Orphan nuclear receptor constitutive active/ androstane receptor-mediated alterations in DNA methylation during phenobarbital promotion of liver tumorigenesis

Altered DNA methylation is an epigenetic mechanism that plays a key role in the carcinogenesis process, and the non-genotoxic rodent hepatocarcinogen phenobarbital (PB) alters the methylation status of DNA in mouse liver. The constitutive active/ androstane nuclear receptor (CAR) mediates half of the PB-induced hepatic gene expression changes and it is essential for liver tumor promotion in PB-treated mice. Here, a technique involving methylation-sensitive restriction digestion, arbitrarily primed PCR, and capillary electrophoresis was utilized to detect PB-induced regions of altered DNA methylation (RAMs) in CAR wildtype (WT) mice that are sensitive to promotion by PB and resistant CAR knockout (KO) mice. The CAR WT mice de-veloped preneoplastic lesions after 23 weeks of PB treatment (precancerous) and liver tumors after 32 weeks, while the CAR KO mice did not develop tumors (Y. Yamamoto, et al., 2004