Gianni Maurizio, Fratelli Maddalena, Bolis Marco, Kurosaki Mami, Zanetti Adriana, Paroni Gabriela, Rambaldi Alessandro, Borleri Gianmaria, Rochette-Egly Cecile, Terao Mineko, Garattini Enrico
Laboratory of Molecular Biology, IRCCS-Istituto di Ricerche Farmacologiche "Mario Negri", 20156 Milano, Italy.
Hematology and Bone Marrow Transplant Unit, Azienda Ospedaliera Papa Giovanni XXIII, 24127 Bergamo, Italy.
Oncotarget. 2017 Jun 6;8(23):37041-37060. doi: 10.18632/oncotarget.10556.
Treatment of acute promyelocytic leukemia (APL) with all-trans retinoic acid (ATRA) is the first example of targeted therapy. In fact, the oncogenic fusion-protein (PML-RAR) typical of this leukemia contains the retinoid-nuclear-receptor RARα. PML-RAR is responsible for the differentiation block of the leukemic blast. Besides PML-RAR, two endogenous RARα proteins are present in APL blasts, i.e. RARα1 and RARα2. We developed different cell populations characterized by PML-RAR, RARα2 and RARα1 knock-down in the APL-derived NB4 cell-line. Unexpectedly, silencing of PML-RAR and RARα2 results in similar increases in the constitutive expression of several granulocytic differentiation markers. This is accompanied by enhanced expression of the same granulocytic markers upon exposure of the NB4 blasts to ATRA. Silencing of PML-RAR and RARα2 causes also similar perturbations in the whole genome gene-expression profiles of vehicle and ATRA treated NB4 cells. Unlike PML-RAR and RARα2, RARα1 knock-down blocks ATRA-dependent induction of several granulocytic differentiation markers. Many of the effects on myeloid differentiation are confirmed by over-expression of RARα2 in NB4 cells. RARα2 action on myeloid differentiation does not require the presence of PML-RAR, as it is recapitulated also upon knock-down in PML-RAR-negative HL-60 cells. Thus, relative to RARα1, PML-RAR and RARα2 exert opposite effects on APL-cell differentiation. These contrasting actions may be related to the fact that both PML-RAR and RARα2 interact with and inhibit the transcriptional activity of RARα1. The interaction surface is located in the carboxy-terminal domain containing the D/E/F regions and it is influenced by phosphorylation of Ser-369 of RARα1.
用全反式维甲酸（ATRA）治疗急性早幼粒细胞白血病（APL）是靶向治疗的首个实例。事实上，这种白血病典型的致癌融合蛋白（PML-RAR）包含类视黄醇核受体RARα。PML-RAR导致白血病母细胞的分化阻滞。除了PML-RAR，APL母细胞中还存在两种内源性RARα蛋白，即RARα1和RARα2。我们在源自APL的NB4细胞系中开发了以PML-RAR、RARα2和RARα1敲低为特征的不同细胞群体。出乎意料的是，PML-RAR和RARα2的沉默导致几种粒细胞分化标志物的组成型表达出现类似增加。这伴随着NB4母细胞暴露于ATRA后相同粒细胞标志物表达的增强。PML-RAR和RARα2的沉默还会在载体和ATRA处理的NB4细胞的全基因组基因表达谱中引起类似的扰动。与PML-RAR和RARα2不同，RARα1的敲低会阻断几种粒细胞分化标志物的ATRA依赖性诱导。NB4细胞中RARα2的过表达证实了许多对髓系分化的影响。RARα2对髓系分化的作用不需要PML-RAR的存在，因为在PML-RAR阴性的HL-60细胞中敲低时也会出现这种情况。因此，相对于RARα1，PML-RAR和RARα2对APL细胞分化产生相反的作用。这些相反的作用可能与PML-RAR和RARα2都与RARα1相互作用并抑制其转录活性这一事实有关。相互作用表面位于包含D/E/F区域的羧基末端结构域，并且受RARα1的Ser-369磷酸化影响。
