Production of anti-tumor human monoclonal antibodies using different approaches

The production of anti-tumor human monoclonal antibodies (MAbs) by human-human or human-mouse hybridoma technology was studied. UC729-6, a human lymphoblastoid cell line, or NS-l, a mouse myeloma cell line, were fused with lymphocytes isolated from regional lymph nodes of 26 patients with breast or gastrointestinal cancer, resulting in 130 immunoglobulin-secreting human-human hybrids and 21 human-mouse hybrids. The supernatants of 88 hybrids were screened against a panel of cancer cells. The supernatants of 37 human-human hybrids and 2 human-mouse hybrids reacted with cancer cell lines. After three times subcloning, only one anti-breast cancer hybrid human MAb, IgG(λ) human-human hybridoma (MUBL-6), and one anti–gastric cancer human MAb, IgM(λ) human-mouse hybridoma (HMG-1), were obtained. The antibody-secreting level was 1–4 μg/ml/24 h.

Production of anti-breast cancer human MAbs by Epstein-Barr virus (EBV) hybridoma was also studied. Human lymphocytes were derived from draining lymph nodes of a breast cancer patient, whose serum antibody strongly reacted with tumor associated antigen (TAA). The enriched B cells were transformed with EBV in vitro. Positive antibody-secreting B cells were selected, expanded, and fused with heteromyeloma SHMD-33. The fusion frequency was 28/10⁷ lymphocytes. Among them were 16 hybridomas secreting human immunoglobulin. After subcloning, 60% of the cloned hybridomas kept their antibody-secreting ability. Six observed hybridomas remained stable for more than 1 year in tissue cultures. The antibody-secreting level was 2.9–30 μg/ml/24 h. Supernatants from these hybridomas all reacted with breast cancer cell lines but not with gastric cancer cell lines. The supernatants from these hybridomas reacted with malignant cells in some breast cancer tissue sections but not with stroma or normal cells. In summary, the EBV hybridoma technique offers several advantages over other hybridoma systems for generating anti-tumor human MAbs.