Our laboratory has developed a completely new approach to generating an anticancer vaccine. Using a free solution isoelectric focusing (FS-IEF) technique we can efficiently enrich for multiple chaperone complexes from tumor lysates. It has been documented that vaccination with these chaperone rich cell lysates (CRCL) is more effective than immunization with purified individual chaperones (heat shock proteins, HSPs). The antigenicity of CRCL can be augmented further by loading them onto dendritic cells (DCs) resulting in protection against murine tumors even in the setting of pre-existing disease. In addition to their antigen carrying capacities, CRCL have potent immunostimulatory effects on DCs. As adjuvants CRCL provide danger signals enhancing the immunogenicity of leukemia cells undergoing apoptosis following drug treatment. Chronic Myelogenous Leukemia (CML) is a useful model for the study of antigen specific immune responses to peptides chaperoned by CRCL. It is unique among leukemias in that the bcr-abl oncogene itself is a tumor antigen. Moreover, CML cells express other potential target antigens such as Proteinase-3 and Wilms' tumor protein (WT1). The goal of this proposal is to generate sufficiently strong pre-clinical data to move CRCL vaccines into the clinical setting. Our laboratory intends to continue studies in the 12B1 murine CML model in order to understand further the mechanisms of action of CRCL vaccines. In parallel, in vitro studies will examine the effects of human CML-derived CRCL on human cells in order to establish efficacy and safety. The following specific aims are proposed. 1) Characterize the peptide antigen repertoire of CRCL vaccine derived from 12B1 murine leukemia. 2) Study the in vivo synergistic effects of combining CRCL vaccine/adjuvant with STI-571, a tyrosine kinase inhibitor that induces apoptosis in murine 12B1 bcr-abl+ cells. 3) Biochemically characterize human CML-derived CRCL. 4) Evaluate the effects of human CML-derived CRCL on human DCs and examine the potential of CRCL-pulsed DCs to generate leukemia specific CTLs. The successful completion of these aims may result in the use of CRCL as an effective vaccine against CML, a disease in which immunotherapy has already shown promise.