Ganglioside GM2 [GalNAcj3l-4(NeuNAccs2-3)Galf3l-4Glcj3l-lce ramide] is a major tumor-differentiation antigen in human melanoma

A human B-lymphoblastoid cell clone, L55-81, that produces human monoclonal antibody (MAb) to ganglioside G@ was established from peripheral blood B lymphocytes of a melanoma patient. L55-81 secretes IgMK light chain antibody in a serum-free medium. GM2 specificity of the antibody was tested by immune adherence assay, TLC immunostaining, and ELISA. Anti-GM2antibody was shown to have the ability to kill the GM2-rich human melanoma cell line M14 in the presence of human or rabbit complement. A purified L55-81 MAb (>99.5% purity in protein concentration) was biotinylated and tested for its reactivity to various histological-type biopsied tumor and normal tissues in an avidin-biotin detection system. L55-81 MAb (20 tag/mI) reacted with several types of tumor tissues such as melanoma (7 of 10), colon carcinoma (4 of 5), ovary carcinoma (4 of 5), breast carcinoma (1 of 5), kidney carcinoma (1 of 5), and prostate carcinoma (1 of 5). None of the normal tissues derived from 24 different organs and adjacent normal tissues surrounding the cancer ous tissues were stained. Production of the antibody in a serum-free medium, the cytotoxic potential with human complement, the inability to react to normal tissues, and the ability to target antigen-specific target cells make L55-81 a potential therapeutic agent for the treatment of cancers expressing ganglioside GM2.