[Background] The use of humanized or murine/human chimeric monoclonal antibodies (MoAbs) is applied to clinical use as anticancer therapy like HER-2-specific trastuzumab (Herceptin) against breast cancer, showing increased overall survival. These antibodies are characterized as humanized or murine/human chimeric MoAbs, which will cause adverse events with immune response recognizing these antibodies as foreign bodies in patients' body. Fully human MoAb (HuMoAb) is ideal to prevent such immune response, and at the present, HuMoAb is not yet applied to clinical use. We have established a successful production of HuMoAbs, reacting specifically to cancer cells, not to normal cells, utilizing human hybridoma technique with tumor infiltrating lymphocytes (TILs) or lymphocytes derived from lymph nodes. In the present study, on the basis of reactivity to human cancer cell lines, we selected a novel clone of HuMoAb derived from lymphocytes in gastric cancer. [Materials and methods]Lymphocytes were collected from clinical specimen of a gastric carcinoma patient. Hybridomas were established using these lymphocytes and mouse myeloma cell, P3U1. After selecting hybridoma clones, which binds to cancer cells, fluorescence microscope and immunohistochemical staining were used to examine antibodies' ability to attach on cell surface of various kinds of specimen. To evaluate inhibitory effect of each antibody on cancer cell growth, human lung cancer cell line HLC-1, the human stomach cancer cell line MKN-45, and the human pancreas cancer cell line PANC-1 were examined using MTT method. Cells were incubated with 100, 50, 25, 12.5, and 6.25μg/ml of each antibodies or non-specific human antibody as a control vehicle for 6 days, followed by calculating inhibition rate compared with the control. [Results] In established antibodies, we select a clone of HuMoAb derived from gastic cancer lymphocytes which showed growth inhibition rates by this antibody which was 94% in HLC-1, 64% in MKN-45 and 55% in PANC-1, while no growth inhibition occurred in normal HUVECs. This antibody showed specific and intense reactivity not only to the cell membrane, but also to the cell nucleus of HLC-1 and HSC-3 in immunohistochemical staining. Using xenografts forming from cancer cell lines in nude mice and surgically resected clinical specimen from patients, we could demonstrate a broad spectrum of reactivity of the antibody to 3 out of 4 xenografts (75%) and 4 out of 5 clinical specimen (80%), while no reactivity of the antibody was observed in normal sites, in fluorescence microscope. [Conclusion] we successfully produced a novel HuMoAb which reacted specifically to cancer cells, inhibiting cell growth. This HuMoAb will have a potential to be utilized as an anticancer agent without causing any immunological reaction in human.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]