The novel anticancer drugs irofulven and oxaliplatin are consistent and potent apoptosis inducers in tumor cells. Irofulven and oxaliplatin bind to cellular DNA as well as to protein sulfhydryls. While both DNA adducts and protein adducts are important apoptotic stimuli, the potentially lethal consequences of protein reactivity of irofulven and oxaliplatin remain understudied. The purpose of this proposal is to test the hypothesis that irofulven and oxaliplatin target key redox-controlling proteins and the subsequent distortion of the redox status of cellular proteins enhances apoptosis in cancer cells. Protein redox homeostasis is predominantly controlled by the anti-apoptotic thioredoxin (Trx) system. Trx is recognized as a potential target for therapeutic intervention, as many tumors gain growth advantage by elevating their Trx levels. Tumor cells are constantly under abnormally oxidative conditions and, therefore, may be particularly sensitive to drugs impeding the functions of Trx. Preliminary data implicate the Trx system in the effects of irofulven and oxaliplatin.
The first aim i s to investigate the binding of irofulven and oxaliplatin to Trx and other key redox regulating proteins in their purified forms and in cancer cells.
The second aim i s to determine the effects of irofulven and oxaliplatin on the functions of cellular redox proteins and the distortion of the redox status of the cell. Modulation of the global cellular redox balance will be examined in the context of the demonstrated resistance of normal cells to irofulven and oxaliplatin.
The third aim i s to establish a causative link between the targeting of the Trx system, the global distortion of protein redox status, and the induction of apoptosis by irofulven and oxaliplatin. This will include assessing the roles of redox-dependent ASK1 -mediated and AlF-mediated pathways, as well as Trx-dependent HIF-1 signaling under hypoxic conditions. The focus is on prostate cancer models, which are highly relevant to the clinical properties of these drugs. Successful completion of these aims will define the role of the Trx system as a target for irofulven and oxaliplatin, which could significantly improve the clinical use of these drugs. Ultimately, the outcomes should establish a rationale for combining targeting of redox controlling proteins with other specific anti-cancer drugs to maximize apoptosis in cancer cells that are resistant to DNA damaging agents. ? ?
