Increased expression of the N-myc gene during normal and neoplastic rat liver growth.
The activation of N-myc and c-myc genes has been implicated in the genesis of a variety of cancers. In order to determine whether this activation is related to the process of cell growth, we examined N-myc and c-myc expression in rat hepatocytes when growth was stimulated by partial hepatectomy and in rat liver during neoplastic growth induced by diethylnitrosamine. The levels of N-myc and c-myc mRNAs, which are very low in hepatocytes from normal rats, were increased at least 20-fold within 3 h after partial hepatectomy and decreased rapidly by 6 h. A second transient peak of c-myc and N-myc mRNAs occurred around 9 and 48 h, respectively. N-myc and c-myc expressions were also induced in carcinoma nodules by diethylnitrosamine. A high level of N-myc transcript was observed in hepatocytes as early as 1 month after the carcinogen administration, whereas c-myc transcript was detected at a high level only several months later in carcinoma nodules. Our results suggest that the transient expression of N-myc and c-myc oncogenes during the prereplicative stage of liver regeneration may be associated with the entry of hepatocytes into the cell cycle, and that N-myc expression is not limited to tumors of neural characteristics as has been previously shown but is also observed in cancer from epithelial origin.
Corral
M
M
Institut de Pathologie Moléculaire, Unité Associée CNRS, Faculté de Médecine Cochin-Port-Royal, Paris, France.
Paris
B
B
Guguen-Guillouzo
C
C
Corcos
D
D
Kruh
J
J
Defer
N
N
D000818:Animals; D002455:Cell Division; D002471:Cell Transformation, Neoplastic; D004052:Diethylnitrosamine; D005260:Female; D007700:Kinetics; D008099:Liver / Q000648:ultrastructure*; D008113:Liver Neoplasms / Q000139:chemically induced / Q000473:pathology*; D008115:Liver Regeneration; D009857:Oncogenes; D051381:Rats; D011919:Rats, Inbred Strains; D014158:Transcription, Genetic
D004052:Diethylnitrosamine