Progress in Hematology Efficacy and resistance of molecularly targeted therapy for myeloid malignancies

International Journal of Hematology

, Volume 97, Issue 6, pp 717-725

Mechanisms of action and resistance to all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) in acute promyelocytic leukemia

  • Akihiro TomitaAffiliated withDepartment of Hematology and Oncology, Nagoya University Graduate School of Medicine Email author 
  • , Hitoshi KiyoiAffiliated withDepartment of Hematology and Oncology, Nagoya University Graduate School of Medicine
  • , Tomoki NaoeAffiliated withDepartment of Hematology and Oncology, Nagoya University Graduate School of MedicineClinical Research Center, National Hospital Organization Nagoya Medical Center

Abstract

Since the introduction of all-trans retinoic acid (ATRA) and arsenic trioxide (As2O3) for the treatment of acute promyelocytic leukemia (APL), the overall survival rate has improved dramatically. However, relapse/refractory patients showing resistance to ATRA and/or As2O3 are recognized as a clinically significant problem. Genetic mutations resulting in amino acid substitution in the retinoic acid receptor alpha (RARα) ligand binding domain (LBD) and the PML-B2 domain of PML-RARα, respectively, have been reported as molecular mechanisms underlying resistance to ATRA and As2O3. In the LBD mutation, ATRA binding with LBD is generally impaired, and ligand-dependent co-repressor dissociation and degradation of PML-RARα by the proteasome pathway, leading to cell differentiation, are inhibited. The PML-B2 mutation interferes with the direct binding of As2O3 with PML-B2, and PML-RARα SUMOylation with As2O3 followed by multimerization and degradation is impaired. To overcome ATRA resistance, utilization of As2O3 provides a preferable outcome, and recently, a synthetic retinoid Am80, which has a higher binding affinity with PML-RARα than ATRA, has been tested in the clinical setting. However, no strategy attempted to date has been successful in overcoming As2O3 resistance. Detailed genomic analyses using patient samples harvested repeatedly may help in predicting the prognosis, selecting the effective targeting drugs, and designing new sophisticated strategies for the treatment of APL.

Keywords

APL PML-RARα ATRA Arsenic trioxide (As2O3) Drug resistance