Inhibiting The Master Regulator, Heat Shock Transcription Factor (Hsf1) Using A Potent Rna Aptamer In Drosophila Melanogaster and Human Cancer Cells

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: All organisms have a well-conserved heat shock response that is universal among species as diverse as bacteria, plants, and animals. Upon heat stress, the heat shock transcription factor (HSF1) orchestrates the expression of molecular chaperones that allow the organism to cope with the cellular damage induced by the stress. Interestingly, these molecular chaperones, or heat shock proteins, are amongst the most highly conserved proteins throughout bacteria, animal and plant kingdoms. Because a high concentrations of damaged proteins is deleterious to cells, the heat shock response has become an integral survival response of living systems, one that rapidly evolving systems like cancer cells utilize quite efficiently. Therefore, to further understand genetic instability disorders like cancer, and at the same time to broaden the identification of novel drug targets, we must first be capable of efficiently disrupting the chaperone-buffering system that maintains cancer cell survival. Recently, HSF1 has been found to promote cellular transformation in mammals. My studies focus on the role of HSF1 in animal development and maintenance of the transformed phenotype using a highly-specific RNA aptamer (iaRNAHSF) that binds to yeast, Drosophila, and mammalian HSF1. In Drosophila, the expression of iaRNAHSF reduces normal expression of the Hsp83 chaperone and induces developmental abnormalities that mimic the spectrum of phenotypes previously reported when Hsp83 activity is reduced. Using Drosophila mutants as a model for tumorigenesis, I found that HSF1 inhibition with iaRNAHSF effectively suppresses the abnormal growth phenotypes induced by constitutively active EGF receptor (EGFR) and Raf oncogene that normally function as part of the Hsp83-regulated cell survival pathway. Moreover, HSF1 inhibition by this same iaRNAHSF in various human cancer lines resulted in the reduction of molecular chaperones that normally promote cell survival, thereby triggering apoptosis. Collectively my studies demonstrate the potent application(s) of the RNA aptamer technology in investigating transcription regulation and cancer biology, as well as in testing of putative drug targets in vivo.
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