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(Slamon et al., 1987;Varley et al., 1987), and small cell lung carcinomas (Johnson et al., 1988). Moreover, specific chromosome abnormalities have also been found in a number of human cancers (Yokota et al., 1987;Baker et al., 1989;Lee et al., 1989). However, activation of proto-oncogenes in gastric carcinomas is low compared to colonic and pancreatic carcinomas (Forrester et al., 1987;Smit et al., 1988).Loss of chromosomal heterozygosity is also infrequently found in gastric carcinomas even at chromosomal loci frequently deleted in other tumours, and little is known about genetic changes that are associated with metastasis of gastric carcinomas. We have demonstrated previously that amplification of ERBB and ERBB2 genes is detected in 2.7% and 5.4% of primary gastric carcinomas, respectively (Yoshida et al., 1989 Southern blot analysis High molecular weight DNAs were prepared using the phenol-chloroform method after treatment with sodium dodecyl sulphate (SDS) and proteinase K. DNAs were digested with EcoRI or BamHI, and 10 iLg of completely digested DNAs was electrophoresis on 0.8% agarose gel. After electrophoresis, DNAs were denatured, neutralised and transferred to nitrocellulose filters according to the method of Southern (Southern, 1975). The filters were hybridised under stringent conditions with 32P-labelled probes. After hybridisation, filters were washed and exposed to Kodak XAR-5 films. The same filters were hybridised repeatedly with probes for several oncogenes to exclude the possibility that the difference in the intensities of the bands in different lanes was due to difference in the amounts of DNAs loaded on agarose gels. The levels of amplification were determined by densitometry and the sum of the densitometric signals of all the bands was taken.Slot blot analysis DNAs were extracted from formalin-fixed and paraffinembedded tissues of 20 early gastric carcinomas and one advanced gastric carcinoma whose metastatic tumours had amplification of ERBB2, HST1, and INT2 genes. Sections of 20 Itm in thickness were cut from the blocks using a microtome and these sections were collected. DNAs were extracted following the methods of Goelz et al. (1985) or Dubeau et al. (1986). Ten ILg of the DNA was dissolved in 0.4 M sodium hydroxide, and TE (10 mM tris hydroxymethyl aminomethane and 1 mM ethylene diaminetetraacetic acid (EDTA) pH 7.4) was added to make 50 pAl of the solution. The samples were incubated for 10 minutes at 37°C, treated with an equal volume of 2 M ammonium acetate and applied to a nitrocellulose filter. Filters were baked at 80°C for 2 hours under vacuum. The procedure of hybridisation was the same as that of Southern blot analysis as described above. DNA

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