Lactam-Based HDAC Inhibitors for Anticancer Chemotherapy: Restoration of RUNX3 by Posttranslational Modification and Epigenetic Control

Unusual Regio- and Chemoselectivity in Oxidation of Pyrroles and Indoles Enabled by a Thianthrenium Salt Intermediate

A dearomative oxidation of pyrroles to Δ3-pyrrol-2-ones is described, which employs a sulfoxide as oxidant, in conjunction with a carboxylic acid anhydride and a Brønsted acid additive. 3-substituted pyrroles undergo regioselective oxidation to give the product isomer in which oxygen has been introduced at the more hindered position. Regioselectivity is rationalized by a proposed mechanism that proceeds by initial thianthrenium introduction at the less-hindered pyrrole α-position, followed by distal attack of an oxygen nucleophile and subsequent elimination of thianthrene. The same reaction conditions are also able to effect a chemoselective oxidation of indoles to indolin-3-ones and additionally of indolin-3-ones to 2-hydroxyindolin-3-ones. Here again, the regio- and chemoselectivities are rationalized through the intermediacy of a thianthrenium salt.

Metabolism, HDACs, and HDAC Inhibitors: A Systems Biology Perspective

Histone deacetylases (HDACs) are epigenetic enzymes that play a central role in gene regulation and are sensitive to the metabolic state of the cell. The cross talk between metabolism and histone acetylation impacts numerous biological processes including development and immune function. HDAC inhibitors are being explored for treating cancers, viral infections, inflammation, neurodegenerative diseases, and metabolic disorders. However, how HDAC inhibitors impact cellular metabolism and how metabolism influences their potency is unclear. Discussed herein are recent applications and future potential of systems biology methods such as high throughput drug screens, cancer cell line profiling, single cell sequencing, proteomics, metabolomics, and computational modeling to uncover the interplay between metabolism, HDACs, and HDAC inhibitors. The synthesis of new systems technologies can ultimately help identify epigenomic and metabolic biomarkers for patient stratification and the design of effective therapeutics.

Improving potency and metabolic stability by introducing an alkenyl linker to pyridine-based histone deacetylase inhibitors for orally available RUNX3 modulators

RUNX3, a tumor suppressor, is suppressed in various cancers by abnormal epigenetic changes. Histone deacetylases (HDACs) can deacetylate the lysine residues of RUNX3, followed by degradation via a ubiquitin-mediated pathway. Inhibition of HDAC leads to functional restoration of the RUNX3 protein by epigenetic expression and RUNX3 protein stabilization. We previously reported a series of HDAC inhibitors that restored RUNX3 function. In the present study, we introduced an alkenyl linker group to pyridine-based HDAC inhibitors to improve their potencies and chemical properties. This alkenyl linker made the compounds more rigid, facilitating a better fit than alkyl moieties to the active site of HDAC proteins. Most compounds in this series exhibited potent RUNX activities, HDAC inhibitory activities, and inhibitory activities towards the growth of human cancer cell lines. Notably, one of these derivatives, (E)-3-(1-cinnamyl-2-oxo-1,2-dihydropyridin-3-yl)-N-hydroxyacrylamide (7k), showed excellent properties in a microsomal stability study, in a xenograft study, and in an in vivo pharmacokinetic evaluation. Modulation of RUNX3 therefore results in highly potent and orally available anticancer chemotherapeutic agents.

Retrospective Study of Adjuvant Chemotherapy Effects on Survival Rate after Three-Field Lymph Node Dissection for Stage IIA Esophageal Cancer

To determine the efficacy of postoperative adjuvant chemotherapy with paclitaxel plus cisplatin (Taxol+DDP, TP therapy) for stage IIA esophageal squamous cell carcinoma (ESCC) and to investigate the expression of RUNX3 in lymph node metastasis-negative esophageal cancer and its relationship with medical prognosis, a retrospective summary of clinical treatment of 143 cases of stage IIA esophageal squamous cell carcinoma patients was made. The patients were divided into two groups, a surgery alone control group (52 patients) and a chemotherapy group that received postoperative TP therapy (91 patients). The disease-free and 5 year survival rates were compared between the groups and a multivariate analysis of prognostic factors was performed. The same analysis was performed for cases classified as RUNX3 positive and negative, with post-operative specimens assessed by immunohistochemistry. Although the disease-free and 5 year survival rates in control and chemotherapy groups did not significantly differ and there was no significance in RUNX3 negative cases, postoperative adjuvant chemotherapy in the chemotherapy group was shown to improve disease-free and 5 year survival rate compared to the control group in RUNX3 positive cases. On Cox regression multivariate analysis, postoperative adjuvant chemotherapy (P<0.01) was an independent prognostic factor for RUNX3 positive cases, suggesting that postoperative TP may be effective as adjuvant chemotherapy for stage IIA esophageal cancer patients with RUNX3 positive lesions.

Discovery of Orally Available Runt-Related Transcription Factor 3 (RUNX3) Modulators for Anticancer Chemotherapy by Epigenetic Activation and Protein Stabilization

Recently, we identified a novel strategy for anticancer chemotherapy by restoring runt-related transcription factor 3 (RUNX3) levels via lactam-based histone deacetylase (HDAC) inhibitors that stabilize RUNX3. Described here are the synthesis, biological evaluation, and pharmacokinetic evaluation of new synthetic small molecules based on pyridone-based HDAC inhibitors that specifically stabilize RUNX3 by acetylation and regulate its function. Many of the newly synthesized compounds showed favorable RUNX activities, HDAC inhibitory activities, and inhibitory activities on the growth of human cancer cell lines. Notably, one of these new derivatives, (E)-N-hydroxy-3-(2-oxo-1-(quinolin-2-ylmethyl)-1,2-dihydropyridin-3-yl)acrylamide (4l), significantly restored RUNX3 in a dose-dependent manner and showed high metabolic stability, a good pharmacokinetic profile with high oral bioavailability and long half-life, and strong antitumor activity. This study suggests that pyridone-based analogues modulate RUNX3 activity through epigenetic regulation as well as strong transcriptional and post-translational regulation of RUNX3 and could be potential clinical candidates as orally available RUNX3 modulators for the treatment of cancer.