We are studying the mechanism by which tumor necrosis factor regulates growth and metabolism of human breast cancer cells. We found that TNF has significant antiestrogenic properties against hormone-dependent breast cancer cells in vitro. TNF blocks estrogen stimulation of growth in a time and dose-dependent manner, and blocks estrogen stimulation of cell cycle progression into the S phase. TNF downregulates the estrogen receptor and upregulates the progesterone receptor at a posttranscriptional level, suggesting its antiestrogenic effects may not be mediated through the ER. Because transforming growth factor beta (TGFbeta) is an important mediator of other antiestrogens (e.g. tamoxifen), we studied TNF modulation of TGFbeta secretion. We found that TNF increases secretion of both active and latent forms of TGFbeta in a time and dose-dependent manner in breast cancer cells. Increased TGFbeta secretion is not due to cell death, release of stored TGFbeta intracellular pools, or stabilization of extracellular TGFbeta. TNF alters the type of isomer secreted by these cells from TGFbeta1,2 to TGFbeta2. We demonstrated that these breast cancer cells secrete multiple molecular weight species of TGFbeta, that these multiple forms are biologically active, and that this pattern is not modified by TNF. TNF does not alter the transcriptional activity for TGFbeta1, TGFbeta2, TGFbeta3, and does not alter secretion of the mitogenic growth factor IGF-1. We have also developed a method for the establishment of short term cell lines from solid tumors of patients with breast cancer. We have established cell lines from the primary solid tumors or axillary lymph node metastastes of 23 patients. The cell lines are malignant cytologically and by keratin staining, and overexpress DF3 breast carcinoma antigen. Three cell lines were passaged in nude mice and then reestablished in cell culture in vitro. Karyotypic analysis of one cell line grown in nude mice demonstrates chromosomal abnormalities before and after passage in nude mice. Four cell lines have been stably transfected with a retroviral vector for TNF and secrete high levels of TNF. These cell lines can provide an in vitro and in vivo model system to study metabolic regulation of cytokines on breast cancer cells and their effects on genetic abnormalities, including oncogenes, tumor suppressor genes, and MDR genes associated with this type of malignancy.
