Short-chain fatty acid inhibitors of histone deacetylases: promising anticancer therapeutics?

Cancer is a disease in which cellular growth regulatory networks are disrupted. Lesions in well-characterized oncogenes and tumor suppressors often contribute to the dysregulation, but recent work has also uncovered the fundamental importance of enzymes that modulate the acetylation status of chromatin to the initiation or progression of cancer. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are known to be involved in physiological cellular processes, such as transcription, cell cycle progression, gene silencing, differentiation, DNA replication, and genotoxic responses, but they are also increasingly being implicated in tumorigenesis. Butyrate is a short-chain fatty acid (SCFA) that acts as a HDAC inhibitor and is being clinically evaluated as an anti-neoplastic therapeutic, primarily because of its ability to impose cell cycle arrest, differentiation, and/or apoptosis in many tumor cell types, and its favorable safety profile in humans. Additionally, HDAC inhibitors could be used in combination with certain established antitumor therapeutics, such as those that target transcription, to augment clinical efficacy, and/or reduce toxicity. The molecular pathways of butyrate and related next-generation synthetic SCFAs in mediating these effects have not been fully elucidated, but HDAC inhibition is associated with regulation of critical cell cycle regulators, such as cyclin D, p21(CIP1/WAF1), and p27(KIP1). It is anticipated that a better understanding of this critical intersection between SCFAs, HDACs, and cell cycle control will lead to the design of novel treatment strategies for neoplasias. This review will summarize some of the recent research in these arenas of HDAC-directed cancer therapy and discuss the potential application of these agents in synergy with current chemotherapeutics.