The word ‘sirtuin’ (SIR) stands for Silent Information Regulator. SIRT1 is the most studied mammalian sirtuin and predominantly localises to the nucleus. Many sirtuins targets are involved in cancer and in many types of cancers, SIRT1 is found to be overexpressed. Recent observations support SIRT1 being both an oncogene and a tumour suppressor, depending on the cancer etiology and type of tissue. To answer the question “How can sirtuins function as both oncogenes and tumour suppressors?” we propose to develop highly selective ligands and study in a range of cancer cell lines the modulated activity of SIRT1. Aptamers are a novel and particularly interesting targeting modality, with a unique ability to bind to a variety of targets including proteins, peptides, enzymes, antibodies and various cell surface receptors. Aptamers are single stranded oligonucleotides that vary in size between 25 and 50 bases long and are derived from combinatorial libraries through selective targeting. They offer unique benefits compared to other targeting agents, in that they bind with high affinity and selectivity, are not immunogenic or toxic and have good clearance from the system, are easily and quickly synthesised using in vitro techniques, and are stable and consistent. The SELEX methodology is based on the idea of following an evolutionary process of selection, partition and amplification rounds to generate nucleic acids as therapeutic reagents. Since DNA molecules adopt stable and intricately folded three dimensional shapes, they are capable of providing a scaffold for the interaction with functional side groups of a ligand.
To test the above hypothesis we plan to follow the specific methodological approaches:
• Identification of aptamers against SIRT1.
• Characterisation of the interactions between selected aptamers and SIRT1 in vitro.
• Characterisation of the interactions between selected aptamers and SIRT1 in a range
of cancer cell lines.
• Development of organic ligands against SIRT1and their comparison with aptamers.