Global DNA methylation profiling of the target renal tubular region for carcinogenicity in rats after 90-day repeated administration of ochratoxin A

Abstract

Ochratoxin A (OTA) induces renal cell tumors after forming karyomegalic tubular cells in the outer stripe of the outer medulla (OSOM) after repeated administration to rats. However, its carcinogenic mechanism remains unclear. In this study, a global gene profiling focusing on DNA methylation was conducted to elucidate the mechanism of OTA-induced renal carcinogenesis. Rats were treated with carcinogenic doses of OTA or 3-monochloropropanediol, a renal carcinogen that does not form karyomegalic cells, for 90 days. RNA-Seq and DNA methylation array analysis were performed on the OSOMs. Among hypermethylated and downregulated genes and hypomethylated and upregulated genes, the expression level was verified for 17 and 25 genes by real-time RT-PCR, respectively. A mitochondrion was found as a gene ontology for the former, which included Acss1, Clpx, and Slc25a23, which promote the TCA cycle and oxidative phosphorylation, suggesting that OTA induced reprogramming of cell metabolism related to the Warburg effect. Gen1, which functions in DNA repair, was also found, suggesting the promotion of chromosomal instability. In contrast, cell adhesion was found as an ontology of hypomethylated and upregulated genes, including Has1, which has been reported to increase centrosome abnormalities and micronucleus formation via intracellular hyaluronic acid production. In summary, multiple genes disrupting DNA methylation were obtained that are involved in the induction of chromosomal instability and cell metabolism aberrations in the OTA-induced renal carcinogenesis.