Expression of the erb B oncogene in the Morris hepatoma 7777.
Altered expression of protooncogenes/oncogenes is believed to be involved in hepatocarcinogenesis of the chemically induced, transplantable Morris hepatoma 7777. We compared the mRNA expression of c-N-ras and v-erb B mRNA of normal rat liver with that of Morris hepatoma 7777 using Northern blot analysis and in situ hybridization. Northern blot analysis revealed a strong overexpression of the v-erb B related mRNA, while the c-N-ras mRNA was only slightly increased. In situ hybridization using a c-N-ras mRNA probe also showed only a slightly increased number of silver grains in the hepatoma cells compared with normal rat liver. On the other hand, the v-erb B related mRNA was strongly overexpressed in the hepatoma cells, while the connective-tissue capsule, the blood vessels, blood cells and the necrotic foci did not show an elevated v-erb B related gene mRNA expression. Similar results were obtained in liver metastases. The detectable v-erb B hybridization signal was lost by pretreatment with RNase A. We conclude that the c-N-ras gene is of minor importance in the chemically induced, transplantable Morris hepatoma 7777, while the increased expression of the v-erb B related mRNA is due to a selection of ligand-independent tyrosine kinase activity.
Hocher
B
B
Abteilung für Allgemeine Innere Medizin und Nephrologie, Universitätsklinikum Benjamin Franklin, Freien Universität Berlin, Germany.
Abou-Rebyeh
H
H
Plaum
M
M
Fakhury
M
M
Schiller
S
S
Bauer
C
C
D000818:Animals; D001345:Autoradiography; D001773:Blood Cells / Q000378:metabolism; D015152:Blotting, Northern; D003238:Connective Tissue / Q000378:metabolism; D005260:Female; D005629:Frozen Sections; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics*; D011905:Genes, ras / Q000235:genetics*; D017403:In Situ Hybridization; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000235:genetics* / Q000473:pathology; D008297:Male; D009336:Necrosis; D018739:Oncogene Proteins v-erbB / Q000096:biosynthesis / Q000235:genetics*; D009857:Oncogenes / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000097:blood / Q000378:metabolism; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D011915:Rats, Inbred BUF; D016622:Silver Staining
D018739:Oncogene Proteins v-erbB; D015347:RNA Probes; D012333:RNA, Messenger; D011505:Protein-Tyrosine Kinases