Amplification of the proto-oncogenes c-myc, c-erbB2, c-K-ras2, c-H-ras1, c-erbA1, c-int2 and c-fms was studied by Southern-blot analysis of DNA extracted from 27 primary ovarian carcinomas. In addition, karyotype analysis and interphase cytogenetics using fluorescence in situ hybridization (FISH) were applied to control the chromosomal variability of the tumors. By these additional analyses the possibility of a false estimation of the grades of amplification should be diminished. In nearly 50% of the studied tumors a low to moderate (2- to 10-fold) amplification of one or more oncogenes was detected. The proto-oncogene amplified most frequently was c-myc (11 tumors), followed by c-erbB2 and c-Kras2 (3 tumors each), c-fms (2 tumors), and c-int2 (1 tumor). Neither an amplification of c-erbA1 nor of c-H-ras1 could be detected in any of the tumors. Some of the tumors showed a simultaneous amplification of two or three oncogenes. The pattern of proto-oncogene amplification clearly differentiates the studied ovarian cancers from breast tumors, but also differs from some previous results obtained from ovarian carcinomas.

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