The Clinical Significance of the Multidrug Resistance Proteins Expression in Patients with Acute Myeloid Leukemia.

Multidrug resistance (MDR), connected with the overexpression of several proteins e.g. MDR1, MDR3, MRP1, LRP and BCPR, has been implicated in refractoriness to chemotherapy in acute myeloid leukemia (AML). The aim of this study was to evaluate their clinical significance and individual contributions to the drug resistant phenotype in AML We studied 22 untreated patients with de novo AML, 12 F and 10 M (aged from 20 to 74 years, mean 48.2 yrs) between Jan. 2002 and June 2004. Acc. to FAB classification 2 cases were M0, 2 M1, 10 M2, 6 M4, 2 M5. We performed rhodamine 123 (Rho123) accumulation and retention test and, simultaneously, evaluated MDR1, MDR3, MRP1, LRP and BCPR proteins, in flow cytometry analysis using specific monoclonal antibodies, with leukemic blasts gated with leukemia cell-specific antibodies. In all patients the examination was performed twice: at diagnosis time and 2 days after the first course of chemotherapy (daunorubicine and cytosine arabinoside). The sample was classified as a positive when the mean geometric canal of fluorescence intensity (FI) was 1.5-fold higher than that of the negative (isotypic antibody) control.

12 out of 22 pts are alive, 7 had CR and 5 had NR. Out of 7 CR pts 4 had all tests negative, both at diagnosis and after chemotherapy, in 1 case the positive tests at diagnosis were reversed after chemotherapy, and in 2 the Rho123 test was positive at diagnosis and after chemotherapy. Out of 5 who had NR, 4 were positive in both, the Rho 123 test and MDR1 prior to chemotherapy and thereafter, and all 5 NR pts expressed LRP after chemotherapy. Ten out of 22 AML pts died, in four due to disease progression and six in the septic shock. Out of 4 who died in relapse 3 had positive the Rho123 test and elevated MDR1, both at diagnosis and after chemotherapy, and the remaining 1 became positive after chemotherapy. In 6 who died in the septic shock the Rho 123 test was negative and the multidrug resistance proteins not expressed. Overexpression of MDR1 was detected in 7/22 pts at diagnosis, and was reversed after chemotherapy in 1 case (CR) and all 6 positive remained were refractory to chemotherapy (2 died, and the other 4 had NR). MDR1 appeared after chemotherapy in 3 pts and all of them died. In 9 out of 15 who did not respond to chemotherapy MDR1 was elevated after chemotherapy and 15 of them died. In six out of 22 AML elevated LRP was found at diagnosis and after chemotherapy; 5 were resistant to chemotherapy (3 died, 2 had NR) and only 1 achieved CR. And all five LRP -negative at diagnosis and further LRP- positive after chemotherapy, did not achieve remission (3 died and 2 had NR). 10 out of 15 resistant pts overexpressed LPR after chemotherapy and 6 of them died. In 4 AML pts MRP was elevated at diagnosis, and 3 of them in whom it reversed after chemotherapy are alive (1 CR and 2 had NR) and 1 in whom MRP remained positive died. Out of 2 AML pts in whom MRP became overexpressed after chemotherapy 1 died and 1 had NR. Elevated BCPR was found at diagnosis in 2 AML pts, after chemotherapy it was reversed in one (CR) and in one remained expressed (NR); in remaining 3 pts BCPR appeared after chemotherapy (2 of them died).

We conclude, that the coexpression of several (at least two) multidrug resistance proteins is associated with an adverse prognosis and less CR.