Distinctive gene expression of receptor-type tyrosine kinase families during rat hepatocarcinogenesis.
Growth factor receptor tyrosine kinase signaling plays key roles in regulating growth of normal hepatocytes, however, which receptor-type tyrosine kinase (RTK) is involved in hepatocarcinogenesis remains undetermined. The aim of this study was to characterize the expression of these receptors in different stages of rat liver carcinogenesis. We compared the expression profile of RTK genes in rat normal liver and diethylnitrosamine-induced hepatoma tissues using a homology cloning method with degenerated primers. In situ hybridization, immunohistochemical staining, and RT-PCR were performed to analyze the cell type-specific expression of target RTKs during the chemically-induced hepatocarcinogenesis. Sequence analysis of 459 clones identified 23 different RTK genes. The Tie-2, c-Met, and Flk-1 genes were the most abundant RTK genes cloned in rat hepatoma compared to normal liver. In situ hybridization and immunohistochemical studies showed overexpression of c-Met and Flk-1 in GST-P positive preneoplastic lesions as well as neoplastic lesions. Tie-2 was expressed not only in endothelial cells but also in so-called oval cells, which are thought to be liver stem cells. Tie-2 ligand, angiopointin-1, mRNA was detected in both normal livers and hepatoma cells/tissues. In contrast, angiopoietin-2 mRNA was detected only in hepatoma tissues. These results indicate that c-Met, Tie-2 and Flk-1 signals play important roles in different stages of chemically-induced hepatocarcinogenesis. Distinctive gene expression of RTK may contribute to epigenic implication of hepatoma formation.
Kuroda
Hiroaki
H
Department of Surgery II, Nagasaki University School of Medicine, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Ohtsuru
Akira
A
Futakuchi
Mitsuru
M
Kawashita
Yujo
Y
Nagayama
Yuji
Y
Fukuda
Eiichiro
E
Namba
Hiroyuki
H
Shirai
Tomoyuki
T
Kanematsu
Takashi
T
Yamashita
Shunichi
S
D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D003001:Cloning, Molecular; D004052:Diethylnitrosamine / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D008099:Liver / Q000201:enzymology / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D012334:RNA, Neoplasm; D004052:Diethylnitrosamine; D020794:Receptor Protein-Tyrosine Kinases