Histone deacetylase inhibitors and the promise of epigenetic (and more) treatments for cancer

How have the data from the initial clinical trials of histone deacetylase inhibitors (HDACi) improved our understanding of how these drugs work? And what key facts do we still need to understand about the biology of HDACi? Histone deacetylases (HDACs) are considered to be among the most promising targets in drug development for cancer therapy, and first-generation histone deacetylase inhibitors (HDACi) are currently being tested in phase I/II clinical trials. A wide-ranging knowledge of the role of HDACs in tumorigenesis, and of the action of HDACi, has been achieved. However, several basic aspects are not yet fully understood. Investigating these aspects in the context of what we now understand about HDACi action both in vitro and in vivo will further improve the design of optimized clinical protocols.