Figure 1.

MDR1 mRNA expression in gastric cancer cell lines. The level of MDR1 mRNA expression was determined by RT-PCR, and normalized by that of mRNA β-actin, which was used as a control for RNA. The cDNA reverse-transcribed from the mRNA was amplified separately with each primer pair for MDR1 and β-actin genes. Aliquots of each PCR reaction mixture were separated on 7% polyacrylamide gel. The gel was dried and exposed on X-ray film overnight.