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Reactive oxygen species and Genomic Instability in CML


Abstract Chronic myelogenous leukemia (CML) is a myeloproliferative stem cell disorder associated with the BCR-ABL tyrosine kinase oncogene. Genomic instability in CML is thought to ultimately cause progression of the disease and therapy-related drug resistance. The underlying molecular mechanisms that cause BCR-ABL transformed hematopoietic stem cells to be susceptible to genomic instability are unknown. Reactive oxygen species (ROS) have already been shown to generate DNA adducts and cause oxidative DNA damage, which can result in genomic mutations. A subsequent lack of appropriate repair is a major cause of genomic instability. In addition, relative levels of ROS are tightly regulated in normal hematopoiesis and are part of homeostatic mechanisms but they are chronically elevated in many cancers, including CML. We have shown that BCR-ABL regulates generation of ROS in the mitochondria through a hyperactive glucose metabolism. We propose to define signaling requirements that lead to abnormal regulation of the glycolytic pathway in BCR-ABL transformed cells, required to maintain high levels of ROS. We will use pre-clinical models of CML as well as normal and CML CD34+ stem cells. The main hypothesis to be tested is that hyperactive glucose metabolism in BCR-ABL transformed cells is sufficient for the induction of DNA damage through ROS and that targeting pathways which lead to increased glucose metabolism-dependent ROS production by BCR-ABL will ultimately decrease genomic instability. We will (1) define the molecular requirements for BCR-ABL induced oxidative DNA damage; (2) define abnormalities in signaling pathways in BCR-ABL transformed cells, regulated through the autophosphorylation site Tyr177 in BCR-ABL; (3) determine the efficacy of targeted approaches for the prevention of DNA mutations and the induction of imatinib resistance. Understanding the causes and consequences of ROS production in leukemia are likely to lead to the identification of novel therapeutic targets in the disease and may help to overcome drug-resistance. It is anticipated that these results will also improve the understanding of the role of ROS in leukemic transformation, as well as in normal hematopoietic signaling. Our results will also have relevance to others cancers, since elevated ROS and genomic instability are common among transformed cells. Project Narrative Chronic myelogenous leukemia (CML) is a hematopoietic stem cell disease caused by the BCR-ABL oncogene. Transformation by BCR-ABL is associated with a hyperactive glucose metabolism, increased reactive oxygen species (ROS) production and genomic instability. This proposal aims to evaluate the role of these unique phenomena in oxidative DNA damage and genomic mutations, ultimately leading to a better understanding of the biology of CML.

Funded by the NIH National Center for Advancing Translational Sciences through its Clinical and Translational Science Awards Program, grant number UL1TR002541.