title: Expression of P-glycoprotein in rat hepatocarcinogenesis by diethylnitrosamine and the modulation by anticancer drugs.
abstract: P-glycoprotein (P-GP) is known to be a multidrug resistant 1 gene product and to exhibit resistance to a broad range of drugs including anticancer drugs such as epirubicin. Its overexpression is reported in human hepatocellular carcinoma and in adenomatous hyperplasia of the liver as well. In order to clarify the evolution of P-GP expression during hepatocarcinogenesis and its modulation by anticancer drugs, we performed an immunohistochemical study in male Wistar rat livers exposed to diethylnitrosamine (DEN) for 12 weeks. Some rats were pretreated with cisplatin or epirubicin 1 week prior to the exposure, and some rats were treated with them at the 10th week after the exposure. While there was no P-GP expression in the liver of the control, cisplatin, and epirubicin (DEN-free) rats, expression was confirmed in the hepatocytes of DEN-treated rats. The immunostaining of hyperplastic nodules was significantly more intense than in well-differentiated hepatocellular carcinomas, and no staining was observed in poorly-differentiated carcinomas. Markedly intense staining was observed in the early hyperplastic nodules of cisplatin-pretreated rats, as well as in epirubicin-pretreated rats. Plasma alpha-fetoprotein levels were markedly elevated in DEN-treated rats, while tumor necrosis factor-alpha levels were not. In conclusion, the results suggest that P-GP confers a protective effect against anticancer drugs and provides a great advantage to the initiated cells. Furthermore, in addition to epirubicin, cisplatin also promotes the induction of P-GP in the initiated cell.
authors.affiliation: Second Department of Internal Medicine, Toho University School of Medicine, 6-11-1 Omori-nishi, Ota-ku, 143-8541, Tokyo, Japan
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Takeuchi
authors.forename: Motonobu
authors.initials: M
authors.lastname: Sugimoto
authors.forename: Kaori
authors.initials: K
authors.lastname: Ochiai
authors.forename: Kinji
authors.initials: K
authors.lastname: Ito