Recent studies in the PI's laboratory have defined a novel mitochondrial respiratory stress signaling, which is initiated when mitochondrial membrane potential (??m) is disrupted either by mtDNA depletion or by inhibitors of respiratory complexes. The stress signaling is initiated through increased free Ca2+, and activation of calcineurin and culminates in the activation of PKC, NFkB, C/EBP?, CREB and NFAT and altered expression of <100 genes. Stress mediated transcription activation involves hnRNPA2 as a common transcription co-activator. Research during the current grant period has provided exciting leads on a new pathway in which respiratory damage trigger cell invasion and metastasis in non-invasive cancer cells. The objective of this competing renewal application is to continue ongoing studies on mechanisms of stress-induced phenotypic changes, tumor progression, and to characterize the distinctive nature of this mitochondrial respiratory stress signaling as follows: 1) To identify the distinctive features of respiratory stress-induced NFkB activation and determine the structural/functional features of IkB?and cRel in the signal propagation. We will continue to define the distinctive structural and functional features of cRel in DNA binding and transcription activation and specificity of cRel and IkB? interaction in the signal propagation and invasiveness. 2) To determine the role of hnRNPA2 in mitochondrial stress induced transcription regulation. Results show that stress mediated transcription activation requires hnRNPA2, a common transcription co-activator that functionally synergizes the activity of promoter bound cRel/p50, C/EBP?, CREB and NFAT transcription factors. As we have found that hnRNPA2 has histone acetyl transferase activity (HAT), we will further characterize its role in the assembly of the enhanceosome through chromatin remodeling The role of HAT activity in signal propagation, and tumor progression will be studied. 3) To determine the role of respiratory stress mediated Akt activation on IkB? and hnRNPA2 function and transcription activation: Mitochondrial stress induces glucose uptake and Akt activation. The role of stress signaling in Akt activation and its effects on cRel and hnRNPA2 functions, and its HAT activity will be characterized. 4) To study the role of altered mtDNA contents and mitochondrial dysfunction in tumor invasiveness and disease progression in human cancers. We will initiate studies on the effect of mitochondrial dysfunction and respiratory stress in tumor invasiveness in human tumors. The role of mitochondrial stress in invasiveness will be further ascertained by IkB? and hnRNPA2 mRNA silencing in vivo in xenografted cells. Tumor cell lines with defined genetic background and variable tumorigenic potential as well as those engineered to express various oncogenes will be tested for the effects of mitochondrial stress on tumorigenecity and invasiveness.
The overall objective of this research is to determine how mitochondrial dysfunction either due to mutations, drug induced damage to mitochondrial DNA or membrane system initiates a stress signaling causing a global change in gene expression, cellular morphology and induces invasiveness in otherwise non invasive tumors. One aim is to characterize specific mechanisms of this stress signaling pathway for developing molecular probes that would disrupt stress signaling and stress induced pathophysiological changes in vivo and in vitro. Another major aim is to determine the physiological significance of stress signaling in human cancer by testing a panel of over 200 human esophageal, colorectal, pancreatic and liver cancers with defined genetic background and develop molecular reagents to retard the stress induced tumor progression.
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