Ο ρόλος του υποξικού παράγοντα στην ανοσοφλεγμονώδη και αγγειογενετική ρύθμιση του καρκίνου

Abstract

Patients with Von Hippel-Lindau (VHL) disease develop multiple, synchronous or metachronous clear cell carcinomas, hemangioblastomas of the central nervous system, pheochromocytomas and papillary cystadenomas of the pancreas, middle ear, epidydimal cyst and adnexal organs. The protein encoded by the VHL gene (pVHL) is a tumor suppressor protein that serves as the cognate receptor of an intracellular E3 ubiquitin ligase that targets proteins for ubiquitination and proteasomal degradation. The best studied substrates of pVHL are the alpha regulatory subunits of hypoxia inducible factor 1 and 2 (HIF). Preclinical experiments and human renal cell carcinoma analysis strongly suggest that regulation of HIF2a by pVHL is necessary and sufficient for suppression of renal cell carcinoma development. In this thesis we present how we developed a cell-based assay suitable for high throughput screen. We used this assay to screen a collection of small molecule chemical compounds and we discovered eight inhibitors of HIF2a activity. We then went into showing that these compounds selectively decrease HIF-2a translation in an mTOR independent manner, by enhancing the binding of Iron Regulatory Protein 1 (IRP1) to an Iron-Responsive Element (IRE) within the 5’-untranslated region (UTR) of the HIF-2a message. Knocking down the expression of IRP1 by shRNA abolished the effect of the compounds. Hypoxia de-repressed HIF-2a translation by disrupting the IRP1- HIF-2a IRE interaction. These small molecules can be used as lead structures for the development of anticancer and anti-inflammatory drugs that work via inhibition of HIF2a. In addition, the chemical biology linked to these compounds shed light into an old question of cellular physiology. It is known that cells transiently adapt to hypoxia by globally decreasing protein translation. However, specific proteins needed to respond to hypoxia evade this translational repression. The mechanisms of this phenomenon remained unclear. Our work describes a molecular mechanism by which translation of the HIF-2a message is maintained during conditions of cellular hypoxia through inhibition of IRP-1 dependent repression.