Expression of ABCB5 gene in hematological malignances and its significance.

We examined ABCB5 gene expression using real-time polymerase chain reaction (PCR) in leukemia cells from 29 patients with acute lymphoblastic leukemia (ALL), 24 patients with chronic lymphocytic leukemia (CLL), 42 with acute myeloid leukemia (AML), 22 with chronic myeloid leukemia (CML), 17 with lymphoma and 10 with multiple myeloma (MM). It was confirmed that expression of the ABCB5 gene is highly increased in B-precursor ALL and French-American-British (FAB) M1 and M2 types of AML and lymphoma. The ABCB5 gene is expressed more highly in patients with relapsed or refractory disease than in patients with drug sensitive acute leukemia. Furthermore, there was an evident positive correlation between ABCB5 mRNA expression and MDR1 mRNA expression, but no correlation with MRP mRNA expression or BCRP mRNA expression. Quantification of the ABCB5 gene by real-time PCR offers particular promise as a prognostic marker and a marker for drug resistance in acute leukemia. Our findings raise the possibility that ABCB5 may be responsible for both the progression and chemotherapeutic refractoriness of advanced acute leukemia, and that ABCB5-targeted approaches might therefore represent novel and translationally relevant therapeutic strategies for drug resistance in leukemia.