A Tumor Suppressor Function of LncRNA-X in Bcr-Abl-induced Tumorigenesis

Aberrant long noncoding RNA (lncRNA) expression has been described in many human malignancies, including leukemia. Philadelphia-positive (Ph+) chronic myeloid leukemia (CML) is a stem cell disease induced by Bcr-Abl hybrid gene. Here we attempt to identify lncRNAs associated with CML by analyzing lncRNA expression profiles in K562 cells when Bcr-Abl gene silenced. LncRNA microarray analysis revealed a group of lncRNAs that exhibit Bcr-Abl-dependent expression. In this study, we focused on lncRNA-X that was downregulated by Bcr-Abl, suggesting that lncRNA-X might have a function of tumor suppression. We showed that lncRNA-X over-expression delays Bcr-Abl-induced tumorigenesis in vivo, maybe through its effect on cell survival by modulating STAT5-dependent expression of anti-apoptotic Bcl-XL protein. We also demonstrated that lncRNA-X may affect tumor formation behavior of Bcr-Abl-transformed cells by regulating signaling pathways associated with leukemia stem cells of CML. Together, these results suggest that lncRNA-X suppresses Bcr-Abl-induced tumorigenesis, and the tumor suppressor function of lncRNA-X may be of significance for exploring novel therapeutic strategies for treating CML. This microarray was performed to identify lncRNAs associated with Bcr-Abl-induced chronic myeloid leukemia (CML). Total RNAs were isolated from three independent groups of K562 cells treated with anti-Bcr-Abl or anti-luciferase shRNAs respectively, using TRIzol reagent (Invitrogen, Carlsbad, CA). Samples were amplified and labeled using a NimbleGen One-Color DNA Labeling Kit.

异常长链非编码RNA（long noncoding RNA, lncRNA）的表达异常已在包括白血病在内的多种人类恶性肿瘤中被报道。费城染色体阳性（Philadelphia-positive, Ph+）慢性髓系白血病（chronic myeloid leukemia, CML）是由Bcr-Abl融合基因诱导的干细胞疾病。本研究旨在通过分析Bcr-Abl基因沉默时K562细胞内的lncRNA表达谱，鉴定与CML相关的lncRNA。长链非编码RNA芯片分析揭示了一组受Bcr-Abl调控表达的lncRNA。本研究重点关注了被Bcr-Abl下调的lncRNA-X，提示lncRNA-X可能发挥抑癌作用。本研究证实，lncRNA-X过表达可延缓Bcr-Abl诱导的体内肿瘤发生，这一效应可能通过调控信号转导与转录激活因子5（signal transducer and activator of transcription 5, STAT5）依赖的抗凋亡Bcl-XL蛋白表达、进而影响细胞存活来实现。此外，本研究还发现lncRNA-X可通过调控与CML白血病干细胞相关的信号通路，改变Bcr-Abl转化细胞的成瘤特性。综上，本研究结果表明lncRNA-X可抑制Bcr-Abl诱导的肿瘤发生，其抑癌功能对于探索CML的新型治疗策略具有重要价值。本项芯片实验的目的为鉴定与Bcr-Abl诱导的慢性髓系白血病（CML）相关的lncRNA。实验分别采用抗Bcr-Abl短发夹RNA（short hairpin RNA, shRNA）与抗荧光素酶shRNA处理三组独立的K562细胞样本，使用TRIzol试剂（Invitrogen公司，加利福尼亚州卡尔斯巴德市）提取总RNA。样本通过NimbleGen单通道DNA标记试剂盒完成扩增与标记。