Very early effect of DMBA and MNU on microRNA expression.

Background: microRNA expression profile analysis provides evaluation of the early stages of carcinogenesis. This study focuses on early alteration of miRNA expression after treatment with different carcinogens. Materials and Methods: Mice were intraperitoneally injected with one dose of 7,12-dimethylbenz(alpha)anthracene (DMBA) and N-methyl-N-nitrosourea (MNU). The expression of miRNAs were analyzed 3 and 6 hours after the treatment, using quantitative real-time-polymerase chain reaction. Results: Underexpression of miR-34a and miR-155 were detected in the liver, spleen and kidneys at 3 and 6 hours after MNU treatment. In the lungs and kidneys, the expression of miR-21 was significantly elevated 6 hours after DMBA treatment, while in the liver, MNU induced higher expression levels of miR-21 at 3 and 6 hours compared to treatment with DMBA. Conclusion: The different response of miRNAs to carcinogens emphasizes their possible role as potential epidemiological biomarkers in early phases of environmental tumorigenesis.