Altered expression of microRNAs in radiation-induced rat mammary carcinoma

Abstract

Recent studies have showed that microRNAs (miRNAs), a class of short noncoding RNAs, play important roles in tumorigenesis. The epidemiological study on atomic bomb survivors has suggested that the radiation-associated risk for breast cancer incidence is higher than that for most other sites.
In this study, to clarify the involvement of miRNA in radiation-induced mammary tumorigenesis, we analyzed the miRNA expression profiles in radiation-induced rat mammary carcinoma using miRNA microarrays (Agilent Technologies). Mammary carcinomas were collected from Sprague-Dawley rats irradiated with 2 Gy gamma-rays at 7 weeks of age or from nonirradiated rats that spontaneously developed tumors. The miRNA microarray analysis showed that 7 miRNAs were significantly up-regulated in radiation-induced mammary carcinomas compared with spontaneous mammary carcinomas. Of these 7 aberrantly expressed miRNAs, miR-31 and miR-135b showed an increased expression by more than 3-fold. Quantitative PCR analyses confirmed up-regulation of miR-135b. The biological function of miR-135b in vitro is currently under investigation and will be presented.