Human carcinoma cells synthesize and secrete tenascin in vitro

Tenascin is an extracellular matrix glycoprotein produced in response to epithelial-mesenchymal interactions that initiate fetal organogenesis, and it is also found in the stroma of benign and malignant neoplasms. Thirty-five human cell lines representing a variety of cancers were examined by immunoprecipitation and polyacrylamide gel electrophoresis of radiolabeled tenascin proteins from conditioned media. Two forms of tenascin with relative molecular masses of 190,000 and 250,000 were identified. Eight cell lines produced both forms. With the exception of myeloid and lymphoid leukemias and Burkitt's lymphoma, all of the mesodermal and neuroectodermal tumor lines were found to synthesize tenascin. Unexpectedly, tenascin was secreted by several mammary and colonic adenocarcinomas as well as by a line derived from normal mammary epithelial cells, and in some cases increased production was induced by transforming growth factor beta in serum-free medium. Cells producing fibronectin but not tenascin attached and spread on plastic culture dishes, while those producing tenascin alone remained suspended in the medium or were rarely attached. Tenascin also inhibited fibronectin-mediated adhesion of MCF7 breast carcinoma cells in vitro. The results suggest that tenascins synthesized and secreted by some cancer cells, especially those of epithelial origin, may have specific roles in determining tumor cell adhesion and ultimately the ability to form invasive outgrowths.

Human tumor and normal tissue reactivity of the anti-(breast cancer) monoclonal antibody BA-Br-3 and its similarity to the anti-(epithelial membrane antigen) monoclonal antibody E29

A mouse monoclonal antibody (BA-Br-3) raised against the breast carcinoma cell line CAMA-1 was previously shown to react with a greater than or equal to 300-kDa globule-like glycoprotein from human milk fat also expressed in the cytoplasm and on the surface of human carcinoma cells of different histological types. In this report the reactivity of this mAb with a large number of normal and malignant human tissues was analyzed using immunoperoxidase techniques. When tested on sections of both fresh-frozen tissues and formalin-fixed, paraffin-embedded tissues, BA-Br-3 reacted with a formalin-resistant antigenic determinant expressed by normal and malignant epithelial cells. Preferential reactivity was observed at the apical portion of ductal epithelial cells in normal breast and in glandular epithelia distributed in several other organs. Reactivity with mucin-like secretions in the lumina of ducts was also found. BA-Br-3 reacted mostly in heterogenous staining patterns with 88% of 49 breast carcinoma specimens tested, regardless of their histological type or whether they were primary or secondary neoplasms. Testing of epithelial malignant tumors other than breast carcinomas with this antibody showed that 127 of 151 (84%) were also reactive. mAb BA-Br-3 and E29 (a commercially available anti-(epithelial membrane antigen) shared very similar staining patterns and distributions of reactivity with breast and other epithelial tumors. However, BA-Br-3 showed a significantly higher percentage of reactivity with melanoma (33% versus 6%, P = 0.003) and a trend toward a higher percentage of reactivity with sarcoma (55% versus 27%, P greater than 0.05). This antibody, therefore, defines a molecule that is a member of the mucin-like epithelial membrane antigen family. Further studies are warranted to determine its usefulness in antibody-directed cancer diagnosis, prognosis, and immunotherapy.