Mir-155, The True Expression Vector Construct And Its Function In Pancreatic Cancer A Preliminary Study

MicroRNAs (miRNAs) are a class of 21-25 nucleotide, noncoding small RNAs. They act as posttranscriptional down-regulators of gene expression which are involoved in many physiological and pathological processes such as growth, development, homeostasis and carcinogenesis.MiRNA expression profiles demonstrate that many miRNAs are deregulated in human cancers. Some of them have been shown to function as oncogenes or tumour suppressor genes.miR-155, which is located in chromosome 21q21 was found to be encoded within the phylogenetically conserved region of BIC RNA. BIC gene was originally identified as a common site for insertion of proviral DNA in avian leukosis virus-induced lymphomas. Activation of the BIC gene can accelerate the pathogenesis of lymphomas and leukemias. miR-155 is responsible for the oncogenic activity attributed to BIC RNA.miR-155 is highly expressed in pancreatic cancer. To explore the function of MiR-155, we constructed its eukaryotic expresstion vector by pcDNA4.0/to/his/myc. The sequences of GFP and pre-miR155 were subcloned into the pcDNA4.0/to/his/myc.The precursor of human miR-155 gene was amplified by polymerase chain reaction (PCR) from the human genomic DNA of normal pancreatic tissue .The positive clones were screened by PCR. The new expresstion vector was named pcDNA4.0-m155. To confirm the role of miR-155 in pancreatic cancer cells, we transfected the plasmid into the pancreatic cell lines Panc-1 and Miacapa-2.The miR-155 expression activity was evaluated by observing the biological behavior changes and Western blot . It was showed that pancreatic cancer cells transfected with the pcDNA4.0-m155 had stronger abilities of migration and growth. The result of Western blot suggested us overexpression of miR-155 enchanced the expression of K-RAS. It reminded us that K-RAS might be a possible target for miR-155.