Study On The Effect And Mechanism Of MiR-150on The Pathogenesis Of Pancreatic Cancer By Targeting C-Myb And MUC4

Background and aims:Pancreatic cancer (PC) is a highly malignant tumor, and the incidence is on the riseat home and abroad. Due to the aggressive nature of this neoplasia, the lack of methodsfor early detection, and the limited response to available treatments, PC is a devastatinghuman malignancy with high mortality rate. It’s necessary to understand the molecularmechanisms of pancreatic cancer, especially in prevention, early diagnosis, and bettertreatment of patients with early-stage tumors.Recently, there is a growing recognition of the important role of miRNAs inregulating their target mRNAs at a posttranscriptional level as an abundant class ofendogenous small non-coding, single-stranded RNAs. Many miRNAs have been shown tobe involved in cancer, acting either as oncogenes or tumor suppressors. There are obviousdifferences of miRNA expression proifles between tumor cells and normal tissue cells，andhuman miRNA genes are frequently located in fragile sites and genomic regions involvedin cancers. All of these may prompt that the full complement of miRNAs in a genome maybe extensively involved in cancers and the miRNA genes may act critical roles in cancers.MiR-150is recently identiifed as an oncogene and tumor suppressor in different typesof cancers. The previously published ifndings reveal that miR-150is up-regulated ingastric cancer, osteosarcoma, colorectal cancers with liver metastases, craniopharyngioma,hepatoblastoma, chronic lymphocytic leukemia and conjunctival MALT lymphoma.However, in contrast, down-regulation of miR-150was reported in mantle cell lymphoma,Hodgkin lymphoma, childhood acute lymphoblastic leukemia, chronic myeloid leukemia,colorectal cancers and NK/T-cell lymphoma. These opposing effects of miR-150onmalignant tumors may be attributed to its numerous targets in different cell types or underdifferent circumstances. The proven targets of miR-150are c-Myb，MUC4，EGR2，DKC1and AKT2. The transcription factor gene c-Myb has been demonstrated to be anevolutionary conserved target of miR-150. Ectopic expression of miR-150in breast cancerand leukemic cells represses endogenous c-Myb at both messenger RNA (mRNA) andprotein levels. It has been reported that the down-regulation of miR-150’s could contributeto the over-expression of c-Myb, which is observed in chronic myeloid leukemia (CML)and carcinomas of the breast, head and neck. It has also been reported thatmiR-150-mediated MUC4’s down-regulation is associated with tumors growth and metastasis. Based on our previous results, we propose that miR-150may function at themRNA regulation level to suppress c-Myb and MUC4gene expression in pancreaticcancers.A limited number of reports have investigated the role of miR-150in pancreaticcancer. The purpose of this study is to examine the relationship between the expressionof miR-150and its carcinogenesis role in pancreatic cancer, the associations of theexpression of its predicted targets c-Myb and MUC4and patients’ clinic-pathologicaldata.Materials and Methods:1.In situ hybridization (ISH) and immunohistochemistry were performed to conifrm theexpressions of miR-150and its predicted targets c-Myb and MUC4in two panels ofpancreatic cancers and adjacent benign pancreas tissues microarray. The association ofmiR-150, c-Myb and MUC4expressions and all patients’ clinic-pathological data wasinvestigated.2.Loss-and gain-of-function studies on miR-150in pancreatic cancer cell lines wereused to characterize its effect on pancreatic cancer proliferation and malignant behaviorusing MTT assay, lfow cytometry, colony formation, migration and invasion assay,respectively.3.The tumorigenicity of pancreatic cancer cells was assessed by xenografts in nude miceexperiments to examine the effect of miR-150on tumorigenesis of pancreatic cancers.Results:1. We observed down-regulation of miR-150and up-regulations of c-Myb and MUC4inpancreatic cancer compared to adjacent benign pancreas tissue. MiR-150frequency wasinversely correlated with c-Myb and MUC4. There is not obvious relationship between theexpression of miR-150, c-Myb and MUC4and clinicopathological characteristics ofpancreatic cancer patients such as gender, age, mass location, tumor size，celldifferentiation, TNM stage, lymph node metastasis, neural invasion, distant metastasis andso on. The pancreatic cancer patients whose expression of miR-150is higher can stay alivelonger than those whose miR-150is lower. And it looks like that the patients whoseexpressions of c-Myb and MUC4is higher usually stay alive a little shorter than the thosewhose expression of c-Myb and MUC4is lower. But there is also no signiifcant differencein overall survival rate between c-Myb and MUC4negative groups and the positive ones. 2.Through in vitro and in vivo experiments, we demonstrated that the over-expression ofmiR-150leads to reduced growth, clonogenicity，migration, invasion, modulates cell cycleand promotes apoptosis in pancreatic cancer cells. Moreover, we identiifed the reciprocalexpression of c-Myb，MUC4and miR-150in this regulation.3.MiR-150suppressed the growth of pancreatic cancer in vivo. Additionally, we found thereciprocal expression pattern of c-Myb, MUC4and miR-150in tumor nodules.Conclusions:1.The expression of miR-150was down-regulated in pancreatic ductal adenocarcinomatissues, suggesting that miR-150may negatively regulate the occurrence and developmentof pancreatic cancer.2.MiR-150inhibited growth and malignant behavior of pancreatic cancer cells，acting as apotential tumor suppressor gene.3.Our ifndings established miR-150as a regulator of c-Myb and MUC4in pancreaticcancer. MiR-150may function by regulating c-Myb and MUC4expressions negatively.4.Clinical large sample of pancreatic cancer shows that the expressions of miR-150andthe prognosis of pancreatic cancer patients are relevant very likely.5.MiR-150and its targets, c-Myb and MUC4, might represent novel molecular biomarkersor targets for drug development in pancreatic cancer.