Alteration in MicroRNA Expression Pattern in CD-1 Mouse Fetal Liver Cells Following In Vitro Benzoquinone Exposure
Benzene, Fetal liver, microRNA
The incidence of childhood leukemias in developed countries is increasing and in utero exposure to environmental toxicants such as benzene may be primarily responsible. The mechanism behind benzene- induced hematotoxicity is not completely understood, however, previous work from our laboratory has demonstrated that following in utero exposure to benzene, CD-1 mice one year after birth had an increased incidence of hematopoietic tumours. This suggests that molecular changes before birth could be responsible for the development of childhood leukemias. The objective of this thesis was to investigate whether altered MicroRNA (miR) expression following exposure to benzoquinone (BQ) in fetal hematopoietic cells is a potential pathway by which environmental toxicants could initiate in utero carcinogenesis. To test this, fetal liver cells isolated from gestational day (GD) 14 CD-1 fetal mice were exposed to BQ in vitro for 3 hours. The identification of largescale expression pattern changes in miR expression pattern in a subset of miRs was then conducted using a hybridization array plate. The finding that BQ was able to alter miRs in fetal liver cells led us to examine specific miRs identified in the literature to be associated with hematotoxicity, including miR-146a, miR-155, and miR-19b. Evaluation of miRs through qRT-PCR identified significant increases in miR-155 and miR-19b in fetal hematopoietic cells following 6 hours of BQ exposure, however no difference was observed in miR-146a expression at any time point. To investigate if the miR expression change had decreased downstream mRNA targets, we evaluated targets of miR-155 (c-Myb and Sfpi1) and miR-19b (Pten). There was no statistically significant differences in any of the mRNA evaluated, however there was a trend towards decreased levels of c-Myb and Sfpi1 mRNA expression following BQ exposure for 6 hours, correlating with the time of increased miR-155 expression. This study reveals miRs as a potential mechanism of benzene-induced hematotoxicity, and highlights the importance of continuing to understand the mechanisms for in utero benzene-initiated hematotoxicity for potential therapeutic targets.