Preclinical Studies Support Combined Inhibition of BET Family Proteins and Histone Deacetylases as Epigenetic Therapy for Cutaneous T-Cell Lymphoma

Abstract

Advanced-stage cutaneous T-cell lymphoma (CTCL) is usually a fatal malignancy despite optimal use of currently available treatments. In this preclinical study of novel CTCL therapy, we performed in vitro and ex vivo experiments to determine the efficacy of combination treatment with a panel of BET bromodomain inhibitors (BETi) (JQ1, OTX015, CPI-0610, I-BET762) and HDAC inhibitors (HDACi) (SAHA/Vorinostat, Romidepsin). BETi/HDACi combinations were synergistic (combination index <1) against cell viability and induced G0/G1 cell cycle arrest. Apoptosis was uniformly enhanced. From a mechanistic standpoint, proliferative drivers c-Myc, Cyclin D1, NFkB, and IL-15Rα were reduced. Inhibitory CDKN1A was increased. CDKN1B, IL-7R, IL-17Rα, STAT3, and STAT5 alterations varied. There were significant increases in extrinsic apoptotic pathway death receptors and ligands (FasL, DR4, DR5, TRAIL, and TNFR1). At clinically tolerable levels of single agents, Romidepsin (1 nM) + OTX015 (125 nM) induced the greatest apoptosis (60%_80%) at 96 hours. Ex vivo studies of leukemic CTCL cells obtained from patients with Sezary syndrome also showed higher levels of apoptosis (about 60%-90%) in response to combination treatments relative to single agents. In contrast, combination treatment of normal CD4+ T cells induced only minimal apoptosis (<10%). Our findings show that the mechanism of action of BETi/HDACi therapy in CTCL involves induction of both cell cycle arrest and apoptosis with reduced proliferative drivers and enhanced expression of apoptotic extrinsic pathway death receptors and ligands. Relative to single agents, the superior anti-CTCL effects of BETi/HDACi combinations in vitro and ex vivo provide a rationale for clinical trials exploring their efficacy as therapy for CTCL.

Epigenetic regulation of defense genes by histone deacetylase1 in human cell line-derived macrophages promotes intracellular survival of Leishmania donovani

“…Vorinostat, also termed as suberoylanilidehydroxamic acid (SAHA) is a known class I and class II HDAC inhibitor [33]. It is FDA approved [34] for the treatment of cutaneous T cell lymphoma (CTCL) and Sezary syndrome [35,36]. It is also being evaluated for the treatment of various other oncology and HIV infection [37].…”

Epigenetic treatment combinations to effectively target cisplatin‐resistant germ cell tumors: past, present, and future considerations

“…They are the only domains, which bind specifically to histone acetylation marks (Jain & Barton, 2017). Even though combined treatment with HDAC and BET inhibitors (BETi) revealed additive or synergistic effects in several cancer entities, such as cutaneous T-cell lymphoma, neuroblastoma, glioblastoma, non-small cell lung cancer, adenocarcinoma, and colon cancer (Mazur et al, 2015;Shahbazi et al, 2016;Adeegbe et al, 2017;Meng et al, 2018;Rajendran et al, 2019;Zhao et al, 2019), so far only few studies described the mono-and combined treatment options with BETis in GCTs. Even though combined treatment with HDAC and BET inhibitors (BETi) revealed additive or synergistic effects in several cancer entities, such as cutaneous T-cell lymphoma, neuroblastoma, glioblastoma, non-small cell lung cancer, adenocarcinoma, and colon cancer (Mazur et al, 2015;Shahbazi et al, 2016;Adeegbe et al, 2017;Meng et al, 2018;Rajendran et al, 2019;Zhao et al, 2019), so far only few studies described the mono-and combined treatment options with BETis in GCTs.…”

“…Recently, the anti-cancer efficacy of inhibitors against the bromodomain and extra-terminal domain-containing (BET) protein family have been evaluated in several cancers, such as prostate, breast, colon, intestine, pancreas, liver, lung, brain, oral squamous cell carcinoma, and leukemias (Sahai et al, 2016;Saenz et al, 2017;Xu & Vakoc, 2017;Sahni & Keri, 2018;Zhang et al, 2018;Baldan et al, 2019). Even though combined treatment with HDAC and BET inhibitors (BETi) revealed additive or synergistic effects in several cancer entities, such as cutaneous T-cell lymphoma, neuroblastoma, glioblastoma, non-small cell lung cancer, adenocarcinoma, and colon cancer (Mazur et al, 2015;Shahbazi et al, 2016;Adeegbe et al, 2017;Meng et al, 2018;Rajendran et al, 2019;Zhao et al, 2019), so far only few studies described the mono-and combined treatment options with BETis in GCTs. The amount of transcripts of bromodomain-containing genes increases the higher the GCT stage is (Gashaw et al, 2005), indicating bromodomains being an interesting target for GCT treatment.…”

Update on Biology of Cutaneous T-Cell Lymphoma

“…The synergistic epigenetic-modulatory effect of histone acetylation of DNA demethylation results in global CpG methylation alterations as well as reexpression of tumor suppressor genes that was not achieved by single agent treatments (85). Preclinical and clinical investigations have demonstrated the combinatorial use of different epigenetic modulators together or in combination with other treatments (85)(86)(87)(88)(89)(90).…”