Description of a new monoclonal antibody, FC-2.15, reactive with human breast cancer and other human neoplasias.

FC-2.15 is an IgM monoclonal antibody (MAb) obtained by immunizing Balb/c mice with tumor epithelial cells from a human undifferentiated primary breast carcinoma. FC-2.15 reacts with 93.9% (31/33) of human breast primary tumors, independently of their histology and hormone receptor content. Moreover, FC-2.15 reacts with 79.6 +/- 13.8% (mean +/- SD) of total breast malignant tumor cells and with 88.7 +/- 9.9% of proliferating tumor cells. It recognizes other neoplasia such as colon cancer, squamous carcinoma and melanoma. Among the normal tissues examined, strong cross-reactivity was found with kidney proximal convolute tubules, bone marrow myeloid progeny, peripheral granulocytes and large bowel epithelium. Through Western blots, FC-2.15 recognizes three major bands of Mr 160 kDa, 130 kDa and 115 kDa in membrane extracts of MCF-7 cells grown in nude mice and of human breast carcinoma and three major bands of 250 kDa, 185 kDa and 105 kDa in membrane extracts of peripheral granulocytes. This MAb mediates complement- cytotoxicity against malignant cells, reducing the clonogenic capacity of breast primary tumor cells and MCF-7 cells to 35.6 +/- 41.2% and 11.7 +/- 4.8% of control values respectively, whereas that of normal bone marrow cells is not affected (104.7 +/- 17.4%).