The Modulation of Retinol and Lipid Binding Proteins to enhance cell death in Ewing’s Sarcoma Family of Tumours

Abstract

There have been few advances in treatment for patients with tumours belonging to the Ewing’s Sarcoma Family of Tumours (ESFT) in the past three decades. Currently just 1 in 5 young people with metastatic disease survive to 5 years, and 1 in 10 who appear to do well initially, face the grim prospect of late relapse up to 20 years after so-called cure. Combined with significant treatment related morbidity these figures emphasise the need for more effective treatments with minimal toxicity. Fenretinide is a chemotherapeutic that has cytotoxic effects in several cancers, making it an attractive potential therapeutic. However, its use in clinical practice has been limited by poor solubility and bioavailability. I have hypothesised that this may be overcome by modulating extra- and intra-cellular binding proteins including Retinol Binding Protein 4 (RBP4) and the intra-lipid binding proteins (iLBPs) to increase the amount of fenretinide delivered to the cell. In this thesis, I have investigated the binding relationships between candidate carrier proteins and fenretinide or fenretinide-like molecules using in silico modelling and surface plasmon resonance.
Using this approach, I have confirmed that RBP4 binds to fenretinide consistent with its role as a chaperone protein for this interesting compound. Cellular Retinol Binding Proteins (I and IV) do not bind fenretinide and therefore are not candidate intracellular transporters of retinamides. Interestingly CRBP-IV may predict poor outcome in some patients. Cellular Retinoic Acid Binding Protein 2 and Fatty Acid Binding Protein 5 remain interesting candidate chaperone proteins for fenretinide and its derivatives. CRBPs (II and III) were not detected in ESFT. In silico consensus modelling alone was of limited value to predict protein-binding partners for fenretinide and its analogues. However, the combination of in silico modelling using the permissive eHiTS programme followed by surface plasmon resonance may be a useful preclinical tool to identify potential carrier proteins of retinamides including fenretinide.