title: P-gp activity is a critical resistance factor against AVE9633 and DM4 cytotoxicity in leukaemia cell lines, but not a major mechanism of chemoresistance in cells from acute myeloid leukaemia patients.
abstract: BACKGROUND
  AVE9633 is a new immunoconjugate comprising a humanized monoclonal antibody, anti-CD33 antigen, linked through a disulfide bond to the maytansine derivative DM4, a cytotoxic agent and potent tubulin inhibitor. It is undergoing a phase I clinical trial. Chemoresistance to anti-mitotic agents has been shown to be related, in part, to overexpression of ABC proteins. The aim of the present study was to investigate the potential roles of P-gp, MRP1 and BCRP in cytotoxicity in AVE9633-induced acute myeloid leukaemia (AML).
  
  
  METHODS
  This study used AML cell lines expressing different levels of P-gp, MRP1 or BCRP proteins and twenty-five samples from AML patients. Expression and functionality of the transporter protein were analyzed by flow cytometry. The cytotoxicity of the drug was evaluated by MTT and apoptosis assays.
  
  
  RESULTS
  P-gp activity, but not MRP1 and BCRP, attenuated AVE9633 and DM4 cytotoxicity in myeloid cell lines. Zosuquidar, a potent specific P-gp inhibitor, restored the sensitivity of cells expressing P-gp to both AVE9633 and DM4. However, the data from AML patients show that 10/25 samples of AML cells (40%) were resistant to AVE9633 or DM4 (IC(50) > 500 nM), and this was not related to P-gp activity (p-Value: 0.7). Zosuquidar also failed to re-establish drug sensitivity. Furthermore, this resistance was not correlated with CD33 expression (p-Value: 0.6) in those cells.
  
  
  CONCLUSIONS
  P-gp activity is not a crucial mechanism of chemoresistance to AVE9633. For patients whose resistance to conventional anthracycline AML regimens is related to ABC protein expression, a combination with AVE9633 could be beneficial. Other mechanisms such as microtubule alteration could play an important role in chemoresistance to AVE9633.
authors: Assistance Publique Hôpitaux de Paris, Hôpital Hôtel Dieu, 1 Place du Parvis de Notre-Dame, Paris Cedex 04, France. ruoping.tang@htd.aphp.fr
authors: Ruoping
authors: R
authors: Tang
authors: Simy
authors: S
authors: Cohen
authors: Jean-Yves
authors: JY
authors: Perrot
authors: Anne-Marie
authors: AM
authors: Faussat
authors: Claudia
authors: C
authors: Zuany-Amorim
authors: Zora
authors: Z
authors: Marjanovic
authors: Hamid
authors: H
authors: Morjani
authors: Fanny
authors: F
authors: Fava
authors: Elise
authors: E
authors: Corre
authors: Ollivier
authors: O
authors: Legrand
authors: Jean-Pierre
authors: JP
authors: Marie
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000096:biosynthesis / Q000276:immunology; D015214:Antigens, Differentiation, Myelomonocytic / Q000096:biosynthesis / Q000276:immunology; D003986:Dibenzocycloheptenes / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D018922:HL-60 Cells; D006801:Humans; D018796:Immunoconjugates / Q000493:pharmacokinetics / Q000494:pharmacology*; D020014:K562 Cells; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000378:metabolism*; D008453:Maytansine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D011804:Quinolines / Q000494:pharmacology; D063268:Sialic Acid Binding Ig-like Lectin 3
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D003986:Dibenzocycloheptenes; D018796:Immunoconjugates; D008453:Maytansine; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D011804:Quinolines; D063268:Sialic Acid Binding Ig-like Lectin 3; C116614:ABCG2 protein, human; C571163:CD33 protein, human; C095179:zosuquidar trihydrochloride; C421109:multidrug resistance-associated protein 1