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(α)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.