Pancreatic cancer is among the most lethal of all human diseases. With a 5-year survival of less than 6%, there is a dire need for new therapeutic options . Molecular understanding of the disease is vital to overcome barriers to effective treatment. Here we evaluate the expression of noncoding RNAs in patient tissues, cell lines, in vitro model systems and in a genetically engineered mouse model that recapitulates the disease progression in humans. Two different classes of noncoding RNAs were studied, microRNA (miRNA) and transcribed ultraconserved elements (T-UCRs). Corroborating previously published data, we identify a miRNA cluster (miR-216a, miR-216b, and miR- 217) that is consistently down-regulated in the different models of the disease. These miRNAs, are pancreas enriched, and appear to be acinar cell specific. A large percentage of the 482 known T-UCRs had increased expression in pancreatic cancer tissues, cell lines and in an in vitro system that mimics the pancreatic desmoplastic reaction.
We hypothesized that loss of miR-216/-217 expression might be a crucial step in regulating acinar-to-ductal metaplasia (ADM). Although historically believed to originate in the ductal cells, compounding evidence now has shifted the paradigm to an acinar cell origin of the malignancy. miR-216/-217 expression decreases using an in vitro model that mimics the ADM process. Adenovirus overexpression of miR-217 during the in vitro ADM attenuates acinar to epithelial transdifferentiation. We present evidence of indirect regulation of the epithelial cell marker CDH1 by miR-217, suggesting that miR-217 could regulate ADM though suppression of ductal markers in acinar cells. We also considered that the miRNA cluster may target master regulatory transcription factors. We demonstrate that miR-217 targets REST, a major transcriptional suppressor. We show REST protein to be up-regulated in the patient protein analyzed and that REST target genes are up-regulated in gene profiling data from pancreatic cancer patients. Although the relationship needs additional confirmation, these data support a hypothesis where miR-216/-217 regulates genes central to the ADM transition by targeting REST. Finally, to implicate the cluster in PDAC development, we attempted to generate a germline knockout of miR-216/-217. Full homozygous knockout was embryonic lethal, highlighting the importance of these miRNAs in development. Attempts at studying the phenotype of the heterozygous miR-216/-217 knockout were futile as the miRNA expression was not consistently reduced in the pancreas.
Three T-UCRs, UC.190, UC.233 and UC.270 were consistently upregulated in each of the three models systems studied. Hypothesizing that these T-UCRs may be oncogenic, siRNA knockdown of all 3 T-UCRs decreased the viability of MicaPaca-2 cells in vitro, supporting the hypothesis. Moreover, the expression of a large percentage of the T-UCRs increased during in vitro ADM and several of the T-UCRs were modulated by adenoviral expressed miR-217, suggesting direct regulation of the T-UCR by the miRNA during ADM.
|Commitee:||Bloomston, Mark, Goshal, Kalpana, Kvaratskhelia, Mamuka|
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 80/04(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Pharmaceutical sciences, Oncology|
|Keywords:||Cancer, Microrna, Mir-216a, Mir-216b, Mir-217, Pancreas|
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