Genomic analysis of microRNA time-course expression in liver of mice treated with genotoxic carcinogen N-ethyl-N-nitrosourea

Dysregulated expression of microRNA (miRNA) has been extensively detected in human cancer tissues and has shown promise in defining tumor status. It, however, is little known whether and when expression of miRNAs can be changed in normal tissues after carcinogen exposure. To explore possible time-course changes of miRNA expression induced by carcinogens, we treated mice with one dose of 120 mg/kg body weight model genotoxic carcinogen N-ethyl-N-nitrosourea (ENU) and vehicle control. The miRNA expression profiles were determined in the mouse livers in a time-course manner. MiRNAs were isolated from the livers of ENU-treated and control mice at days 1, 3, 7, 15, 30 and 120 after the treatment. The miRNA expressions were determined using RT2-mouse miRNA PCR Array. Principal component analysis of the gene expression profiles showed that miRNA expression at post-treatment days 7 and 15 were different from those at the other time points and the controls. The numbers of the dysregulated miRNAs changed with time, being 3, 5, 14, 32, 5 and 5 at post-treatment days 1, 3, 7, 15, 30 and 120, respectively. Functional analysis of the differentially expressed miRNA at post-treatment days 7 and 15 indicated that the major functions of these ENU-induced dysregulated miRNAs were mainly associated with DNA repair and tumorigenesis, suggesting the microRNA expression is related to genotoxicity of ENU. These results propose that one to two weeks after ENU exposure is the best time for miRNA expression sampling; and that a large number of miRNAs whose expression is dysregulated after carcinogen exposure could be an indicator for carcinogenic damage. Series type: Non-coding RNA profiling by RT-PCR Six-month-old female mice were injected intraperitoneally with a single dose of 120 mg / kg body weight ENU or the vehicle dimethylsulfoxide. Groups of 4 or 5 animals were sacrificed on post-treatment days 1, 3, 7, 15, 30, and 120 for the ENU treatment and post-treatment days 1 and 30 for the control treatment. MicroRNA expressions in the livers were investigated using SABiosciences 384-well Mouse Genome microRNA real-time PCR Array.