Low-dose HDACi potentiates anti-tumor activity of macrophages in immunotherapy

Intra-articular Histone Deacetylase Inhibitor Microcarrier Delivery to Reduce Osteoarthritis

The histone deacetylase inhibitor (HDACi) was a milestone in the treatment of refractory T-cell lymphoma. However, the beneficial effects of HDACi have not been appreciated in osteoarthritis (OA). Herein, we implemented a microcarrier system because of the outstanding advantages of controlled and sustained release, biodegradability, and biocompatibility. The poly(d,l-lactide-co-glycolide) (PLGA) microcapsules have a regulated and sustained release profile with a reduced initial burst release, which can improve the encapsulation efficiency of the Chidamide. The emulsion solvent evaporation strategy was used to encapsulate Chidamide in PLGA microcapsules. The encapsulation of Chidamide was established by UV-vis spectra and scanning electron microscopy. Additionally, the inhibition of Tnnt3 and immune stimulation by Chidamide helped to inhibit cartilage destruction and prevent articular cartilage degeneration. Based on the results, the Chidamide in PLGA microcapsules provides a transformative therapeutic strategy for the treatment of osteoarthritis patients to relieve symptoms and protect against cartilage degeneration.

A Cell-Based Screen Identifies HDAC Inhibitors as Activators of RIG-I Signaling

Enhancing the immune microenvironment in cancer by targeting the nucleic acid sensors is becoming a potent therapeutic strategy. Among the nucleic acid sensors, activation of the RNA sensor Retinoic Acid-inducible Gene (RIG-I) using small hairpin RNAs has been shown to elicit powerful innate and adaptive immune responses. Given the challenges inherent in pharmacokinetics and delivery of RNA based agonists, we set out to discover small molecule agonists of RIG-I using a cell-based assay. To this end, we established and validated a robust high throughput screening assay based on a commercially available HEK293 reporter cell line with a luciferase reporter downstream of tandem interferon stimulated gene 54 (ISG54) promoter elements. We first confirmed that the luminescence in this cell line is dependent on RIG-I and the interferon receptor using a hairpin RNA RIG-I agonist. We established a 96-well and a 384-well format HTS based on this cell line and performed a proof-of-concept screen using an FDA approved drug library of 1,200 compounds. Surprisingly, we found two HDAC inhibitors Entinostat, Mocetinostat and the PLK1 inhibitor Volasertib significantly enhanced ISG-luciferase activity. This luminescence was substantially diminished in the null reporter cell line indicating the increase in signaling was dependent on RIG-I expression. Combination treatment of tumor cell lines with Entinostat increased RIG-I induced cell death in a mammary carcinoma cell line that is resistant to either Entinostat or RIG-I agonist alone. Taken together, our data indicates an unexpected role for HDAC1,-3 inhibitors in enhancing RIG-I signaling and highlight potential opportunities for therapeutic combinations.