Yin W, Rossin A, Clifford J L, Gronemeyer H
Department of Cell Biology and Signal Transduction, Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC/CNRS/INSERM/ULP, Illkirch Cedex, C U de Strasbourg, France.
Oncogene. 2006 Jun 22;25(26):3735-44. doi: 10.1038/sj.onc.1209410. Epub 2006 Jan 30.
Retinoic acid (RA), used as first-line therapy for acute promyelocytic leukemia (APL), exerts its antileukemic activity by inducing blast differentiation and activating tumor-selective TNF-related apoptosis-inducing ligand (TRAIL) signaling. To identify downstream mediators of RA signaling, we used retrovirus-mediated insertion mutagenesis in PLB985 leukemia cells and established the RA-resistant cell line WY-1. In PLB985, but not WY-1 cells, RA induced TRAIL and its DR4 and DR5 receptors. Knocking down TRAIL expression by RNA interference blocked RA-induced apoptosis. WY-1 cells are defective for RA-induced differentiation, G1 arrest and exhibit co-resistance to TRAIL. In WY-1 cells, a single virus copy is integrated into a novel RA-regulated gene termed RAM (retinoic acid modulator). RAM is expressed in the myelomonocytic lineage and extinguished by RA in PLB985, but not WY-1 cells. Whereas knocking down RAM expression by RNA interference promoted RA-induced differentiation and TRAIL-triggered apoptosis of PLB985 and WY-1 cells, overexpression of the predicted 109 amino-acid RAM open reading frame did not alter RA signaling in PLB985 cells. This indicates that, apart from encoding the putative RAM protein, RAM RNA may exert additional functions that are impaired by the retrovirus insertion. Our study demonstrates that RA induction of the TRAIL pathway is also operative in leukemia cells lacking an RARalpha oncofusion protein and identifies RAM as a novel RA-dependent modulator of myeloid differentiation and death.
维甲酸（RA）作为急性早幼粒细胞白血病（APL）的一线治疗药物，通过诱导原始细胞分化和激活肿瘤选择性肿瘤坏死因子相关凋亡诱导配体（TRAIL）信号传导发挥其抗白血病活性。为了鉴定RA信号的下游介质，我们在PLB985白血病细胞中使用逆转录病毒介导的插入诱变，并建立了RA抗性细胞系WY-1。在PLB985细胞而非WY-1细胞中，RA诱导TRAIL及其DR4和DR5受体。通过RNA干扰敲低TRAIL表达可阻断RA诱导的细胞凋亡。WY-1细胞在RA诱导的分化、G1期阻滞方面存在缺陷，并对TRAIL具有共同抗性。在WY-1细胞中，单个病毒拷贝整合到一个新的RA调节基因中，称为RAM（维甲酸调节剂）。RAM在骨髓单核细胞系中表达，在PLB985细胞中可被RA消除，但在WY-1细胞中则不会。虽然通过RNA干扰敲低RAM表达可促进PLB985和WY-1细胞的RA诱导分化和TRAIL触发的细胞凋亡，但预测的109个氨基酸的RAM开放阅读框的过表达并未改变PLB985细胞中的RA信号传导。这表明，除了编码假定的RAM蛋白外，RAM RNA可能发挥其他功能，而这些功能因逆转录病毒插入而受损。我们的研究表明，RA对TRAIL途径的诱导在缺乏RARα癌融合蛋白的白血病细胞中也起作用，并将RAM鉴定为髓系分化和死亡的新型RA依赖性调节剂。
