The incidence and association with 10-year survival of amplification in five protooncogenes or transforming genes were retrospectively examined using DNAs extracted from formalin-fixed, paraffin-embedded blocks of tissues obtained from 176 consecutive patients surgically treated for primary breast carcinoma. The incidences of greater than threefold amplification of hst-1, int-2, c-erbB-2, ear-1 (one of c-erbA), and c-myc were 12, 13, 16, 10, and 4.0%, respectively. hst-1 and int-2 were almost always coamplified (21/22), while c-erbB-2 and ear-1 were frequently coamplified (18/28) with almost the same copy number. The hst-1 and int-2 pair and the c-erbB-2 and ear-1 pair, localized on chromosomes 11q13 and 17q21–22, respectively, in normal cells, were inferred to be constituents of different amplification units. Amplification of hst-1 and/or int-2 was detected preferentially in the younger age group, and was correlated with poorer prognosis in cases carrying four or more copies of the genes. Amplification of c-erbB-2 and/or ear-1 was strongly correlated with poor prognosis in all 176 patients, especially those with lymph node metastasis. Amplification of c-myc was also correlated with poor prognosis. Cox's life-table regression analysis showed that amplification of c-erbB-2 had a prognostic value, which was independent of other known prognostic factors such as lymph node status and tumor size.

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This study was supported in part by a Grant-in-Aid from the Ministry of Health and Welfare for the Comprehensive Ten-year Strategy for Cancer Control, Japan, and by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan.

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