LncRNA GLS-AS介导m6A去甲基化在酸性微环境诱导胰腺癌代谢重编程中作用及机制

The metabolism reprogramming is closely correlated with tumorigenesis of pancreatic cancer, while its regulatory mechanism is undefined. We previously discovered that the metabolism of glutamine was significantly enhanced by the acidic microenvironment. Moreover, the low concentration of glutamine obviously retarded the proliferation and invasion ability of pancreatic cancer cells. Meanwhile, the expression of glutaminase (GLS) and its antisense lncRNA (GLS-AS) were remarkably upregulated during acidic microenvironment. Recently, research reported that the stability of mRNA can be regulated by m6A methylation decoration. Interestingly, we also discovered that the m6A methylation of GLS-mRNA was increased by the knockdown of GLS-AS, while the expression of GLS was inhibited. Furthermore, the bioinformatic dataset predicted that the demethylation protein FTO is potentially bound to GLS-AS. Therefore, we hypothesis that GLS-AS may enhance stability and expression of GLS-mRNA by FTO-dependent m6A demethylation, which is consequently involved in the acidity-induced metabolism reprogramming of pancreatic cancer. In the present study, we will evaluate the expression of acidity/GLS-AS/FTO/GLS axis in the pancreatic cancer tissues, and further investigate the mechanism of the axis in acidity-mediated metabolic reprogramming. Furthermore, the effects of modulating the expression of acidity/GLS-AS/FTO/GLS axis on tumorigenesis of pancreatic cancer will be assessed. By focusing on the role of metabolism reprogramming and lncRNA-mediated m6A methylation, the present study will intensively investigate the function of microenvironment in tumorigenesis of pancreatic cancer. This research will enhance the understanding of RNA epitranscriptome in the mutual regulation between microenvironment and tumor.

细胞代谢重编程与肿瘤发病密切相关，其机制尚未明确。本课题组发现酸性微环境显著增强胰腺癌细胞谷氨酰胺代谢，其增殖与侵袭能力依赖于谷氨酰胺；且谷氨酰胺酶GLS及其反义LncRNA（GLS-AS）表达上调。研究表明m6A甲基化修饰参与调控mRNA稳定。我们发现敲低GLS-AS可促进GLS-mRNA的m6A甲基化，抑制GLS表达；生物信息预测GLS-AS可结合m6A去甲基化酶FTO。由此推测，GLS-AS通过FTO诱导m6A去甲基化，促进GLS-mRNA稳定与表达，介导酸性微环境调控谷氨酰胺代谢重编程。拟检测胰腺癌中酸性/GLS-AS/FTO/GLS信号轴表达，研究其介导酸性微环境调控代谢重编程机制，探讨以上述信号轴为调控靶点对胰腺癌发生发展的影响。项目以代谢重编程为切入点，从非编码RNA调控m6A甲基化角度，探讨酸性微环境在胰腺癌中作用，有助于深入理解RNA表观调控在肿瘤与微环境交叉对话中作用。

已有研究表明，恶行肿瘤细胞会发生代谢重编程，如有氧糖酵解和谷氨酰胺依赖，以维持肿瘤快速增殖和转移。目前尚不清楚长链非编码RNA (lncRNA)是否参与胰腺癌的代谢重编程。在本研究，我们确定了一个核富集的谷氨酰胺酶反义lncRNA (GLS-AS)作为胰腺癌代谢的关键调节因子。与非癌性周围组织相比，胰腺癌组织中GLS-AS下调。在体外和裸鼠异种移植瘤中，GLS-AS的缺失均促进了胰腺癌细胞的增殖和侵袭。GLS-AS通过ADAR/ dicer依赖性RNA干扰，与GLS pre-mRNA形成双链RNA，在转录后水平抑制GLS的表达。营养应激诱导的Myc在转录水平抑制GLS-AS表达。相反，GLS-AS通过破坏GLS介导的Myc蛋白的稳定性来降低Myc的表达。综上所述，在营养应激下，Myc和GLS-AS调节GLS过表达，形成互反馈环路。GLS- AS异位过表达通过抑制Myc/GLS通路抑制胰腺癌细胞增殖和侵袭。此外，GLS-AS与GLS在胰腺癌临床样本中的表达呈负相关，GLS-AS低表达与较差的临床预后相关。我们的研究揭示了一种新的lncRNA介导的Myc/GLS通路，它可能作为胰腺癌治疗的代谢靶点，并促进了我们对lncRNA在营养应激和肿瘤发生中耦合作用的理解。