My laboratory is studying the hormonal and cytokine regulation of normal breast epithelium and breast cancer cell growth and metabolism. The goal of these studies is to define the mechanism of action of chemopreventive agents, and to develop new treatment strategies for the chemoprevention of breast cancer. A method has been developed for the establishment of short- term cell lines from normal breast tissue, and from solid tumors of patients with breast cancer. Studies have demonstrated that all-trans (AT) and 9-cis (9C) retinoic acid inhibit growth of normal mammary epithelial cells in a time- and dose-dependent manner. All normal mammary cell lines expressed the gene for the retinoic acid receptors RAR beta, gamma and RXR alpha, beta, gamma as determined by RT-PCR. AT and 9C act additively with both tamoxifen and interleukin-1 (IL-1) to inhibit growth of human breast cancer cells in culture in a time- and dose-dependent manner. All four agents block cell cycle progression at GOG1. AT, 9C, tamoxifen, and IL-1 individually induce apoptosis in breast cancer cells as studied by 3H- thymidine release or DNA fragmentation. AT, 9C, and IL-1 act additively with tamoxifen to enhance apoptosis. These findings indicate new targets for the treatment of breast cancer, and provide important background for two ongoing trials, one evaluating retinoids and tamoxifen in the chemoprevention of breast cancer, and a second evaluating breast cell lines from women at high risk for breast cancer. Three tumor cell lines have been passaged in nude mice and reestablished in culture. All short term breast tumor cell cultures constitutively express class I antigen. IFN-gamma in vitro increased class II antigen, tumor associated DF3 antigen, and intercellular adhesion molecule 1 (ICAM-1). The ability to maintain and upregulate HLA and tumor associated antigens may play an important role in both immunolocalization and immunotherapy of these tumors. The cytokine TNFalpha is a potent growth inhibitor of breast cancer cells. TNFalpha dramatically and rapidly increased secretion of the negative growth factor TGFbeta. TNFalpha increased secretion of both latent and active forms of TGFbeta, and this correlated with degree of growth inhibition by TNF. TNF shifted the type of isomeric secretion of these cells from TGFbeta1.2 to TGFbeta2. The secreted TGFbeta has been characterized by immunoblotting and gel filtration analysis. Increased TGFbeta secretion by TNF appears to be due to a posttranscriptional mechanism. Modulation of TGFbeta by TNF indicates an important regulatory site, and may allow a wide range of autocrine, paracrine or endocrine effects on tumor growth.
