(PQ9) Prevention of Bleomycin-induced Pulmonary Toxicity by Dichloroacetate (DCA)

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PROJECT SUMMARY Bleomycin has proven to be an effective chemotherapeutic agent for the treatment of various human cancers, particularly when combined with other agents, and can achieve up to 90% cure rate. However, its efficacy is significantly hampered by its serious pulmonary toxicity. 10% of cancer patients treated with bleomycin develop fatal pulmonary fibrosis. No effective therapy for pulmonary fibrosis is currently available. Bleomycin-induced pulmonary fibrosis is characterized by myofibroblastic activation, which in turn, produces excessive amounts of extracellular matrix. Hypoxia is a prominent component of severe tissue injuries, such as fibrosis, due to damaged vasculature and increased oxygen consumption from infiltrated cells with high metabolic demands. The remodeling response to hypoxia is controlled primarily by hypoxia-inducible factor-1 (HIF-1). HIF-1 signaling has been implicated in severe tissue injury and fibrosis, yet, molecular mechanisms that regulate the contributions of fibroblasts/myofibroblasts to fibrotic progression in the context of the hypoxic microenvironment are poorly understood. We sought to determine the relationship between fibroblast hypoxic signaling and the development of pulmonary fibrosis utilizing a conditional knock-out system in which the Hif-1α gene is specifically ablated in fibroblasts, the essential cells contributing to the pathogenesis of pulmonary fibrosis. Fibroblast-specific Hif-1α deletion or pharmacological inhibition of HIF-1α target, pyruvate dehydrogenase kinase1 (PDK1), a mitochondrial kinase that enhances cellular glycolytic flux by suppressing mitochondrial respiration, resulted a significant reduction of bleomycin-induced myofibroblast activation and fibrotic progression. Dichloroacetate (DCA), a PDK inhibitor, effectively suppresses fibrotic progression. These findings lead us to hypothesize that fibroblast HIF-1/PDK axis promotes the profibrotic progression by PDK-mediated glycolytic metabolic reprogramming, which can exploited as a therapeutic target against pulmonary fibrotic toxicity. To test this, Aim 1 will determine if fibroblast HIF-1/PDK-mediated glycolytic reprogramming promotes myofibroblastic activation and differentiation. Utilizing a tumor/pulmonary fibrosis model, Aim 2 will characterize potential synergistic anti-cancer activity of bleomycin and DCA, as well as, the anti-fibrotic effects of DCA. Our proposed study will specifically delineate the fibroblast hypoxic response with emphasis on HIF-1/PDK–mediated metabolic reprogramming in the fibrogenic process. This previously undescribed metabolic alteration in fibroblasts can be exploited as a novel therapeutic strategy for preventing pulmonary toxicity and fibrosis especially given that DCA has been used successfully and safely on humans with metabolic disorders for more than 30 years, and is recently being evaluated for targeting cancer metabolism, which rationalizes a facilitated clinical application for bleomycin-treated cancer patients. This study will lead to the innovative design of more effective and safer bleomycin combinational regimens in a number of human cancers by improving anti-cancer effects and preventing its fatal pulmonary side effects simultaneously.