Xiao Haowen, Ding Yingying, Gao Yang, Wang Li-Mengmeng, Wang Huafang, Ding Lijuan, Li Xiaoqing, Yu Xiaohong, Huang He
1Department of Hematology, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, No. 3 Qingchun East Rd., Hangzhou, 310016 Zhejiang People's Republic of China.
2Institute of Hematology, Zhejiang University, Hangzhou, Zhejiang People's Republic of China.
Cancer Cell Int. 2019 Aug 23;19:218. doi: 10.1186/s12935-019-0940-9. eCollection 2019.
Relapse represents the leading cause of death in both child and adult patients with acute lymphoblastic leukemia (ALL). Development of chemo-resistance is ultimately responsible for treatment failure and relapse, therefore understanding the molecular basis underlying resistance is imperative for developing innovative treatment strategies. Glucocorticoids (GCs) such dexamethasone and prednisolone are the backbone of combination chemotherapy regimens for treating all lymphoid tumors. However, the biological mechanisms of primary GC resistance in ALL is not completely understood. We previously performed a longitudinal whole-exome sequencing analysis on diagnosis/relapse pairs from adult patients with ALL. Our data revealed that relapse-specific truncation mutations in the gene, encoding the GC receptor, are frequently detected.
In the current study, we used discovery-based strategies including RNA sequencing (RNA-seq) and CRISPR/Cas9, followed by confirmatory testing, in human ALL cell lines, bone marrow blast samples from ALL patients and xenograft models, to elucidate the mechanisms responsible for resistance.
Our results revealed a positive correlation between endogenous expression of in ALL cells and sensitivity to GCs and clinical outcomes. We further confirmed that ectopic expression of in ALL cells could reverse GC resistance, while deletion of confers resistance to GCs in ALL cell lines and xenograft models. RNA-seq analysis revealed a remarkable abundance of gene signatures involved in pathways in cancer, DNA replication, mismatch repair, P53 signalling, cell cycle, and apoptosis regulated by Significantly increased expression of pro-apoptotic genes including , , , and , and decreased transcription of anti-apoptotic genes including , and were observed in GC-resistant ALL cells following ectopic expression of . Finally, we explored that GC resistance in ALL cells with haploinsufficiency of can be treated with Bcl-2 blockage.
Our findings suggest that the status of gene mutations and basal expression levels of in ALL cells are associated with sensitivity to GCs and clinical treatment outcomes. Early intervention strategies by rational combination of Bcl-2 blockage may constitute a promising new treatment option to GC-resistant ALL and significantly improving the chances of treating poor prednisone responders.
复发是儿童和成人急性淋巴细胞白血病（ALL）患者的主要死亡原因。化疗耐药的出现最终导致治疗失败和复发，因此了解耐药的分子基础对于制定创新治疗策略至关重要。地塞米松和泼尼松龙等糖皮质激素（GCs）是治疗所有淋巴瘤的联合化疗方案的基础。然而，ALL中原发性GC耐药的生物学机制尚未完全明确。我们之前对成年ALL患者的诊断/复发配对样本进行了纵向全外显子测序分析。我们的数据显示，经常检测到编码GC受体的基因中的复发特异性截断突变。
在本研究中，我们在人ALL细胞系、ALL患者的骨髓原始细胞样本和异种移植模型中，采用基于发现的策略，包括RNA测序（RNA-seq）和CRISPR/Cas9，随后进行验证性测试，以阐明耐药机制。
我们的结果显示，ALL细胞中该基因的内源性表达与对GCs的敏感性及临床结果呈正相关。我们进一步证实，ALL细胞中该基因的异位表达可逆转GC耐药，而在ALL细胞系和异种移植模型中该基因的缺失则赋予对GCs的耐药性。RNA-seq分析显示，大量与癌症、DNA复制、错配修复、P53信号传导、细胞周期以及由该基因调控的凋亡相关的基因特征显著丰富。在该基因异位表达后的GC耐药ALL细胞中，观察到促凋亡基因（包括、、、和）的表达显著增加，而抗凋亡基因（包括、和）的转录减少。最后，我们探究了该基因单倍体不足的ALL细胞中的GC耐药可通过Bcl-2阻断来治疗。
我们的研究结果表明，ALL细胞中该基因突变状态和该基因的基础表达水平与对GCs的敏感性及临床治疗结果相关。通过合理联合Bcl-2阻断进行早期干预策略可能构成一种有前景的新治疗选择，用于治疗GC耐药ALL，并显著提高治疗泼尼松反应不佳者的机会。
