Signal Transduction by the Epidermal Growth Factor Receptor 
a copy of the truncated receptor gene can also 
occur. This truncated gene is the dominantly ac- 
tive oncogene erbB. The primary disease asso- 
ciated with erbB is erythroblastosis. However, 
mutations in the carboxyl terminus of erbB that 
occur during viral replication cause additional 
tumors — fibrosarcomas and angiosarcomas. We 
are studying the molecular basis for the change in 
tissue specificity of the erbB oncogene. 
The approach we are taking is to construct re- 
combinant viruses containing erbB. The advan- 
tage of this procedure is that we can undertake a 
systematic analysis of the effects of erbB muta- 
tions on the tissue specificity of tumor formation. 
The results should help explain why erbB causes 
tumors in one tissue but not in others. This infor- 
mation will be useful in designing strategies for 
clinical intervention in tumor development. 
108 
