JANEUTICS - From the oncojanus function of mitochondrial genes to anti-cancer therapeutics strategies

Background Mitochondrial genes mutations are known modifiers of tumorigenesis. According to the Warburg hypothesis that a mitochondrial dysfunction may underlie the metabolic change cancer cells undergo to persist proliferation and invasiveness, a respiratory chain malfunctioning has been shown to contribute to a loop of genetic instability via reactive oxygen species, tumor growth and metastatic potential, regulated by the hypoxia-inducible factor-1a (HIF1a). Nevertheless, a severe respiratory complex I (CI) impairment has been demonstrated in low-proliferative, indolent oncocytic tumors, where the metabolic rearrangements that follow disassembly of CI prevent HIF1a stabilization, leading to the inability of cancer cells to adapt to the hypoxia. CI may therefore neither be looked at as a tumor suppressor nor as an oncogene, since its contribution to tumorigenesis may depend on the type and degree of dysfunction. Hypothesis We hypothesize that a severe CI dysfunction may hamper tumor growth, from which derives our recent functional definition of oncojanus. Disruption of mitochondrial CI would induce pseudonormoxia, preventing the tumor to acquire a Warburg phenotype and progress to malignancy. CI disruption may therefore be induced locally by targeted drugs to arrest tumor growth. Aims The overall project goal is to prove that CI may be envisioned as a lethality target for potential anti-cancer strategies by providing a detailed mechanistic explanation of the biochemical and molecular events triggered upon CI disruption in several cancer cell models. The generation and implementation of animal models will constitute anadded value that will strongly contribute to the proof of concept thatCI is a valid anti-cancer target. Subsequently, the project aims at translating into pre-clinical practice the disruption of CI as an anti-cancer strategy, by testing compounds impinging on CI function. Experimental Design The experimental design of the proposal will consist of three main tasks: - to dissect the molecular mechanisms linking CI disruption to pseudonormoxia and the latter to tumor growth arrest; - to use a well-documented Drosophila model of tumorigenesis to specifically switch off CI expression and test its effect on cell/mass behaviour; this task will set the basis for the design and realization of a transgenic conditional and inducible mouse model to prove that CI disruption induced in spontaneously generated tumors is efficient in blocking tumor progression; - to assess potential therapeutic anti-cancer pharmacological strategies aimed at disruptin CI to hinder tumor growth. Expected Results The main expected results will be: - The comprehension of the effect of CI-mediated NADH consumption and essential Krebs cycle metabolites balance on prolyl- hydroxylases activity and HIF1a stabilization. - The proof that pseudonormoxia is the main causative determinant of the observed CI disassembly-mediated decrease of tumor growth in vivo. - The demonstration of the antitumorigenic effects of localized CI disruption in tumors generated in Drosophila and, eventually/preliminarily, in transgenic mice. - The selection of compounds able to hamper CI function in vitro and in vivo as an anti-cancer pre-clinical strategy.