Côté Sylvie, Rosenauer Angelika, Bianchini Andrea, Seiter Karen, Vandewiele Jonathan, Nervi Clara, Miller Wilson H
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis Jewish General Hospital and McGill University Department of Oncology and Medicine, Montreal, Quebec, Canada.
Blood. 2002 Oct 1;100(7):2586-96. doi: 10.1182/blood-2002-02-0614.
Resistance to all-trans retinoic acid (ATRA) remains a clinical problem in the treatment of acute promyelocytic leukemia (APL) and provides a model for the development of novel therapies. Molecular alterations in the ligand-binding domain (LBD) of the PML/RARalpha fusion gene that characterizes APL constitute one mechanism of acquired resistance to ATRA. We identified missense mutations in PML/RARalpha from an additional ATRA-resistant patient at relapse and in a novel ATRA-resistant cell line, NB4-MRA1. These cause altered binding to ligand and transcriptional coregulators, leading to a dominant-negative block of transcription. These mutations are in regions of the LBD that appear to be mutational hot spots occurring repeatedly in ATRA-resistant APL patient cells. We evaluated whether histone deacetylase (HDAC) inhibition could overcome the effects of these mutations on ATRA-induced gene expression. Cotreatment with ATRA and TSA restored RARbeta gene expression in NB4-MRA1 cells, whose PML/RARalpha mutation is in helix 12 of the LBD, but not in an APL cell line harboring the patient-derived PML/RARalpha mutation, which was between helix 5 and 6. Furthermore, ATRA combined with TSA increases histone 4 acetylation on the RARbeta promoter only in NB4-MRA1 cells. Consistent with these results, the combined treatment induces differentiation of NB4-MRA1 only. Thus, the ability of an HDAC inhibitor to restore ATRA sensitivity in resistant cells may depend on their specific molecular defects. The variety of PML/RARalpha mutations arising in ATRA-resistant patients begins to explain how APL patients in relapse may differ in response to transcription therapy with HDAC inhibitors.
对全反式维甲酸（ATRA）的耐药性仍是急性早幼粒细胞白血病（APL）治疗中的一个临床问题，并为新型疗法的开发提供了一个模型。表征APL的PML/RARα融合基因的配体结合域（LBD）中的分子改变构成了对ATRA获得性耐药的一种机制。我们在一名复发的额外ATRA耐药患者以及一个新的ATRA耐药细胞系NB4-MRA1中鉴定出PML/RARα中的错义突变。这些突变导致与配体和转录共调节因子的结合改变，从而导致转录的显性负性阻断。这些突变位于LBD中似乎是ATRA耐药APL患者细胞中反复出现的突变热点区域。我们评估了组蛋白脱乙酰酶（HDAC）抑制是否能克服这些突变对ATRA诱导的基因表达的影响。ATRA与曲古抑菌素A（TSA）联合处理可恢复NB4-MRA1细胞中的RARβ基因表达，其PML/RARα突变位于LBD的螺旋12中，但在携带患者来源的PML/RARα突变（位于螺旋5和6之间）的APL细胞系中则不能恢复。此外，ATRA与TSA联合处理仅在NB4-MRA1细胞中增加RARβ启动子上组蛋白4的乙酰化。与这些结果一致，联合处理仅诱导NB4-MRA1细胞分化。因此，HDAC抑制剂恢复耐药细胞中ATRA敏感性的能力可能取决于它们特定的分子缺陷。ATRA耐药患者中出现的多种PML/RARα突变开始解释复发的APL患者对HDAC抑制剂转录治疗的反应可能存在差异的原因。
