Entinostat augments NK cell functions via epigenetic upregulation of IFIT1-STING-STAT4 pathway

Abstract

Histone deacetylase inhibitors (HDACi) are an emerging cancer therapy; however, their effect on natural killer (NK) cell-mediated anti-tumor responses remain unknown. Here, we evaluated the impact of a benzamide HDACi, entinostat, on human primary NK cells as well as tumor cell lines. Entinostat significantly upregulated the expression of NKG2D, an essential NK cell activating receptor. Independently, entinostat augmented the expression of ULBP1, HLA, and MICA/B on both rhabdomyosarcoma and Ewing sarcoma cell lines. Additionally, entinostat increased both cytotoxicity and IFN-γ production in human NK cells following coculture with these tumor cells. Mechanistically, entinostat treatment resulted in increased chromatin accessibility to the promoter region for interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) gene and thereby increasing the transcript and protein levels of IFIT1 that augmented the IFIT1-mediated IRF1, STAT4, and STING pathways. Corresponding transcriptome analysis revealed enrichment of IRF1 and STAT4 and gene sets responsible for NK cell-mediated IFN-γ production and cytotoxicity, respectively. Our results show a novel mechanism by which entinostat initiates an IFIT1-STINGmediated potentiation of STAT4 via IRF1 to augment NK cell-mediated anti-tumor responses.

The Oncoprotein SKI Acts as A Suppressor of NK Cell-Mediated Immunosurveillance in PDAC

“…HDACi may also impact directly on NK cells, for example, via up-regulation of NKG2D and stimulation of IFNg release and toxicity in NK-tumor cell co-cultures [ 32 ]. However, HDACi monotherapy was already tested in clinical trials but received rather disappointing results [ 33 ].…”

Immunomodulatory Effects of Histone Deacetylation Inhibitors in Graft-vs.-Host Disease After Allogeneic Stem Cell Transplantation

“…Furthermore, the killing function of NK cells was also enhanced. In terms of its mechanism, entinostat increases the accessibility of the chromatin in the promoter region of interferon-induced protein with tetratripeptide repeats 1 (IFIT1), thus upregulating the mRNA and protein expression levels of IFIT1 and enhancing the IFIT1–STING–STAT4 pathways mediated by IFIT1 ( 52 ). However, further studies investigating whether HDACi also promotes the killing function of NK cells by regulating acetylation, thereby eliminating recipient APCs and inhibiting GVHD, are warranted.…”

Prospects for NK Cell Therapy of Sarcoma

“…Further, entinostat downregulates c-FLIP expression concomitantly redirecting Fas cellular localization to the lipid rafts, sensitizing sarcoma cells to FasL-mediated apoptosis [ 129 , 196 ]. Other groups have shown that entinostat increases the expression of MICA/B, ULBP1/2/5/6, and CD155 in OS, RMS, and EWS cells, enhancing NK cell cytotoxicity [ 197 , 198 ]. However, in a nude mice OS lung metastases model, no significant effects of the treatment were observed.…”

“…The lack of efficacy was linked with the failure of NK cells to penetrate inside the tumor nodules [ 197 ]. Besides, although preliminary studies report entinostat-mediated enhancement of NK cell effector function, both HDAC inhibition and DNA hypomethylation have been linked to NK cell cytotoxicity impairment, raising caution against combining them with NK cell-based therapies [ 198 , 199 , 200 ].…”