Gang E J, Hsieh Y-T, Pham J, Zhao Y, Nguyen C, Huantes S, Park E, Naing K, Klemm L, Swaminathan S, Conway E M, Pelus L M, Crispino J, Mullighan C G, McMillan M, Müschen M, Kahn M, Kim Y-M
Children's Hospital Los Angeles, Division of Hematology and Oncology, Department of Pediatrics, University of Southern California, Keck School of Medicine, Los Angeles, CA, USA.
Department of Biochemistry and Molecular Biology, Department of Molecular Pharmacology and Toxicology, Norris Comprehensive Cancer Center, Center for Molecular Pathways and Drug Discovery, University of Southern California, Los Angeles, CA, USA.
Oncogene. 2014 Apr 24;33(17):2169-78. doi: 10.1038/onc.2013.169. Epub 2013 Jun 3.
Drug resistance in acute lymphoblastic leukemia (ALL) remains a major problem warranting new treatment strategies. Wnt/catenin signaling is critical for the self-renewal of normal hematopoietic progenitor cells. Deregulated Wnt signaling is evident in chronic and acute myeloid leukemia; however, little is known about ALL. Differential interaction of catenin with either the Kat3 coactivator CREBBP (CREB-binding protein (CBP)) or the highly homologous EP300 (p300) is critical to determine divergent cellular responses and provides a rationale for the regulation of both proliferation and differentiation by the Wnt signaling pathway. Usage of the coactivator CBP by catenin leads to transcriptional activation of cassettes of genes that are involved in maintenance of progenitor cell self-renewal. However, the use of the coactivator p300 leads to activation of genes involved in the initiation of differentiation. ICG-001 is a novel small-molecule modulator of Wnt/catenin signaling, which specifically binds to the N-terminus of CBP and not p300, within amino acids 1-110, thereby disrupting the interaction between CBP and catenin. Here, we report that selective disruption of the CBP/β- and γ-catenin interactions using ICG-001 leads to differentiation of pre-B ALL cells and loss of self-renewal capacity. Survivin, an inhibitor-of-apoptosis protein, was also downregulated in primary ALL after treatment with ICG-001. Using chromatin immunoprecipitation assay, we demonstrate occupancy of the survivin promoter by CBP that is decreased by ICG-001 in primary ALL. CBP mutations have been recently identified in a significant percentage of ALL patients, however, almost all of the identified mutations reported occur C-terminal to the binding site for ICG-001. Importantly, ICG-001, regardless of CBP mutational status and chromosomal aberration, leads to eradication of drug-resistant primary leukemia in combination with conventional therapy in vitro and significantly prolongs the survival of NOD/SCID mice engrafted with primary ALL. Therefore, specifically inhibiting CBP/catenin transcription represents a novel approach to overcome relapse in ALL.
急性淋巴细胞白血病（ALL）中的耐药性仍然是一个需要新治疗策略的主要问题。Wnt/连环蛋白信号传导对于正常造血祖细胞的自我更新至关重要。Wnt信号传导失调在慢性和急性髓细胞白血病中很明显；然而，关于ALL的情况却知之甚少。连环蛋白与共激活因子Kat3 CREBBP（CREB结合蛋白（CBP））或高度同源的EP300（p300）的差异相互作用对于确定不同的细胞反应至关重要，并为Wnt信号通路对增殖和分化的调节提供了理论依据。连环蛋白使用共激活因子CBP会导致参与维持祖细胞自我更新的基因盒的转录激活。然而，使用共激活因子p300会导致参与分化起始的基因激活。ICG-001是一种新型的Wnt/连环蛋白信号传导小分子调节剂，它在氨基酸1-110范围内特异性结合CBP的N端而不结合p300，从而破坏CBP与连环蛋白之间的相互作用。在此，我们报告使用ICG-001选择性破坏CBP/β-和γ-连环蛋白相互作用会导致前B ALL细胞分化并丧失自我更新能力。凋亡抑制蛋白Survivin在用ICG-001治疗后的原发性ALL中也下调。使用染色质免疫沉淀试验，我们证明原发性ALL中CBP占据Survivin启动子，而ICG-001会使其减少。最近在相当比例的ALL患者中发现了CBP突变，然而，几乎所有报告的已鉴定突变都发生在ICG-001结合位点的C端。重要的是，无论CBP突变状态和染色体畸变如何，ICG-001与传统疗法联合使用可在体外根除耐药原发性白血病，并显著延长移植原发性ALL的NOD/SCID小鼠的生存期。因此，特异性抑制CBP/连环蛋白转录代表了一种克服ALL复发的新方法。
