Determination of MDR1 gene expression in AML patients by quantitative RT-PCR analysis. RNA isolated from AML patients (AML1 and AML2) and a healthy individual (NPB) was reverse transcribed. Each cDNA was diluted, amplified by PCR with MDR1primer pairs (A) or β₂-microglobulin primer pairs (C), and subjected to autoradiography after 5% polyacrylamide gel electrophoresis and image analysis; values are plotted in graph (B and D, respectively).