Mutations in the E-Domain of RARα Portion of the PML/RARα Chimeric Gene May Confer Clinical Resistance to All-transRetinoic Acid in Acute Promyelocytic Leukemia

Abstract

The binding of all-trans retinoic acid (ATRA) to the ligand-binding region in the E-domain of retinoic acid receptor-α (RARα) modifies the transcriptional activity of RARα protein. ATRA probably induces differentiation of acute promyelocytic leukemia (APL) cells by binding to the E-domain of the RARα portion (RARα/E-domain) of PML/RARα chimeric protein. Therefore, molecular alteration in the RARα/E-domain of the chimeric gene is one mechanism by which patients with APL may acquire resistance to ATRA therapy. In this study using reverse transcription-polymerase chain reaction and single-strand conformation polymorphism, DNA segments amplified from the RARα/E-domain in fresh APL cells of 23 APL patients (8 males and 15 females from 4 to 76 years of age) were screened for mutations. Of those patients, 3 patients (1 with de novo and 2 with relapse) had clinical resistance to ATRA therapy. We found mutations in the RARα/E-domain of PML/RARα chimeric gene exclusively in the 2 patients who exhibited ATRA-resistance at relapse, whereas the mutations were not detected at their initial onset. Interestingly, these patients received a prolonged or intermittent administration of ATRA before relapse with ATRA-resistance. The mutations lead to the change of amino acid in the ligand-binding region of RARα/E-domain, Arg272Gln, or Met297Leu according to the amino acid sequence of RARα, respectively. Further study demonstrated that the in vitro ligand-dependent transcriptional activity of the mutant PML/RARα protein was significantly decreased as compared with that of wild-type PML/RARα. These findings suggest that mutations in the RARα/E-domain of the PML/RARα chimeric gene may confer clinical resistance to ATRA therapy in patients with APL.

Analysis of gene profiles involved in the enhancement of all-trans retinoic acid-induced HL-60 cell differentiation by sesquiterpene lactones identifies asparagine synthetase as a novel target for differentiation-inducing therapy

“…This drug has been shown to cause terminal differentiation of immature leukemic blasts by regulating many target genes including retinoic acid receptor, CCAAT/enhancer-binding protein β and interferon regulatory factor 1 (5-7). Although it has been established that there is a high rate of complete remission with the administration of ATRA, there are several reports of adverse effects such as differentiation syndrome, hypercalcemia and ATRA resistance (8)(9)(10)(11). Therefore, combination therapy of ATRA with alternative medicines has been suggested to minimize these unexpected effects (12).…”

Altered nuclear cofactor switching in retinoic‐resistant variants of the PML‐RARα oncoprotein of acute promyelocytic leukemia

“…ATRA‐resistant mutants of PML‐RARα that localized to the RARα LBD included variants derived from ATRA‐resistant isolates of the PML‐RARα cell line NB‐4, and from ATRA‐treated and relapsed patients 35. 44–46 Four mutants that encompass different regions of the RARα LBD were selected for this study, consisting of L398P, M297L, I410T, and M413T. Their locations in the RARα LBD structure are indicated in Figure 1.…”

Retinoids in Oral Diseases: An Enigmatic Role in Chemoprevention

“…It is also suggested that P-gylcoprotein decrease the attained concentration of RA intracellularly by immediate or early flushing [77]. Latest hypothesis about resistance to RA state that point mutation in ligand binding domain of RAR-α might be associated with relapse in Acute Promyelocytic Leukemia (APL) cells [78,79,80]. Intrinsic retinoid resistance is also suggested to be lined with free oxygen species present inside the cell which tend to inhibit cell metabolism [81].…”