The role of miRNA deregulation in non-genotoxic chemical induced carcinogenesis

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Title: The role of miRNA deregulation in non-genotoxic chemical induced carcinogenesis
Authors: Flores Torres, Mariana
Item Type: Thesis or dissertation
Abstract: MicroRNAs (miRNAs) are short, non-protein coding RNAs. These small-RNAs can regulate gene expression by either inhibiting translation or promoting mRNA degradation, they are also involved in diverse physiological and pathological events. Previous data from our group, showed that phenobarbital (PB, a CAR activator), induces dysregulation of the hepatic miRNAome in rat livers. In this study, we aim to determine if non-genotoxic rodent carcinogens can deregulate miRNA expression. Thus, the liver miRNAome associated with a novel chemical (SYN) and the non-genotoxic rodent carcinogen PB was explored at different doses and time points using high-throughput sequencing of small-RNAs (miRNA seq), a powerful tool for discovery and profiling of miRNA expression, providing a deeper understanding of molecular toxicology. Male Han Wistar rats were treated with PB (50 or 1000 ppm) or SYN (50, 500, and 3000 ppm) in the diet for up to 28 days. Control animals were fed regular diet. Rats were sacrificed after 1, 3, and 28 days. Total RNA was isolated from frozen livers and library constructs were generated with the Illumina platform. The miRanalyzer algorithm and DESeq were used for bioinformatics (for known and novel miRNAs) and statistical analysis. Around 200 known miRNAs were detected per sample. Three key miRNAs related to the epithelial-to-mesenchymal transition (EMT), were detected at the 3rd day –miR-200s, miR 30b, and miR-21. Consequently downregulation of targets related to these RNAs and EMT (ZEB1/2, Snail-1, PTEN, and E-cadherin) was seen. These findings suggest activation of a homeostatic response in EMT control in response to PB/SYN treatment, presumably in order to preserve the epithelial nature of hepatocytes. Analysis of putative novel miRNAs sequences determined three candidates homologous to miR-4488 and a putative isomiRNA of miR-6215. The miRNA-seq approach enables a more detailed exploration of miRNAs and their response to hepatotoxicants, such as PB, helping elucidate underlying pathway perturbations.
Content Version: Open Access
Issue Date: Dec-2015
Date Awarded: Jul-2016
URI: http://hdl.handle.net/10044/1/49224
Supervisor: Gooderham, Nigel
Department: Department of Surgery & Cancer
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Medicine PhD theses



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