Use of a Rainbow Trout Oligonucleotide Microarray to Determine Transcriptional Patterns in Aflatoxin B1-Induced Hepatocellular Carcinoma Compared to Adjacent Liver

Abstract

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, and its occurrence is associated with a number of environmental factors including ingestion of the dietary contaminant aflatoxin B(1) (AFB(1)). Research over the last 40 years has revealed rainbow trout (Oncorhynchus mykiss) to be an excellent research model for study of AFB(1)-induced hepatocarcinogenesis; however, little is known about changes at the molecular level in trout tumors. We have developed a rainbow trout oligonucleotide array containing 1672 elements representing over 1400 genes of known or probable relevance to toxicology, comparative immunology, carcinogenesis, endocrinology, and stress physiology. In this study, we applied microarray technology to examine gene expression of AFB(1)-induced HCC in the rainbow trout tumor model. Carcinogenesis was initiated in trout embryos with 50 ppb AFB(1), and after 13 months control livers, tumors, and tumor-adjacent liver tissues were isolated from juvenile fish. Global gene expression was determined in histologically confirmed HCCs compared to noncancerous adjacent tissue and sham-initiated control liver. We observed distinct gene regulation patterns in HCC compared to noncancerous tissue including upregulation of genes important for cell cycle control, transcription, cytoskeletal formation, and the acute phase response and downregulation of genes involved in drug metabolism, lipid metabolism, and retinol metabolism. Interestingly, the expression profiles observed in trout HCC are similar to the transcriptional signatures found in human and rodent HCC, further supporting the validity of the model. Overall, these findings contribute to a better understanding of the mechanism of AFB(1)-induced hepatocarcinogenesis in trout and identify conserved genes important for carcinogenesis in species separated evolutionarily by more than 400 million years.

Gene expression analyses of hepatocellular adenoma and hepatocellular carcinoma from the marine flatfish Limanda limanda

“…In addition, elevated levels of VTG have also been recorded in the serum from brown bullhead Ameiurus nebulosus with liver tumors (HA and HC) collected from a contaminated industrial site (Heppell et al 1995). Interestingly, Tilton et al (2005) observed that VTG transcription was not elevated in aflatoxin B 1 -induced liver HC from rainbow trout. However, in a subsequent study investigating the effects of 17β-estradiol upon gene expression in aflatoxin B 1 -induced liver HCs, they recorded substantial up-regulation of VTG transcripts (Tilton et al 2007).…”

“…Other orthologous genes significantly changing in expression and known to be involved in carcinogenesis included cathepsin L, 3β-hydroxysteroid dehydrogenase type VII, and a cDNA clone similar to selenoprotein P. Cathepsin L is a protease that is believed to be secreted by cancerous cells to facilitate tumor invasion and metastasis by degrading the components of the extracellular matrix. It has been documented to be up-regulated in a range of human cancers (Chauhan et al 1991) and in HC in rainbow trout (Tilton et al 2005). In humans, the closely related 17β-hydroxysteroid dehydrogenase is responsible for sex steroid metabolism (conversion of active estradiol to the less potent estrone) in normal and tumor tissues.…”

Aflatoxicosis: Lessons from Toxicity and Responses to Aflatoxin B1 in Poultry

“…Both up-and down-regulation of major histocompatibility complex (MHC) class I genes in response to AFB1 exposure was observed in pigs [227], rats [221], and rainbow trout (Oncorhynchus mykiss) [228]. The MHC is a highly polymorphic genomic region that contains genes encoding proteins essential to innate and adaptive immune functions.…”

Gene-expression Analysis Identifies Specific Patterns of Dysregulated Molecular Pathways and Genetic Subgroups of Human Hepatocellular Carcinoma

“…In the last decade, the identification of genes in different types of human cancer has already been performed using this technology (14)(15)(16)(17)(18). In addition, HCC has already been analyzed by microarray techniques (19)(20)(21)(22). Most of these studies have been able to identify further genes putatively involved in hepatocarcinogenesis, but in most cases, specific subgroups of HCC (especially HBV-, HCV-or aflatoxine B-induced HCC) were analyzed.…”