Differentially expressed microRNAs in ovine pulmonary adenocarcinoma

Ovine pulmonary adenocarcinoma (OPA) is an infectious neoplastic lung disease of sheep caused by jaagsiekte sheep retrovirus. OPA is an important veterinary problem and is also a valuable large animal model for human lung adenocarcinoma. JSRV infects type 2 alveolar epithelial cells in the lung and induces the growth of tumors, but little is known about the molecular events that lead to the activation of oncogenic pathways in infected cells. MicroRNAs (miRNAs) are small RNA molecules of approximately 22 nucleotides with important roles in regulating gene expression in eukaryotes and with well-established roles in cancer. Here we used small-RNA sequencing to investigate the changes in miRNA expression that occur in JSRV-infected ovine lung. After filtering out low abundance miRNAs, we identified expression of 405 miRNAs, 32 of which were differentially expressed in JSRV-infected lung compared to mock-inoculated control lung. Highly upregulated miRNAs included miR-182, miR-183, miR-96 and miR-135b, which have also been associated with oncogenic changes in human lung cancer. Network analysis of genes potentially targeted by the deregulated miRNAs identified their involvement in pathways known to be dysregulated in OPA. We found no evidence to support the existence of miRNAs encoded by JSRV. This study provides the first information on miRNA expression in OPA and identifies a number of targets for future studies into the role of these molecules in the pathogenesis of this unique veterinary model for human lung adenocarcinoma.