Low MDR1 and BAALC expression Identifies a New Subgroup of Adult Cytogenetically Normal Acute Myeloid Leukemia with a Favorable Outcome

Cytogenetically normal acute myeloid leukemia (AML) is a heterogeneous disease, in terms of genetic/molecular abnormalities resulting into marked differences in outcome. We demonstrated that MDR1, BAALC expression was of prognostic significance and high MDR1 expression correlated with a high BAALC expression (r=0.487, P<0.001) in cytogenetically normal AML in the prophase study then we hypothesized that MDR1 and BAALC expression together would better identify the patient's risk profile.

Pretreatment bone marrow samples from 92 cytogenetically normal AML patients were analyzed for MDR1 and BAALC mRNA expression by real-time reverse transcriptase polymerase chain reaction. Patients were divided into low MDR1 and BAALC expression group and combined group (high MDR1 and/or high BAALC expression) according to MDR1 and BAALC levels and were compared for clinical outcome.

73 cases of 92 cytogenetically normal AML patients got CR after the first block with a CR rate being 79.3%. However, 29 cases of the CR patients relapsed with the relapsed rate being 39.7%. In contrast, Patients with low expression of both MDR1 and BAALC had a higher CR rate (93.3%vs72.6%, P=0.021), lower relapse rate (7.1% vs. 42.5%, P=0.000), longer OS (50.3% vs 17.8%,P=0.001) than high MDR1 and/or high BAALC expression (combined group) in cytogenecally normal AML. Results showed no statistical difference in CR rate (93.3%vs85.7%, P=0.341),relapse rate (7.1% vs. 8.8%, P=0.000) and OS (50.3% vs 63.1%,P=0.431) for cytogenetically normal patients with both MDR1 and BAALC low expression comparing to those with low-risk cytogenetically abnormal.

The combined assessment of BAALC and MDR1 expression can improve treatment stratification in adult cytogenetically normal AML. Low expression of both MDR1 and BAALC identifies cytogenetically normal AML patients with a favorable long-term outcome.

No relevant conflicts of interest to declare.