While paracrine and autocrine-acting cytokines and growth factors are attractive targets for cancer therapies, few have proven indispensable for tumor growth in vivo.  A notable exception to this is the family of ligands that signal through the epidermal growth factor receptor (EGF-R).  The EGF-R is now the target of several promising clinical trials aimed at diminishing the growth and malignancy of many human cancers.  EGF-R ligands are thought to contribute to malignant disease processes by activating signaling pathways that facilitate cyclin D1 expression, cyclin-dependent kinase 4 or 6 (Cdk4/6) activation and, ultimately, retinoblastoma (Rb) inactivation.  We recently discovered that the pro-inflammatory cytokine migration inhibitory factor (MIF) is both necessary and sufficient for mitogen and oncogene-induced cyclin D1 transcription, Cdk4 activity and Rb inactivation.  Moreover, our results reveal that MIF is strongly induced by tumor promoting oncogenes and cells from MIF-deficient mice are resistant to oncogene-induced malignant transformation.  Finally, our preliminary studies find that MIF^-/- mice are strongly resistant to carcinogen-induced tumor development.  Unlike other tumor promoting cytokines and growth factors, MIF has been shown to possess a non-physiologic enzymatic activity that is evolutionarily well conserved.  We recently generated three independent classes of MIF inhibitors designed to target the substrate binding/active site of MIF.  Functional analyses of these compounds reveal that all three structures serve as potent antagonists of MIF-specific biologic processes.  We hypothesize that, through structure-based drug design and virtual combinatorial library screening, we will identify several novel, structurally distinct, and clinically viable antagonists of MIF.  It is hoped that this work will contribute to the development of a new class or classes of structure-based, rationally designed anti-neoplastic compounds.  To fulfill the stated objectives of this application, the following Specific Aims are proposed:  1) Identify novel structural analogs of small molecule inhibitors of MIF’s catalytic and bioactive properties; 2)Screen and assess the catalytic and biologic inhibitory activities of candidate MIF antagonists identified in Specific Aim 1, and; 3) Test candidate MIF antagonists in neoplastic-associated, in vivo disease models known to be potentiated by MIF actions.