Purpose: To test the multidrug resistance 1 (MDR1) gene expression in acute myeloid leukemia (AML) patients using the reverse transcription polymerase chain reaction (RT-PCR) in order to assess the application of the method for routine screening.
Materials and methods: 39 AML patients (mean age 43.9-/+18.2 years) and 10 healthy volunteers were studied by simultaneous amplification of the MDR1 and beta2-microglobulin (beta2-M) mRNA, as an internal control. Semi-quantitative characterization of MDR1 expression was done using a 4-grade scoring system: negative (-/+), weakly positive(-/+), moderately positive (+), strongly positive(++), according to the intensity of the MDR1 and beta2-M bands.
Results: The amplification of the MDR1 in healthy individuals yielded no products in 9 samples and in 1 case a (-/+) reaction was observed. In AML patients, RT-PCR revealed no MDR1 product (normal level) in 19 (48.7%) and (+)/(++) reaction (overexpression) in 15 (38.5%) patients. In the remaining 5 (12.8%) patients a (-/+) reaction was found, comparable to that of the (-/+) healthy individual (the level of MDR1 expression could not be defined). MDR1 overexpression was seen in 73.3% of the M1/M2 patients, and only in 14.3% of the M3 and M4/M5 patients. Besides, the MDR1(- )/(-/+)patients were significantly younger than MDR1(+)/ (++) patients (mean age 38.4-/+19.5/43.0-/+8.7 years, versus 51.1-/+16.7/65.0-/+4.3 years).
Conclusion: RT-PCR allows for the identification of patients with moderate and higher levels of MDR1 overexpression, while the weak positive reactions require additional testing. Besides, our data support the observation that the level of expression might be associated with the French-American-British (FAB) subtype of AML and with the age of the patients.