Tyrosine kinase activity of epidermal growth factor receptor in human gastric carcinomas.

We examined tyrosine kinase activity of epidermal growth factor (EGF) receptor in a total of 34 human gastric carcinomas as well as in non-neoplastic gastric mucosa from the same patients. EGF receptor kinase activity of the carcinoma tissues and the non-neoplastic mucosa were 1.28 +/- 1.00 (Mean +/- S.E.) and 0.16 +/- 0.04 respectively, if the EGF receptor kinase activity of human placenta is 10. Twenty-one (62%) carcinoma tissues showed higher EGF receptor kinase activity than corresponding non-neoplastic mucosa, while in 6 cases (18%) the kinase activity was higher in the non-neoplastic mucosa than in the tumor tissues. No obvious correlation was observed between the increased kinase activity in the tumors and histological type or tumor staging. One tumor showed extremely high receptor kinase activity with ERBB gene amplification. This tumor showed strong immunoreactivity to EGF itself.