Differential expression of microRNAs in xenografted Lewis lung carcinomas subjected to intermittent hypoxia: a next-generation sequence analysis

Background: Obstructive sleep apnea (OSA) is associated with increased cancer mortality, but the underlying mechanism remains poorly understood. MicroRNAs (miRNAs) are confirmed to be involved in tumorigenesis and tumor progression. However, whether miRNAs have any differential expressions in OSA population needs to be elucidated. The aim of this experimental study was to determine the alterations of various miRNAs in xenograft mice exposed to chronic intermittent hypoxia (IH) which is considered a hallmark of OSA. Methods: Sequencing was applied to screen the miRNAs of tumor tissues in xenograft mice exposed to IH and normoxia (control, CTL), respectively. Most differentially expressed miRNAs were verified by the quantitative real-time polymerase chain reaction (qRT-PCR). Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway were performed to reveal the functional enrichment of the target genes regulated by the miRNAs. Results: A total of 485 miRNAs (259 novel miRNAs and 226 known miRNAs) were differentially expressed between the IH and CTL groups. 154 miRNAs were upregulated and 331 miRNAs were downregulated among them. The top 5 differentially expressed known (miR-767, miR-466f-5p, miR-5122, miR-124-3p and miR-590-3p) and novel (miR-140, miR-130, miR-301, miR-177 and miR-90) miRNAs were validated by qRT-PCR. MiR-767, miR-124-3p, miR-590-3p and all novel miRNAs were upregulated while miR-466f-5p and miR-5122 were downregulated in IH-induced xenograft mice. In addition, GO and KEGG pathway analysis demonstrated that the predicted target genes, which were regulated by differentially expressed miRNAs were markedly enriched in related biological processes and pathways, including biological processes, cell metabolic and biosynthetic processes and molecular functions. Conclusions: Several altered miRNAs were detected in xenograft mice exposed to IH. The differentially expressed miRNAs in IH indicates that these miRNAs might involve in the molecular mechanism of tumorigenesis and tumor progression in OSA. Further studies are required to determinate the exact intermediation of certain miRNAs between IH and tumor progression.