- Metabolic stress, a hallmark of cancer, is an early event in tumorigenesis that accumulates in the cell from endogenous processes, exogenous conditions, and/or agents that induce oxidative stress. Additionally, the aberrant accumulation of reactive oxygen species (ROS), as well as altered mitochondrial metabolism (i.e., oxidative or metabolic stress), are early events in the process of cellular reprogramming that under specific conditions leads to tumor cell resistance. It has become increasingly clear that lysine acetylation (i.e., mitochondrial Acetylome) is the primary post-translational modification employed by the mitochondrial to sense changes in ROS and/or metabolic conditions and initial adaptive or reparative signaling processes, including metabolic reprogramming to maintain homeostatic poise. While a link between the dysregulation of the mitochondrial Acetylome, ROS detoxification (i.e., metabolic stress), and metabolic reprogramming leading to tumor cell resistance has long been suggested, rigorous mechanistic data to supporting this intriguing idea has been limited. In this grant application it is proposed that the acetylation status of manganese superoxide dismutase (MnSOD), a critical mitochondrial enzyme, directs detoxification activity as well as connects metabolic stress and mitochondrial reparative pathways that maintain metabolic fidelity. In this regard, it is proposed that MnSOD exhibits a dichotomous function, based on the acetylation status of K68, where the homotetrameric form acts as a protective detoxification enzyme against aberrant ROS levels. In contrast, K68 acetylation inhibits the homotetrameric complex and MnSOD subsequently forms a monomeric protein form that is proposed to function as an oncoprotein. Thus, it is proposed that the dysregulation MnSOD axis, due to acetylation, alters MnSOD function which subsequently reprograms mitochondria resulting in a tumor cell anti-cancer resistance therapy phenotype. In addition, targeted the acetylation status or restoring the MnSOD functions will be used to generate and validation of new therapeutic strategies to sensitize tumor cells to cytotoxic therapies
This research proposal addresses the question that it is becoming increasing clear that there is a dichotomous functional role for MnSOD in tumorigenesis as well as tumor cell resistance. Specifically, MnSOD appears to function as a tumor suppressor (TS) during the early, proliferative stage of tumor initiation, yet once tumorigenesis progresses, MnSOD levels appear to positively correlate or contribute to a more aggressive tumor phenotype. In this regard, it is hypothesized that the acetylation status of K68 directs whether MnSOD functions as a protective homotetrameric detoxification complex versus a monomeric peroxidase enzyme that induces HIF2? levels and induces an anti-cancer, i.e., IR and Cisplatin, tumor resistance phenotype.
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