Grant: Collaborative Health Research Projects (NSERC partnered)

A large number of histone deacetylase inhibitors (HDACi) have rapidly advanced through clinical trials for therapy of many different types of cancers. It is paramount to assess the potentially harmful side effects that the systemic use of HDACi may have on normal cells. Moreover, HDACi have thus far proven relatively ineffective in the treatment of solid tumours. For these reasons, a more extensive knowledge of the cellular pathways affected by HDACi is mandatory for these agents to achieve their full therapeutic potential. The goal of this research project is to investigate whether a small subset of biomedically relevant HDACi interfere with a major histone metabolic pathway: the deacetylation of newly synthesized histones that occurs following their genome-wide deposition onto replicating DNA. First, we will exploit state-of-the-art mass spectrometry tools developed in our laboratory (data mining, ion mobility and ion profiling strategies) to establish a repertoire of the sites of acetylation of new histones prior to their incorporation into chromatin. Second, we will label newly synthesized histones with amino acids containing stable isotopes in normal and cancer cells that progress synchronously through S-phase. Combined with mass spectrometry, this experimental strategy will enable us to determine whether clinically relevant HDACi interfere with new histone deacetylation. This is an important issue because failure to deacetylate new histones causes genomic instability, spontaneous DNA damage and strongly sensitizes cells to conventional chemotherapeutic agents that kill cancer cells by damaging DNA. Based on this, it is conceivable that combination therapy performed with HDACi and genotoxic agents may enhance eradication of solid tumours. Lastly, we will identify the enzymes that directly deacetylate specific residues in newly synthesized histones using a combination of in vivo RNA interference and in vitro HDAC assays. We anticipate that the information gathered through this project will help improve the clinical use of existing HDACi and facilitate the development of novel HDACi that are pathway- or enzyme-specific.