The expression of epidermal growth factor (EGF) receptor was examined immunohistochemically in a total of 122 gastric and 61 colonic carcinomas, out of which 16 gastric and 8 colonic carcinomas were also examined by 125I-labeled EGF binding analysis and Western blotting. The values of EGF binding were 12.68 ± 1.98 (SE; n = 16) fmol/mg protein in gastric carcinomas and 5.72 ± 2.15 (n = 8) fmol/mg protein in nonneoplastic gastric mucosa, the difference being significant (P < 0.01). In the colonic tissue, the binding capacities in carcinomas and nonneoplastic mucosa were 13.29 ± 4.17 (n = 8) and 10.68 ± 0.41 (n = 3) fmol/mg protein, respectively. Scatchard analysis of 125I-labeled EGF binding indicated a single class of receptors in gastric and colonic carcinomas with an apparent Kd value of from 111 to 277 (n = 4) and from 87.4 to 341 fm (n = 5), respectively, except for one gastric carcinoma having two classes of receptors (Kd = 15.9 and 896 fm). In Western blotting using monoclonal anti-EGF receptor antibody, various levels of EGF receptor expression were detected in 12 (85.7%) of the 14 gastric carcinomas and in 7 (87.5%) of the 8 colonic carcinomas. Immunohistochemically, EGF receptor immunoreactivity was detected in one (3.8%) of the 26 early gastric carcinomas, while it was observed in 33 (34.4%) of the 96 advanced gastric carcinomas, the incidence between the two being significantly different (P < 0.01). In the colonic carcinomas, 47 (77.1%) of the 61 cases showed positive immunoreactivity to EGF receptor, which did not differ by histological type.

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Supported in part by a Grant-in-Aid for Cancer Research from the Ministry of Health and Welfare for a Comprehensive 10-Year Strategy for Cancer Control, Japan.

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