Characterization of metabolic gene targets in response to chromosomal instability

Abstract

CIN is frequently present in advanced tumours and associated with tumorigenesis and poor clinical outcomes. CIN is thought to contribute to the development of resistance against anti-cancer drugs. CIN is specific to cancer cells, so our lab is exploiting the idea of targeting CIN itself in order to develop novel therapies that kill CIN cells. We have developed Drosophila melanogaster induced-CIN models for in vivo screening and characterization and used RNAi lines to knock down candidates in a CIN background (Chapter 2). From our screening of phosphatase and kinase knockdowns that kill CIN cells, we identified some interesting metabolic candidates that caused lethality via apoptosis in CIN background. These metabolic changes generate elevated ROS levels, DNA damage, mitochondrial hyperactivity in CIN background, showing CIN cells are sensitive to redox stress. Subsequently, we investigated the effect of these metabolic candidates in our Drosophila tumour model and found a gluconeogenic protein, PEPCK, needed for proliferation of CIN tumours. PEPCK deficiency supressed the tumour growth by increasing the cytoplasmic NADH and ROS levels. Our data demonstrated that in PEPCK deficient tumours, the glycerol-3-phosphate shuttle produced high levels of ROS. High NADH and ROS production stopped the tumour growth (Chapter 3). We also found that the purine biosynthesis pathway is needed to tolerate CIN. Depletion of nucleotide synthesis candidates altered the level of adenine nucleotides which led to DNA damage which in turn activated PARP for DNA repair, further depleting ATP levels. We found increased numbers of lysosomes in nucleotide deficient CIN cells and if their formation was blocked, CIN cells died, which suggested that autophagy is activated and required for CIN cell survival (Chapter 4). In conclusion, our findings reveal that CIN is sensitive to metabolic aberrations. Several metabolic pathways including glycolysis, gluconeogenesis and nucleotide biosynthesis pathways are activated in response to CIN. Increasing understanding of these pathways that make CIN cell survive or die may ultimately allow the design of cancer-specific drug targets for cancer therapy.