Cytokines have potent effects controlling the proliferation, survival (anti-apoptotic), and drug resistance of a considerably diverse spectrum of tumor cells. Without doubt, the most rigorously studied cytokine which affects these biological processes in a variety of tumor cells, is the pro-inflammatory cytokine IL-6. While there is accumulating basic and clinical research data to suggest that inflammation promotes neoplasia, IL-6 may stand as a centerpiece in the process. Our studies in 2007 are summarized below. 1) We have studied the signal and molecular pathways by which IL-6 facilitates the growth and drug resistance in human myeloma cells. We identified the STAT3 pathway as a major pathway involved in the growth of these cells and have blocked this pathway by intervening with two different nuclear receptor mechanisms involving estrogen receptors and PPARg, each blocking through differing mechanisms. A large number of tumor cells, including prostate, multiple myeloma, renal cell carcinoma, hepatoma, pancreatic carcinoma, etc. secrete and respond to IL-6. The mechanisms are unknown. We have also studied molecular aspects which regulate IL-6 secretion from bone marrow stromal cells, a major source of endogenous IL-6, and are currently developing strategies to block IL-6 production either genetically or pharmacologically. 2) Development of new therapeutic strategies for the treatment of breast cancer. Based on experience in studies on the estrogen receptors (ER) in our laboratory, we have focused our research towards the development of new intervention strategies for the treatment of breast cancer at the level of ER DNA binding, rather than classical antagonism of estrogen binding. Estrogen receptors contain zinc finger motifs required for their DNA binding and transcriptional activity. We have discovered that certain electrophilic reagents covalently modify ER zinc fingers resulting in the ejection of zinc and selective inactivation of estrogen receptors. This year we have extended these finding to screen for more water soluble compounds and also tested them against Tamoxifen resistant tumor cells. A hallmark of current Tamoxifen tratment of breast tumors is that they almost always develop resistance. We have recently, discovered that our compound will, in fact, reverse the resistance of human breast cancer lines to Tamoxifen both in vitro and in vivo. 3) IL-6 regulation of epigenetic gene silencing. Among the molecular and cellular aspects IL-6 may have on promoting neoplasia, we have discovered that IL-6 may also regulate and maintain gene silencing by facilitating gene promoter CpG methylation. IL-6 was shown to silence the tumor suppressor gene p53 in a significant number of human multiple myeloma cell lines. Four genes also known to participate in DNA repair were also shown to be silenced, thus impairing the myeloma cells to repair genetic damage. Also. MnSOD was shown to be silenced by promoter methylation in human multiple myelomas and pancreatic carcinomas, disabling the management of the endogenous mutagenic effects of reactive oxygen species (ROS). Thus, epigenetic silencing may contribute to the major mutational and chromosomal damage that accumulates during the neoplastic process. 4) We have identified experimentally and validated from clinical data bases that the TGFbetaRIII, a member of the Tumor Growth Factor-Receptor family, is downregulated during the development of human prostate cancer. Experimentally, deletion of the gene by siRNA methods leads to a transformed phenotype in normal prostate epithelial cells. Also, we have developed a new bifunctional colchicnoid drug which binds to the androgen receptor and is being tested against androgen-insensitive prostate cancer cells.
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