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-1, a mouse myeloma cell line, were fused with lymphocytes isolated from regional lymph modes 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(lambda) human-human hybridoma (MUBL-6), and one anti-gastric cancer human MAb, IgM(lambda) human-mouse hybridoma (HMG-1), were obtained. The antibody-secreting level was 1-4 micrograms/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 28/10(7) 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 micrograms/ml/24 h. Supernatants from these hybridomas all reacted with breast cancer cell lines but not with gastric cancer cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)