The transmembrane receptor encoded by the HER-2 cellular oncogene is amplif
ied in several types of human carcinomas and provides an attractive therape
utic target. Shown by immunohistology, <25% of newly diagnosed ovarian carc
inomas express the HER-2 protein. However, now we report that this protein
was expressed in all 20 tumor cell lines derived from stage III and IV ovar
ian cancers as well as in tumor cells harvested from patients with malignan
t ascites and in tumor samples taken at a second surgery, suggesting that c
ells with excess expression may have a selective growth advantage. HER-2-po
sitive ovarian carcinoma cells were shown to be sensitive to antibody-depen
dent cellular cytotoxicity, and their in vitro proliferation was inhibited
by anti-HER-2 MAb Herceptin. We postulate, therefore, that therapy which ta
rgets HER-2 may be more efficacious in patients with ovarian carcinoma than
indicated by the commonly low expression of HER-2 in tumors removed at the
time of primary surgery.