Current Topics in Medicinal Chemistry - Volume 19, Issue 12, 2019

All the heritable alterations in gene expression and chromatin structure due to chemical modifications that do not involve changes in the primary gene nucleotide sequence are referred to as epigenetics. DNA methylation, histone modifications, and non-coding RNAs are distinct types of epigenetic inheritance. Epigenetic patterns have been linked to the developmental stages, environmental exposure, and diet. Therapeutic strategies are now being developed to target human diseases such as cancer with mutations in epigenetic regulatory genes using specific inhibitors. Within the past two decades, seven epigenetic drugs have received regulatory approval and many others show their candidature in clinical trials. The current article represents a review of epigenetic heritance, diseases connected with epigenetic alterations and regulatory approved epigenetic drugs as future medicines.

The causes and progression of cancer are controlled by epigenetic processes. The mechanisms involved in epigenetic regulation of cancer development, gene expression, and signaling pathways have been studied. Histone deacetylases (HDACs) have a major impact on chromatin remodeling and epigenetics, making their inhibitors a very interesting area of cancer research. This review comprehensively summarizes the literature regarding HDAC inhibitors (HDACis) as an anticancer treatment published in the past few years. In addition, we explain the mechanisms of their therapeutic effects on cancer. An analysis of the beneficial characteristics and drawbacks of HDACis also is presented, which will assist preclinical and clinical researchers in the design of future experiments to improve the therapeutic efficacy of these drugs and circumvent the challenges in the path of successful epigenetic therapy. Future therapeutic strategies may include a combination of HDACis and chemotherapy or other inhibitors to target multiple oncogenic signaling pathways.

Epigenetics play a key role in the origin, development and metastasis of cancer. Epigenetic processes include DNA methylation, histone acetylation, histone methylation, and histone phosphorylation, among which, histone acetylation is the most common one that plays important roles in the regulation of normal cellular processes, and is controlled by histone deacetylases (HDACs) and histone acetyltransferases (HATs). HDACs are involved in the regulation of many key cellular processes, such as DNA damage repair, cell cycle control, autophagy, metabolism, senescence and chaperone function, and can lead to oncogene activation. As a result, HDACs are considered to be an excellent target for anti-cancer therapeutics like histone deacetylase inhibitors (HDACi) which have attracted much attention in the last decade. A wide-ranging knowledge of the role of HDACs in tumorigenesis, and of the action of HDACi, has been achieved. The primary purpose of this paper is to summarize recent HDAC inhibitors and the synthetic routes as well as to discuss the direction for the future development of new HDAC inhibitors.

The occurrence and development of tumors are closely related to epigenetic instability which modulates gene expression through DNA methylation, histone modification, chromatin remodeling, and RNA-related silencing. Histone deacetylase (HDAC) and poly (ADP-ribose) polymerase (PARP) are targets of epigenetic regulation. Over the years, a large number of studies have shown that HDAC inhibitors and PARP inhibitors have synergistic effects in the treatment of tumors, and there are reports of related dual HDAC/PARP inhibitors. This review will give a brief summary of the synergistic mechanisms of HDAC inhibitors and PARP inhibitors and introduce the design of the first dual HDAC/PARP inhibitor, which may guide the design of more dual HDAC/PARP inhibitors for the treatment of tumors.

Sirtuins family is a class of NDA+ dependent protein deacetylases that play a key role in the regulation of several aspects of biological processes, such as cell cycle regulation, autophagy, immune and inflammatory response. Many studies have shown that sirtuins2 as a key player in the cancer pathway is of great significance in tumorigenesis. This review summarizes the newly discovered, in recent years, some SIRT2 inhibitors for cancer target structure, action mechanism, biological activity, substrate specificity, and signaling pathways.

Background: Neddylation is an important post-translational modification of proteins, in which a NEDD8 (neural-precursor-cell-expressed developmentally down-regulated 8) is covalently introduced onto the substrate proteins to regulate their functions and homeostasis. As neddylation is frequently up-regulated in various cancers, its interference was proposed as a promising therapy of related diseases. Objective: The recent advances in developing neddylation interfering agents were summarized to provide an overview of current achievements and perspectives for future development. Methods: Reports on neddylation interfering agents were acquired from Pubmed as well as the EPO and clinicaltrials.gov websites, which were subsequently analyzed and summarized according to targets, chemical structures and biological activities. Results: Neddylation as a sophisticated procedure comprises proteolytic processing of NEDD8 precursor, deploying conjugating enzymes E1 (NAE), E2 (UBE2M and UBE2F) and various E3, as well as translocating NEDD8 along these conjugating enzymes sequentially and finally to substrate proteins. Among these nodes, NAE, UBE2M and the interaction between UBE2M-DCN1 have been targeted by small molecules, metal complexes, peptides and RNAi. A NAE inhibitor pevonedistat (MLN4924) is currently under evaluation in clinical trials for the treatment of various cancers. Conclusion: With multiple inhibitory approaches of neddylation being introduced, the development of neddylation interference as a novel cancer therapy is significantly boosted recently, although its efficacy and the best way to achieve that are still to be demonstrated in clinical trials.