Characterization of a putative ovarian oncogene, elongation factor 1alpha, isolated by panning a synthetic phage display single-chain variable fragment library with cultured human ovarian cancer cells.

PURPOSE: In an effort to identify cell surface targets and single short-chain antibody (scFv) for ovarian cancer therapy, we used a phage display approach to isolate an antibody with high reactivity against ovarian cancer. EXPERIMENTAL DESIGN: A phage scFv library was subjected to panning against human SK-OV-3 ovarian cancer cells. A clone with high reactivity was selected and tested in immunoperoxidase staining on a panel of normal tissues and ovarian carcinoma. Using immunoprecipitation, a differentially expressed band was analyzed by mass spectrometry. The antigen subclass was characterized with reverse transcription-PCR on cDNA library of normal tissues, and 91 ovarian cancer specimens, and correlated with clinicohistopathologic characteristics. RESULTS: Ninety-six individual scFv clones were screened in ELISA following panning. scFv F7 revealed high reactivity with ovarian cancer cell lines and showed intense staining of 15 fresh ovarian cancer specimens and no staining of a panel of normal tissues. A 40-kDa protein was identified to be translation elongation factor 1alpha1 (EEF1A1; P < 0.05). The expression of EEF1A2, a highly homologous and functionally similar oncogene, was found to be restricted only to the normal tissues of the heart, brain, and skeletal muscle. Aberrant EEF1A2 mRNA expression was found in 21 of 91 (23%) of ovarian cancer specimens and significantly correlated with increased likelihood of recurrence (P = 0.021). CONCLUSIONS: scFv F7 may represent an ovarian cancer-specific antibody against translation EEF1A family of translational factors. We propose that EEF1A2 may be a useful target for therapy of human ovarian cancer.