title: Myeloid antigen co-expression in childhood acute lymphoblastic leukaemia: relationship with in vitro drug resistance.
abstract: Contradictory data have been reported about the prognostic value of myeloid antigen co-expression (My+) in childhood acute lymphoblastic leukaemia (ALL). In the present study the methyl thiazol tetrazoliumbromide (MTT) assay was used to compare the in vitro cytotoxicity of 14 drugs between 60 My+ (CD13+ and/or CD33+) and 107 My- ALL children at initial diagnosis. P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), major vault protein/lung resistance protein (LRP) and the intracellular daunorubicin concentration were studied by flow cytometry. My+ ALL samples were significantly more resistant, i.e. between 1.1- and 2.9-fold, to daunorubicin, doxorubicin, idarubicin, mitoxantrone, vincristine, 6-thioguanine, 6-mercaptopurine, teniposide, etoposide and ifosfamide compared with My- ALL samples. My- and My+ ALL did not significantly differ in sensitivity to prednisolone, dexamethasone, L-asparaginase and cytarabine. Comparable results were found when only common and preB ALL cases were analysed. Drug resistance in My+ ALL was not related to increased expression of P-gp, MRP or LRP compared with My- ALL (ratio My+/My-:P-gp 0.8, MRP 1.0, LRP 1.1). Accumulation and retention of daunorubicin did not significantly differ between My- and My+ ALL cells (ratio My+/My-: accumulation 1.2, retention 1.3). Therefore the nature of drug resistance in My+ ALL remains unknown. The lack of prognostic value for My+ in childhood ALL may be explained by the responsiveness of My+ ALL to glucocorticoids, L-asparaginase and cytarabine. In addition, the currently intensive treatment regimens may apply drug doses which are simply high enough to overcome the mild resistance to anthracyclines, mitoxantrone, vincristine, thiopurines, epipodophyllotoxins and ifosfamide in childhood My+ ALL.
authors.affiliation: Department of Paediatric Haematology/Oncology, University Hospital Vrije Universiteit, Amsterdam, The Netherlands. denboer@kgk.fgg.eur.nl
authors.forename: M L
authors.initials: ML
authors.lastname: Den Boer
authors.forename: P
authors.initials: P
authors.lastname: Kapaun
authors.forename: R
authors.initials: R
authors.lastname: Pieters
authors.forename: K M
authors.initials: KM
authors.lastname: Kazemier
authors.forename: G E
authors.initials: GE
authors.lastname: Janka-Schaub
authors.forename: A J
authors.initials: AJ
authors.lastname: Veerman
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000627:therapeutic use; D018826:CD13 Antigens / Q000378:metabolism; D003630:Daunorubicin / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy / Q000276:immunology*; D063268:Sialic Acid Binding Ig-like Lectin 3; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000970:Antineoplastic Agents; D018826:CD13 Antigens; D003630:Daunorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D063268:Sialic Acid Binding Ig-like Lectin 3; C571163:CD33 protein, human