Isolation of an Amplified DNA Sequence in Stomach Cancer

By use of the in‐gel DNA renaturation method, the presence of amplified DNA sequences was demonstrated in KATO‐III, a cell line established from a signet ring cell carcinoma of the stomach. A DNA fragment from one of these amplified regions in KATO‐III cells was cloned and designated SAM(0.2); the locus containing the SAM(0.2) fragment was referred to as SAM. The SAM locus was shown to be amplified not only in KATO‐III cells, but also in three of 24 surgical specimens of stomach cancers and in two of 13 xenografts of human stomach cancers, all of these specimens being poorly differentiated adenocarcinoma or mucinous adenocarcinoma of the stomach. The SAM locus was not amplified in 14 cell lines of cancers of other organs or in 42 surgical specimens of lung cancers.