as described in Materials and Methods. As internal reference, mRNA expression of GAPDH mRNA was used. Relative Mdm2 mRNA expression is shown and Mdm2 mRNA expression of vector transfected cells was set to 1. Bars, SD.