Kent Oliver A, Mendell Joshua T, Rottapel Robert
Princess Margaret Cancer Centre, University Health Network, Toronto Medical Discovery Tower, University of Toronto, Toronto, Ontario, Canada.
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas. Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas. Center for Regenerative Science and Medicine, University of Texas Southwestern Medical Center, Dallas, Texas. Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas.
Mol Cancer Res. 2016 Mar;14(3):267-77. doi: 10.1158/1541-7786.MCR-15-0456. Epub 2016 Jan 8.
Activating KRAS mutations are nearly ubiquitous in pancreatic cancer occurring in more than 95% of clinical cases. miRNAs are small noncoding RNAs that regulate gene expression by binding sequences within the 3'UTRs of target mRNAs. An integral role for miRNAs in cancer pathogenesis is well established; however, the role of miRNAs in KRAS-mediated tumorigenesis is poorly characterized. Here it is demonstrated that expression of miR-31 is coupled to the expression of oncogenic KRAS and activity of the MAPK pathway. miR-31 is highly expressed in patient-derived xenografts and a panel of pancreatic and colorectal cancer cells harboring activating KRAS mutations. The miR-31 host gene is a large noncoding RNA that correlates with miR-31 expression and enabled identification of the putative miR-31 promoter. Using luciferase reporters, a minimal RAS-responsive miR-31 promoter was found to drive robust luciferase activity dependent on expression of mutant KRAS and the transcription factor ELK1. Furthermore, ELK1 interacts directly with the endogenous miR-31 promoter in a MAPK-dependent manner. Expression of enforced miR-31 significantly enhanced invasion and migration of multiple pancreatic cancer cells resulting from the activation of RhoA through regulation of the miR-31 target gene RASA1. Importantly, acute knockdown of RASA1 phenocopied enforced miR-31 expression on the migratory behavior of pancreatic cancer cells through increased RhoA activation.
Oncogenic KRAS can activate Rho through the miR-31-mediated regulation of RASA1 indicating miR-31 acts as a KRAS effector to modulate invasion and migration in pancreatic cancer.
激活型KRAS突变在胰腺癌中几乎普遍存在，超过95%的临床病例都有发生。微小RNA（miRNA）是一类小的非编码RNA，通过与靶mRNA的3'非翻译区（3'UTR）内的序列结合来调节基因表达。miRNA在癌症发病机制中的重要作用已得到充分证实；然而，miRNA在KRAS介导的肿瘤发生中的作用却鲜为人知。本文证明，miR-31的表达与致癌性KRAS的表达及丝裂原活化蛋白激酶（MAPK）途径的活性相关。miR-31在患者来源的异种移植瘤以及一组携带激活型KRAS突变的胰腺和结肠癌细胞中高表达。miR-31宿主基因是一种大型非编码RNA，与miR-31表达相关，并有助于鉴定假定的miR-31启动子。利用荧光素酶报告基因，发现一个最小的RAS反应性miR-31启动子可驱动强大的荧光素酶活性，该活性依赖于突变型KRAS和转录因子ELK1的表达。此外，ELK1以MAPK依赖的方式直接与内源性miR-31启动子相互作用。强制表达miR-31显著增强了多种胰腺癌细胞的侵袭和迁移能力，这是通过调控miR-31靶基因RASA1激活RhoA所致。重要的是，急性敲低RASA1可模拟强制表达miR-31对胰腺癌细胞迁移行为的影响，这是通过增加RhoA激活实现的。
致癌性KRAS可通过miR-31介导的RASA1调节激活Rho，表明miR-31作为KRAS效应因子调节胰腺癌的侵袭和迁移。
