Romidepsin in peripheral and cutaneous T-cell lymphoma: mechanistic implications from clinical and correlative data

Oxidative stress-mediated epigenetic remodeling, metastatic progression and cell signaling in cancer

Cancer is a serious public health issue and cases are rising at a high rate around the world. Altered production of reactive oxygen species (ROS) causes oxidative stress (OS) which plays a vital role in cancer development by disrupting signaling pathways and genomic integrity in the cellular microenvironment. In this study, we reviewed the regulation of noncoding RNAs, histone modifications, and DNA methylation which OS is involved in. These mechanisms promote cancer growth, metastasis, and resistance to chemotherapeutic agents. There is significant potential to improve patient outcomes through the development of customized medications and interventions that precisely address the role of OS in the onset and progression of cancer. Redox-modulating drugs, antioxidant-based therapies, and measures to restore regular cellular activity and OS-modulated signaling pathways are some examples of these strategies. One other hypothesis rationalizes the cancer-suppressing effect of OS, which acts as a two-edged condition that warns against the use of antioxidants for cancer treatment and management. The present study was executed to review the impact of OS on epigenetic machinery, the evolution of metastatic cancer, and how OS mediates cellular signaling. Along with, insights into the potential of targeting OS-mediated mechanisms for cancer therapy.

Combined HDAC and eIF4A inhibition: A novel epigenetic therapy for pancreatic adenocarcinoma

Pancreatic ductal adenocarcinoma-(PDAC) needs innovative approaches due to its 12% 5-year survival despite current therapies. We show marked sensitivity of pancreatic cancer cells to the combination of a novel eIF4A inhibitor, des-methyl pateamine A (DMPatA), and a histone deacetylase inhibitor, romidepsin, inducing epigenetic reprogramming as an innovative therapeutic strategy. Exploring the mechanistic activity of this combination showed that with a short duration of romidepsin at low doses, robust acetylation persisted up to 48h with the combination, while histone acetylation rapidly faded with monotherapy. This represents an unexpected mechanism of action against PDAC cells that triggers transcriptional overload, metabolic stress, and augmented DNA damage. Structurally different class I HDAC inhibitors exhibit the same hyperacetylation patterns when co-administered with DMPatA, suggesting a class effect. We show efficacy of this combination regimen against tumor growth in a MIA PaCa-2 xenograft model of PDAC with persistent hyperacetylation confirmed in tumor samples.

STATEMENT OF SIGNIFICANCE

Pancreatic ductal adenocarcinoma, a significant clinical challenge, could benefit from the latent potential of epigenetic therapies like HDAC inhibitors-(HDIs), typically limited to hematological malignancies. Our study shows that a synergistic low dose combination of HDIs with an eIF4A-inhibitor in pancreatic cancer models results in marked pre-clinical efficacy, offering a promising new treatment strategy.

Romidepsin and Afatinib Abrogate Jak-Signal Transducer and Activator of Transcription Signaling and Elicit Synergistic Antitumor Effects in Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphomas are mature lymphoid neoplasias resulting from the malignant transformation of skin-resident T-cells. A distinctive clinical feature of cutaneous T-cell lymphomas is their sensitivity to treatment with histone deacetylase inhibitors. However, responses to histone deacetylase inhibitor therapy are universally transient and noncurative, highlighting the need for effective and durable drug combinations. In this study, we demonstrate that the combination of romidepsin, a selective class I histone deacetylase inhibitor, with afatinib, an EGFR family inhibitor, induces strongly synergistic antitumor effects in cutaneous T-cell lymphoma models in vitro and in vivo through abrogation of Jak-signal transducer and activator of transcription signaling. These results support a previously unrecognized potential role for histone deacetylase inhibitor plus afatinib combination in the treatment of cutaneous T-cell lymphomas.

The clinical regimens and cell membrane camouflaged nanodrug delivery systems in hematologic malignancies treatment

Hematologic malignancies (HMs), also referred to as hematological or blood cancers, pose significant threats to patients as they impact the blood, bone marrow, and lymphatic system. Despite significant clinical strategies using chemotherapy, radiotherapy, stem cell transplantation, targeted molecular therapy, or immunotherapy, the five-year overall survival of patients with HMs is still low. Fortunately, recent studies demonstrate that the nanodrug delivery system holds the potential to address these challenges and foster effective anti-HMs with precise treatment. In particular, cell membrane camouflaged nanodrug offers enhanced drug targeting, reduced toxicity and side effects, and/or improved immune response to HMs. This review firstly introduces the merits and demerits of clinical strategies in HMs treatment, and then summarizes the types, advantages, and disadvantages of current nanocarriers helping drug delivery in HMs treatment. Furthermore, the types, functions, and mechanisms of cell membrane fragments that help nanodrugs specifically targeted to and accumulate in HM lesions are introduced in detail. Finally, suggestions are given about their clinical translation and future designs on the surface of nanodrugs with multiple functions to improve therapeutic efficiency for cancers.

Clinical advances in epigenetic therapies for lymphoma

BACKGROUND

Advances in understanding of cancer biology, genomics, epigenomics, and immunology have resulted in development of several therapeutic options that expand cancer care beyond traditional chemotherapy or radiotherapy, including individualized treatment strategies, novel treatments based on monotherapies or combination therapy to reduce toxicities, and implementation of strategies for overcoming resistance to anticancer therapy.

RESULTS

This review covers the latest applications of epigenetic therapies for treatment of B cell, T cell, and Hodgkin lymphomas, highlighting key clinical trial results with monotherapies and combination therapies from the main classes of epigenetic therapies, including inhibitors of DNA methyltransferases, protein arginine methyltransferases, enhancer of zeste homolog 2, histone deacetylases, and the bromodomain and extraterminal domain.

CONCLUSION

Epigenetic therapies are emerging as an attractive add-on to traditional chemotherapy and immunotherapy regimens. New classes of epigenetic therapies promise low toxicity and may work synergistically with other cancer treatments to overcome drug resistance mechanisms.

New insights into epigenetic regulation of resistance to PD-1/PD-L1 blockade cancer immunotherapy: mechanisms and therapeutic opportunities

Programmed cell death protein 1(PD-1) is a type of immune-inhibitory checkpoint protein, which delivers inhibitory signals to cytotoxic T cells by binding to the programmed death ligand-1 (PD-L1) displayed on the surface of cancer cells. Antibodies blocking PD-1/PD-L1 interaction have been extensively used in treatment of human malignancies and have achieved promising outcomes in recent years. However, gradual development of resistance to PD-1/PD-L1 blockade has decreased the effectiveness of this immunotherapy in cancer patients. The underlying epigenetic mechanisms need to be elucidated for application of novel strategies overcoming this immunotherapy resistance. Epigenetic aberrations contribute to cancerogenesis by promoting different hallmarks of cancer. Moreover, these alterations may lead to therapy resistance, thereby leading to poor prognosis. Recently, the epigenetic regulatory drugs have been shown to decrease the resistance to PD-1/PD-L1 inhibitors in certain cancer patients. Inhibitors of the non-coding RNAs, DNA methyltransferases, and histone deacetylases combined with PD-1/PD-L1 inhibitors have shown considerable therapeutic efficacy against carcinomas as well as blood cancers. Importantly, DNA methylation-mediated epigenetic silencing can inhibit antigen processing and presentation, which promotes cancerogenesis and aggravates resistance to PD-1/PD-L1 blockade immunotherapy. These observations altogether suggest that the combination of the epigenetic regulatory drugs with PD-1/PD-L1 inhibitors may present potential solution to the resistance caused by monotherapy of PD-1/PD-L1 immunotherapy.

Utilizing an Endogenous Progesterone Receptor Reporter Gene for Drug Screening and Mechanistic Study in Endometrial Cancer

Expression of progesterone receptor (PR) is a favorable prognostic marker for multiple solid tumors. However, PR expression is reduced or lost in malignant tumors. Thus, monitoring and restoring functional PR expression is important in order to sensitize tumor cells to progesterone therapy in endometrial cancer. We developed stable PR reporter gene containing endometrial cancer cell lines monitoring the endogenous PR expression by inserting mCherry and hygromycin resistant gene at the endogenous PR gene locus by CRISPR/Cas9-mediated genome editing technique. This allows efficient, real-time monitoring of PR expression in its native epigenetic landscape. Reporter gene expression faithfully reflects and amplifies PR expression following treatment with drugs known to induce PR expression. Small molecular PR inducers have been identified from the FDA-approved 1018 drug library and tested for their ability to restore PR expression. Additionally, several candidate PR repressors have been identified by screening the genome-wide CRISPR knockout (GeCKO) library. This novel endogenous PR reporter gene system facilitates the discovery of a new treatment strategy to enhance PR expression and further sensitize progestin therapy in endometrial cancer. These tools provide a systematic, unbiased approach for monitoring target gene expression, allowing for novel drug discovery and mechanistic exploration.

R-Loop-Mediated ssDNA Breaks Accumulate Following Short-Term Exposure to the HDAC Inhibitor Romidepsin

Histone deacetylase inhibitors (HDACi) induce hyperacetylation of histones by blocking HDAC catalytic sites. Despite regulatory approvals in hematological malignancies, limited solid tumor clinical activity has constrained their potential, arguing for better understanding of mechanisms of action (MOA). Multiple activities of HDACis have been demonstrated, dependent on cell context, beyond the canonical induction of gene expression. Here, using a clinically relevant exposure duration, we established DNA damage as the dominant signature using the NCI-60 cell line database and then focused on the mechanism by which hyperacetylation induces DNA damage. We identified accumulation of DNA-RNA hybrids (R-loops) following romidepsin-induced histone hyperacetylation, with single-stranded DNA (ssDNA) breaks detected by single-cell electrophoresis. Our data suggest that transcription-coupled base excision repair (BER) is involved in resolving ssDNA breaks that, when overwhelmed, evolve to lethal dsDNA breaks. We show that inhibition of BER proteins such as PARP will increase dsDNA breaks in this context. These studies establish accumulation of R-loops as a consequence of romidepsin-mediated histone hyperacetylation. We believe that the insights provided will inform design of more effective combination therapy with HDACis for treatment of solid tumors. IMPLICATIONS: Key HDAC inhibitor mechanisms of action remain unknown; we identify accumulation of DNA-RNA hybrids (R-loops) due to chromatin hyperacetylation that provokes single-stranded DNA damage as a first step toward cell death.

New nonchemotherapy treatment options for cutaneous T-cell lymphomas

INTRODUCTION

The most common types of CTCL are mycosis fungoides (MF) and Sézary syndrome (SS). In both MF and SS, complete responses to treatment are uncommon. Recent developments and understanding of the biology of MF/SS have led to novel agents which may offer prolonged responses with less toxicity compared to conventional chemotherapy approaches.

AREAS COVERED

In this review, we discuss the efficacy and safety of new nonchemotherapy treatment options including antibody agents, small molecule inhibitors, fusion proteins, and CAR T-cell therapy. We also reflect on older immunomodulatory treatments including retinoids and histone deacetylase inhibitors.

EXPERT OPINION

Patients with MF/SS who require systemic therapy often progress through multiple agents sequentially, thus the need for additional novel agents in the treatment armamentarium. Antibody-based therapies such as alemtuzumab are highly effective in the blood compartment of disease, while brentuximab vedotin has shown higher activity in skin and lymph nodes. Checkpoint inhibitors may play a role in treating MF/SS but may induce hyperprogression, and engineered T cells and bispecific antibodies recruiting immune effectors are being developed and may show promise in the future.

Epigenetics in the Pathogenesis and Treatment of Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphomas (CTCLs) comprise a group of heterogeneous diseases involving malignant T cells. The pathogenesis and etiology of CTCL are still unclear, although a large number of genetic and epidemiological studies on CTCL have been conducted. Most CTCLs have an indolent course, making early diagnosis difficult. Once large-cell transformation occurs, CTCL progresses to more aggressive types, resulting in an overall survival of less than five years. Epigenetic drugs, which have shown certain curative effects, have been selected as third-line drugs in patients with relapsing and refractory CTCL. Many studies have also identified epigenetic biomarkers from tissues and peripheral blood of patients with CTCL and suggested that epigenetic changes play a role in malignant transformation and histone deacetylase inhibitor (HDACi) resistance in CTCL. Single-cell sequencing has been applied in CTCL studies, revealing heterogeneity in CTCL malignant T cells. The mechanisms of HDACi resistance have also been described, further facilitating the discovery of novel HDACi targets. Despite the heterogeneity of CTCL disease and its obscure pathogenesis, more epigenetic abnormalities have been gradually discovered recently, which not only enables us to understand CTCL disease further but also improves our understanding of the specific role of epigenetics in the pathogenesis and treatment. In this review, we discuss the recent discoveries concerning the pathological roles of epigenetics and epigenetic therapy in CTCL.

Jak-STAT Inhibition Mediates Romidepsin and Mechlorethamine Synergism in Cutaneous T-Cell Lymphoma

Sézary syndrome is an aggressive and disseminated form of cutaneous T-cell lymphoma associated with dismal prognosis in which the histone deacetylase inhibitor romidepsin has shown remarkable activity as a single agent. However, clinical responses to romidepsin are typically transient, highlighting the need for more effective therapies. In this study, we show synergistic antilymphoma effects of romidepsin in combination with mechlorethamine, an alkylating agent, in cutaneous T-cell lymphoma cell lines and primary samples with strong antitumor effects in an in vivo model of Sézary syndrome. Mechanistically, gene expression profiling points to abrogation of Jak/signal transducer and activator of transcription (STAT) signaling as an important mediator of this interaction. Consistently, the combination of mechlorethamine plus romidepsin resulted in downregulation of STAT5 phosphorylation in romidepsin-sensitive cell lines and primary Sézary syndrome samples, but not in romidepsin-resistant tumors. Moreover, in further support of Jak/STAT signaling as a modulator of romidepsin activity in cutaneous T-cell lymphoma, treatment with romidepsin in combination with Jak inhibitors resulted in markedly increased therapeutic responses. Overall, these results support a role for romidepsin plus mechlorethamine in combination in the treatment of cutaneous T-cell lymphoma and uncover a previously unrecognized role for Jak/STAT signaling in the response to romidepsin and romidepsin-based combination therapies in Sézary syndrome.

Novel therapeutic approaches for cutaneous T cell lymphomas

Introduction: Cutaneous T-cell lymphoma (CTCL) is a rare non-Hodgkin's lymphoma, characterized by malignant T cells infiltrating the skin. CTCL exhibits vast heterogeneity which complicates diagnosis and therapeutic strategies. Current CTCL treatment includes skin-directed therapies (such as topical corticosteroid, topical mechlorethamine, topical bexarotene, ultraviolet phototherapy and localized radiotherapy), total skin electron beam therapy and systemic therapies. Elucidation of molecular and signaling pathways underlying CTCL pathogenesis leads to identification of innovative and personalized treatment schemes.Areas covered: The authors reviewed the molecular and immunological aspects of CTCL with special focus on Mycosis Fungoides (MF), Sézary Syndrome (SS) and associated systemic treatment. A literature search was conducted in PubMed and Web of Science for peer-reviewed articles published until November 2020. Novel treatment approaches including retinoids, targeted therapies, immune checkpoint and JAK/STAT inhibitors, histones deacetylase (HDAC) and mTOR inhibitors as well as proteasome inhibitors, are discussed as potential therapeutic tools for the treatment of CTCL.Expert opinion: Novel therapeutic agents exhibit potential beneficial effects in CTCL patients of high need for therapy such as refractory early stage cutaneous and advanced stage disease. Therapeutic schemes employing a combination of novel agents with current treatment options may prove valuable for the future management of CTCL patients.

Epigenetics of cutaneous T-cell lymphoma: biomarkers and therapeutic potentials

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of skin-homing non-Hodgkin lymphomas. There are limited options for effective treatment of patients with advanced-stage CTCL, leading to a poor survival rate. Epigenetics plays a pivotal role in regulating gene expression without altering the DNA sequence. Epigenetic alterations are involved in virtually all key cancer-associated pathways and are fundamental to the genesis of cancer. In recent years, the epigenetic hallmarks of CTCL have been gradually elucidated and their potential values in the diagnosis, prognosis, and therapeutic intervention have been clarified. In this review, we summarize the current knowledge of the best-studied epigenetic modifications in CTCL, including DNA methylation, histone modifications, microRNAs, and chromatin remodelers. These epigenetic regulators are essential in the development of CTCL and provide new insights into the clinical treatments of this refractory disease.

Epigenetic alterations and advancement of treatment in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a rare and heterogeneous group of clinically aggressive diseases associated with poor prognosis. Except for ALK + anaplastic large-cell lymphoma (ALCL), most peripheral T-cell lymphomas are highly malignant and have an aggressive disease course and poor clinical outcomes, with a poor remission rate and frequent relapse after first-line treatment. Aberrant epigenetic alterations play an important role in the pathogenesis and development of specific types of peripheral T-cell lymphoma, including the regulation of the expression of genes and signal transduction. The most common epigenetic alterations are DNA methylation and histone modification. Histone modification alters the level of gene expression by regulating the acetylation status of lysine residues on the promoter surrounding histones, often leading to the silencing of tumour suppressor genes or the overexpression of proto-oncogenes in lymphoma. DNA methylation refers to CpG islands, generally leading to tumour suppressor gene transcriptional silencing. Genetic studies have also shown that some recurrent mutations in genes involved in the epigenetic machinery, including TET2, IDH2-R172, DNMT3A, RHOA, CD28, IDH2, TET2, MLL2, KMT2A, KDM6A, CREBBP, and EP300, have been observed in cases of PTCL. The aberrant expression of miRNAs has also gradually become a diagnostic biomarker. These provide a reasonable molecular mechanism for epigenetic modifying drugs in the treatment of PTCL. As epigenetic drugs implicated in lymphoma have been continually reported in recent years, many new ideas for the diagnosis, treatment, and prognosis of PTCL originate from epigenetics in recent years. Novel epigenetic-targeted drugs have shown good tolerance and therapeutic effects in the treatment of peripheral T-cell lymphoma as monotherapy or combination therapy. NCCN Clinical Practice Guidelines also recommended epigenetic drugs for PTCL subtypes as second-line therapy. Epigenetic mechanisms provide new directions and therapeutic strategies for the research and treatment of peripheral T-cell lymphoma. Therefore, this paper mainly reviews the epigenetic changes in the pathogenesis of peripheral T-cell lymphoma and the advancement of epigenetic-targeted drugs in the treatment of peripheral T-cell lymphoma (PTCL).

Xenograft and cell culture models of Sézary syndrome reveal cell of origin diversity and subclonal heterogeneity

Sézary Syndrome (SS) is a rare aggressive epidermotropic cutaneous T-cell lymphoma (CTCL) defined by erythroderma, pruritis, and a circulating atypical CD4 + T-cell clonal population. The diversity of Sézary cell (SC) phenotype and genotype may reflect either plasticity or heterogeneity, which was difficult to evaluate dynamically until the achievement of long-term SC expansion. Therefore, we developed six defined culture conditions allowing for the expansion of SC defined by their phenotype and monoclonality in four of seven SS cases. Engraftment of SC through the intrafemoral route into immunodeficient NOD.Cg-Prkdc(scid)Il2rg(tm1Wjll)/SzJ (NSG) mice was achieved in 2 of 14 SS cases. Secondary xenograft by percutaneous injection mimicked most of the features of SS with dermal infiltration, epidermotropism, and blood spreading. These models also allowed assessing the intra-individual heterogeneity of patient SC. Subclones sharing the same TCR gene rearrangement evolved independently according to culture conditions and/or after xenografting. This clonal selection was associated with some immunophenotypic plasticity and limited genomic evolution both in vitro and in vivo. The long-term amplification of SC allowed us to develop eight new SC lines derived from four different patients. These lines represent the cell of origin diversity of SC and provide new tools to evaluate their functional hallmarks and response to therapy.

Targeting epigenetic regulators in the treatment of T-cell lymphoma

Introduction: T-cell lymphomas represent a broad group of malignant T-cell neoplasms with marked molecular, clinical, and biologic heterogeneity. Survival rates after conventional chemotherapy regimens are poor for most subtypes and new therapies are needed. Rapidly expanding knowledge in the field of epigenomics and the development of an increasing number of epigenetic-modifying agents have created new opportunities for epigenetic therapies for patients with this complex group of diseases.Areas covered: The present review summarizes current knowledge on epigenetic alterations in T-cell lymphomas, availability, and mechanisms of action of epigenetic-modifying agents, results of clinical trials of epigenetic therapies in T-cell lymphomas, status of FDA approval, and biomarker approaches to guide therapy. Promising future directions are discussed.Expert opinion: Mutations in epigenetic-modifying genes are among the most common genetic alterations in T-cell lymphomas, highlighting the potential for epigenetic therapies to improve management of this group of diseases. Single-agent efficacy is well documented, leading to FDA approval for several indications, but overall response rates and durability of responses remain modest. Critical next steps for the field include optimizing combination therapies that incorporate epigenetic-modifying agents and developing predictive biomarkers that help guide patient and drug selection.

A high-throughput screening identifies histone deacetylase inhibitors as therapeutic agents against medulloblastoma

BACKGROUND

Medulloblastoma is the most frequently occurring malignant brain tumor in children. Current treatment strategies for medulloblastoma include aggressive surgery, cranio-spinal irradiation and adjuvant chemotherapy. Because current treatments can cause severe long-term side effects and are not curative, successful treatment remains a challenge.

METHODS

In this study, we employed a high-throughput cell viability assay to screen 12,800 compounds and to identify drug candidates with anti-proliferative properties for medulloblastoma cells. We also tested these compounds for attenuating medulloblastoma tumor development using mouse xenografts.

RESULTS

We identified two histone deacetylase inhibitors (dacinostat and quisinostat) with anti-proliferative properties for medulloblastoma cells. We showed that both compounds induce cytotoxicity, trigger cell apoptosis, and block cell cycle progression at the G2/M phase. In addition, dacinostat and quisinostat attenuated xenograft medulloblastoma growth in mice.

CONCLUSIONS

Our findings suggest that histone deacetylase inhibitors are potent therapeutic agents against medulloblastoma.

Quantitative Proteome Landscape of the NCI-60 Cancer Cell Lines

Here we describe a proteomic data resource for the NCI-60 cell lines generated by pressure cycling technology and SWATH mass spectrometry. We developed the DIA-expert software to curate and visualize the SWATH data, leading to reproducible detection of over 3,100 SwissProt proteotypic proteins and systematic quantification of pathway activities. Stoichiometric relationships of interacting proteins for DNA replication, repair, the chromatin remodeling NuRD complex, β-catenin, RNA metabolism, and prefoldins are more evident than that at the mRNA level. The data are available in CellMiner (discover.nci.nih.gov/cellminercdb and discover.nci.nih.gov/cellminer), allowing casual users to test hypotheses and perform integrative, cross-database analyses of multi-omic drug response correlations for over 20,000 drugs. We demonstrate the value of proteome data in predicting drug response for over 240 clinically relevant chemotherapeutic and targeted therapies. In summary, we present a novel proteome resource for the NCI-60, together with relevant software tools, and demonstrate the benefit of proteome analyses.

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High-quality NCI-60 proteotypes created using pressure cycling technology and SWATH-MS

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Proteotypes improve drug response prediction in multi-omics regression analysis

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∼3000 measured proteins allow investigation into protein complex stoichiometry

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CellMinerCDB (discover.nci.nih.gov/cellminercdb) portal allows dataset exploration

Current Status of HDAC Inhibitors in Cutaneous T-cell Lymphoma

Cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of lymphomas that are characterized by primary skin involvement. Mycosis fungoides (MF) and Sézary syndrome (SS), the two most common subtypes of CTCL, can be difficult to manage clinically as there are few effective treatment options available. Recently, histone deacetylase inhibitors (HDACi) have emerged as promising therapies with favorable adverse effect profiles, compared with traditional chemotherapies. In this article, we review the published literature to evaluate the role of HDACi in the treatment of CTCL. Specifically, we (1) briefly discuss the molecular rationale for the use of HDACi in CTCL; (2) compare the efficacy, tolerability, and adverse effects of HDACi; (3) review the cardiac safety data; and (4) discuss optimization of therapy with HDACi in the treatment of CTCL.

Drug-based perturbation screen uncovers synergistic drug combinations in Burkitt lymphoma

Burkitt lymphoma (BL) is a highly aggressive B-cell lymphoma associated with MYC translocation. Here, we describe drug response profiling of 42 blood cancer cell lines including 17 BL to 32 drugs targeting key cancer pathways and provide a systematic study of drug combinations in BL cell lines. Based on drug response, we identified cell line specific sensitivities, i.e. to venetoclax driven by BCL2 overexpression and partitioned subsets of BL driven by response to kinase inhibitors. In the combination screen, including BET, BTK and PI3K inhibitors, we identified synergistic combinations of PI3K and BTK inhibition with drugs targeting Akt, mTOR, BET and doxorubicin. A detailed comparison of PI3K and BTKi combinations identified subtle differences, in line with convergent pathway activity. Most synergistic combinations were identified for the BET inhibitor OTX015, which showed synergistic effects for 41% of combinations including inhibitors of PI3K/AKT/mTOR signalling. The strongest synergy was observed for the combination of the CDK 2/7/9 inhibitor SNS032 and OTX015. Our data provide a landscape of drug combination effects in BL and suggest that targeting CDK and BET could provide a novel vulnerability of BL.

The HDAC6/8/10 inhibitor TH34 induces DNA damage-mediated cell death in human high-grade neuroblastoma cell lines

High histone deacetylase (HDAC) 8 and HDAC10 expression levels have been identified as predictors of exceptionally poor outcomes in neuroblastoma, the most common extracranial solid tumor in childhood. HDAC8 inhibition synergizes with retinoic acid treatment to induce neuroblast maturation in vitro and to inhibit neuroblastoma xenograft growth in vivo. HDAC10 inhibition increases intracellular accumulation of chemotherapeutics through interference with lysosomal homeostasis, ultimately leading to cell death in cultured neuroblastoma cells. So far, no HDAC inhibitor covering HDAC8 and HDAC10 at micromolar concentrations without inhibiting HDACs 1, 2 and 3 has been described. Here, we introduce TH34 (3-(N-benzylamino)-4-methylbenzhydroxamic acid), a novel HDAC6/8/10 inhibitor for neuroblastoma therapy. TH34 is well-tolerated by non-transformed human skin fibroblasts at concentrations up to 25 µM and modestly impairs colony growth in medulloblastoma cell lines, but specifically induces caspase-dependent programmed cell death in a concentration-dependent manner in several human neuroblastoma cell lines. In addition to the induction of DNA double-strand breaks, HDAC6/8/10 inhibition also leads to mitotic aberrations and cell-cycle arrest. Neuroblastoma cells display elevated levels of neuronal differentiation markers, mirrored by formation of neurite-like outgrowths under maintained TH34 treatment. Eventually, after long-term treatment, all neuroblastoma cells undergo cell death. The combination of TH34 with plasma-achievable concentrations of retinoic acid, a drug applied in neuroblastoma therapy, synergistically inhibits colony growth (combination index (CI) < 0.1 for 10 µM of each). In summary, our study supports using selective HDAC inhibitors as targeted antineoplastic agents and underlines the therapeutic potential of selective HDAC6/8/10 inhibition in high-grade neuroblastoma.

Systemic Treatment Options for Advanced-Stage Mycosis Fungoides and Sézary Syndrome

PURPOSE OF REVIEW

Cutaneous T-cell lymphoma (CTCL) is a rare form of non-Hodgkin lymphoma. Globally, the most common subtypes of CTCL are mycosis fungoides and Sézary syndrome. CTCL can confer significant morbidity and even mortality in advanced disease. Here we review the current and potential future treatments for advanced-stage CTCL.

RECENT FINDINGS

Heterogeneity of treatment choice has been demonstrated both in US and non-US centers. Systemic treatment choice is currently guided by prognostic features, incorporating stage, immunophenotypic and molecular findings, and patient-specific factors such as age and comorbidities. Randomized controlled studies are uncommon, and the literature is composed predominantly of retrospective, cohort, and early-phase studies. International consensus guidelines are available; however, the lack of comparative trials means that there is no clear algorithmic approach to treatment. This review article reports on the systemic treatment options in current use for advanced CTCL, and on the possible future therapies, acknowledging that an algorithmic approach is not yet forthcoming to guide treatment prioritization.

Overcoming Resistance to DNA-Targeted Agents by Epigenetic Activation of Schlafen 11 (SLFN11) Expression with Class I Histone Deacetylase Inhibitors

Purpose: Schlafen 11 (SLFN11), a putative DNA/RNA helicase is a dominant genomic determinant of response to DNA-damaging agents and is frequently not expressed in cancer cells. Whether histone deacetylase (HDAC) inhibitors can be used to release SLFN11 and sensitize SLFN11-inactivated cancers to DNA-targeted agents is tested here.Experimental Design:SLFN11 expression was examined in The Cancer Genome Atlas (TCGA), in cancer cell line databases and in patients treated with romidepsin. Isogenic cells overexpressing or genetically inactivated for SLFN11 were used to investigate the effect of HDAC inhibitors on SLFN11 expression and sensitivity to DNA-damaging agents.Results:SLFN11 expression is suppressed in a broad fraction of common cancers and cancer cell lines. In cancer cells not expressing SLFN11, transfection of SLFN11 sensitized the cells to camptothecin, topotecan, hydroxyurea, and cisplatin but not to paclitaxel. SLFN11 mRNA and protein levels were strongly induced by class I (romidepsin, entinostat), but not class II (roclinostat) HDAC inhibitors in a broad panel of cancer cells. SLFN11 expression was also enhanced in peripheral blood mononuclear cells of patients with circulating cutaneous T-cell lymphoma treated with romidepsin. Consistent with the epigenetic regulation of SLFN11, camptothecin and class I HDAC inhibitors were synergistic in many of the cell lines tested.Conclusions: This study reports the prevalent epigenetic regulation of SLFN11 and the dominant stimulatory effect of HDAC inhibitors on SLFN11 expression. Our results provide a rationale for combining class I HDAC inhibitors and DNA-damaging agents to overcome epigenetic inactivation of SLFN11-mediated resistance to DNA-targeted agents. Clin Cancer Res; 24(8); 1944-53. ©2018 AACR.

Synergy of BCL2 and histone deacetylase inhibition against leukemic cells from cutaneous T-cell lymphoma patients

The presence and degree of peripheral blood involvement in patients with cutaneous T-cell lymphoma (CTCL) portend a worse clinical outcome. Available systemic therapies for CTCL may variably decrease tumor burden and improve quality of life, but offer limited effects on survival; thus, novel approaches to the treatment of advanced stages of this non-Hodgkin lymphoma are clearly warranted. Mutational analyses of CTCL patient peripheral blood malignant cell samples suggested the antiapoptotic mediator B-cell lymphoma 2 (BCL2) as a potential therapeutic target. To test this, we developed a screening assay for evaluating the sensitivity of CTCL cells to targeted molecular agents, and compared a novel BCL2 inhibitor, venetoclax, alone and in combination with a histone deacetylase (HDAC) inhibitor, vorinostat or romidepsin. Peripheral blood CTCL malignant cells were isolated from 25 patients and exposed ex vivo to the 3 drugs alone and in combination, and comparisons were made to 4 CTCL cell lines (Hut78, Sez4, HH, MyLa). The majority of CTCL patient samples were sensitive to venetoclax, and BCL2 expression levels were negatively correlated (r = -0.52; P =018) to 50% inhibitory concentration values. Furthermore, this anti-BCL2 effect was markedly potentiated by concurrent HDAC inhibition with 93% of samples treated with venetoclax and vorinostat and 73% of samples treated with venetoclax and romidepsin showing synergistic effects. These data strongly suggest that concurrent BCL2 and HDAC inhibition may offer synergy in the treatment of patients with advanced CTCL. By using combination therapies and correlating response to gene expression in this way, we hope to achieve more effective and personalized treatments for CTCL.

Responses to romidepsin in patients with cutaneous T-cell lymphoma and prior treatment with systemic chemotherapy

Cutaneous T-cell lymphomas (CTCL) are a group of non-Hodgkin lymphomas that typically present in the skin but can progress to systemic involvement. The optimal treatment for patients who relapse from or are refractory to systemic chemotherapy remains unclear. Romidepsin is a potent, class-I selective histone deacetylase inhibitor approved for the treatment of patients with CTCL who have had ≥1 prior systemic therapy. Here, we present a subanalysis of two phase-2 trials (NCT00106431, NCT00007345) of romidepsin in patients with CTCL who had prior treatment with systemic chemotherapy. Patients with prior chemotherapy were able to achieve durable responses to romidepsin, and response rates were similar to those in patients who were chemotherapy naïve. Overall, no new safety signals emerged in patients who had received prior chemotherapy. The data presented here suggest that romidepsin is safe and effective in patients with CTCL who received prior systemic chemotherapy.

The discovery and development of romidepsin for the treatment of T-cell lymphoma

INTRODUCTION

Romidepsin is a potent and selective inhibitor of histone deacetylases (HDCAi). It is also the only bicyclic inhibitor to undergo clinical assessment and is considered a promising drug for the treatment of T-cell lymphomas. The cellular action of romidepsin results in enhanced histone acetylation, as well as the acetylation of other nuclear or cytoplasmic proteins, influencing cell cycle, apoptosis, and angiogenesis. In phase II studies involving patients with relapsed or refractory of cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma (PTCL), romidepsin produced overall response rates (ORR) of 34-35% and 25-38%, with complete response (CR) rates of 6% and 15-18%, respectively. Areas covered: This review summarizes the development of romidepsin, the mechanisms behind its antineoplastic action and its pharmacology. It also covers its pharmacokinetic and pharmacodynamic properties, as well as the preclinical and clinical data on its activity in T-cell lymphoma. Expert opinion: Since there are only few effective therapies available for T-cell lymphomas, romidepsin is a valuable option for relapsed/refractory patients with both CTCL and PTCL. It's also generally well tolerated, and gives potentially durable responses for patients with advanced and symptomatic disease. Combinations of romidepsin with other antineoplastic agents may also further improve drug response and outcomes in T-cell lymphoma.

Romidepsin is effective and well tolerated in older patients with peripheral T-cell lymphoma: analysis of two phase II trials

Peripheral T-cell lymphomas (PTCLs) are a rare group of lymphoid neoplasms with high relapse rates after initial therapy and poor prognosis. Most patients are aged ≥60 years and are often not candidates for aggressive salvage therapies. Romidepsin, a potent class I histone deacetylase inhibitor, has shown significant single-agent activity in relapsed/refractory PTCL. We evaluated the efficacy and tolerability of romidepsin in elderly patients in this setting. Ninety-five patients aged ≥60 years were identified from 2 prospective phase 2 registration trials of romidepsin, and comparative analyses were performed with younger patients from these trials. Response rates, progression-free survival, and overall survival were not statistically different for younger vs older patients. The toxicity profile in older and younger patients was similar in both trials. Romidepsin demonstrated similar efficacy and tolerability in younger and older patients and presents an attractive treatment option for relapsed/refractory PTCL regardless of age.

TRIAL REGISTRATION

Clinicaltrials.gov identifiers: NCT00426764, NCT00007345.

Responses to romidepsin by line of therapy in patients with relapsed or refractory peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of aggressive non-Hodgkin lymphomas typically associated with poor prognosis. Most patients with PTCL receive chemotherapy as first-line treatment, but many experience rapid relapse. For patients with relapsed/refractory PTCL, responses to treatment and long-term outcomes tend to worsen with increasing lines of therapy. Romidepsin is a potent class I histone deacetylase inhibitor approved by the US Food and Drug Administration for the treatment of PTCL in patients who have received ≥1 prior therapy. A pivotal phase 2 trial of romidepsin in patients with relapsed/refractory PTCL demonstrated an objective response rate of 25% (33/130), including 15% with confirmed/unconfirmed complete response, and a median duration of response of 28 months. In the analysis presented herein, romidepsin was shown to have similar responses and long-term outcomes in patients with 1, 2, and ≥3 prior lines of treatment, including in patients with disease refractory to the last prior therapy. Although adverse events increased with increasing lines of treatment, the rate of dose modifications and discontinuations due to adverse events was not significantly different. These data support the use of romidepsin as salvage treatment for PTCL irrespective of the number of prior therapies.

Targeting histone deacetylases in T-cell lymphoma

Histone deacetylase inhibitors (HDACi) are epigenetic modifiers with single-agent activity in patients with cutaneous and peripheral T-cell lymphoma (CTCL, PTCL). The mechanisms for this preferential activity remain unclear, and although some would term this as 'class effect,' there are differences in efficacy and safety, likely a result of the varying chemical structures/classes, histone and non-histone targets, potencies, and clinical dosing for each. Three HDACi have single-agent approval in relapsed/refractory TCL in the United States: romidepsin in CTCL and PTCL, vorinostat in CTCL, and belinostat in PTCL. Although comparison of these agents is difficult due to differences in patient populations, through this review we aimed to provide a detailed overview of the clinical data for HDACi in TCL and their use in clinical practice. Despite early concerns, data demonstrate the cardiac safety of HDACi, while highlighting the need to maintain electrolytes in the normal range and monitor QT interval when initially co-administering antiemetics or other drugs that prolong QT. To further improve response rates and durability of responses, HDACi are under clinical investigation in combination with chemotherapy regimens and various novel agents.

Pruritus Reduction with Systemic Anti-lymphoma Treatments in Patients with Cutaneous T Cell Lymphoma: A Narrative Review

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous and relatively rare group of non-Hodgkin lymphomas arising from neoplastic skin-homing memory T cells. There is no known cure for CTCL, and current treatments focus on achieving and maintaining remission, controlling symptoms, limiting toxicities and maintaining or improving quality of life. Patients with CTCL often suffer from pruritus (itching), which can be debilitating and can have a significant impact on physical well-being and quality of life. Although progress has been made towards understanding the mechanisms of pruritus, the pathophysiology of CTCL-related pruritus remains unclear. Currently, there is neither a step-wise treatment algorithm for CTCL nor a standardized approach to treating pruritus in patients with CTCL. Treatments which specifically target pruritus have been reported with varying effectiveness. However, systemic treatments that target CTCL have the potential to alleviate pruritus by treating the underlying disease. Several systemic CTCL treatments have reported anti-pruritic properties, some in both objective responders and nonresponders, but the lack of a standardized method to measure and report pruritus makes it difficult to compare the effectiveness of systemic treatments. In this review, we provide an overview of approved and investigational systemic CTCL treatments that report anti-pruritic properties. For each study, the methods used to measure and report pruritus, as well as the study design are examined so that the clinical benefits of each systemic treatment can be more readily evaluated.

Funding: Financial support for medical editorial assistance and article processing charge were provided by Celgene Corporation.

Romidepsin for the treatment of relapsed/refractory cutaneous T-cell lymphoma (mycosis fungoides/Sézary syndrome): Use in a community setting

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous group of rare non-Hodgkin lymphomas that arise in the skin. In advanced stages, CTCL becomes systemic and is associated with poor prognosis. Diagnosis of CTCL and treatment of early-stage disease with topical therapies often occurs under the care of a dermatologist. Community oncologists see few patients with CTCL due to direct referrals from dermatologists to academic or lymphoma specialty centers. However, some patients will continue to be managed in a community setting. Currently there is no evidence-based stepwise algorithm for treatment of patients with CTCL, and guidelines suggest a wide range of systemic therapies, including biologics, targeted agents, and more traditional chemotherapies. To provide optimal care in a community setting, oncologists must become familiar with newer nonchemotherapeutic treatment options. This review highlights romidepsin, a histone deacetylase inhibitor approved for the treatment of patients with CTCL who have received ≥1 prior systemic therapy.

How I treat mycosis fungoides and Sézary syndrome

Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma variant and is closely related to a rare leukemic variant, Sézary syndrome (SS). MF patients at risk of disease progression can now be identified and an international consortium has been established to address the prognostic relevance of specific biologic factors and define a prognostic index. There are a lack of randomized clinical trial data in MF/SS and evidence is based on a traditional “stage-based” approach; treatment of early-stage disease (IA-IIA) involves skin directed therapies which include topical corticosteroids, phototherapy (psoralen with UVA or UVB), topical chemotherapy, topical bexarotene, and radiotherapy including total skin electron beam therapy. Systemic approaches are used for refractory early-stage and advanced-stage disease (IIB-IV) and include bexarotene, interferon α, extracorporeal photopheresis, histone deacetylase inhibitors, and antibody therapies such as alemtuzumab, systemic chemotherapy, and allogeneic transplantation. However, despite the number of biologic agents available, the treatment of advanced-stage disease still represents an unmet medical need with short duration of responses. Encouragingly, randomized phase 3 trials are assessing novel agents, including brentuximab vedotin and the anti-CCR4 antibody, mogamulizumab. A broader understanding of the biology of MF/SS will hopefully identify more effective targeted therapies.

Romidepsin enhances the cytotoxicity of fludarabine, clofarabine and busulfan combination in malignant T-cells

Novel approaches to pre-transplant conditioning are needed to improve treatment of advanced T-cell malignancies. We investigated the synergism of fludarabine (Flu), clofarabine (Clo), busulfan (Bu), and romidepsin (Rom) in T-cell lines and patient-derived cell samples. [Flu+Clo+Bu+Rom] had combination indexes of 0.4-0.5 at ∼50% cytotoxicity in PEER and SUPT1 cells, suggesting synergism. Drug exposure resulted in histone modifications, DNA-damage response (DDR), increased reactive oxygen species (ROS), decreased glutathione (GSH) and mitochondrial membrane (MM) potential, and apoptosis. Similar activation of DDR and apoptosis was observed in patient samples. The PI3K-AKT-mTOR, NFκB, Raf-MEK-ERK, JAK-STAT and Wnt/β-catenin pro-survival pathways were inhibited by the 4-drug combination. The SAPK/JNK stress pathway was activated. A novel finding was the down-regulation of the drug transporter MRP1. We propose the following mechanisms of synergism: Flu, Clo and Rom induce histone modifications and chromatin remodeling, exposing DNA to Bu alkylation; the increased production of ROS, due to drug-mediated stress response and decreased GSH, damages the MM causing leakage of pro-apoptotic factors; down-regulation of MRP1 increases intracellular Bu concentration and exacerbates the DDR; and inhibition of multiple survival pathways. Our results provide the basis for a clinical trial to evaluate [Flu+Clo+Bu+Rom] as part of conditioning regimen for refractory T-cell malignancy patients undergoing stem cell transplantation.

Romidepsin targets multiple survival signaling pathways in malignant T cells

Romidepsin is a cyclic molecule that inhibits histone deacetylases. It is Food and Drug Administration-approved for treatment of cutaneous and peripheral T-cell lymphoma, but its precise mechanism of action against malignant T cells is unknown. To better understand the biological effects of romidepsin in these cells, we exposed PEER and SUPT1 T-cell lines, and a primary sample from T-cell lymphoma patient (Patient J) to romidepsin. We then examined the consequences in some key oncogenic signaling pathways. Romidepsin displayed IC₅₀ values of 10.8, 7.9 and 7.0 nm in PEER, SUPT1 and Patient J cells, respectively. Strong inhibition of histone deacetylases and demethylases, increased production of reactive oxygen species and decreased mitochondrial membrane potential were observed, which may contribute to the observed DNA-damage response and apoptosis. The stress-activated protein kinase/c-Jun N-terminal kinase signaling pathway and unfolded protein response in the endoplasmic reticulum were activated, whereas the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) and β-catenin pro-survival pathways were inhibited. The decreased level of β-catenin correlated with the upregulation of its inhibitor SFRP1 through romidepsin-mediated hypomethylation of its gene promoter. Our results provide new insights into how romidepsin invokes malignant T-cell killing, show evidence of its associated DNA hypomethylating activity and offer a rationale for the development of romidepsin-containing combination therapies.

Stabilizing versus destabilizing the microtubules: a double-edge sword for an effective cancer treatment option?

Microtubules are dynamic and structural cellular components involved in several cell functions, including cell shape, motility, and intracellular trafficking. In proliferating cells, they are essential components in the division process through the formation of the mitotic spindle. As a result of these functions, tubulin and microtubules are targets for anticancer agents. Microtubule-targeting agents can be divided into two groups: microtubule-stabilizing, and microtubule-destabilizing agents. The former bind to the tubulin polymer and stabilize microtubules, while the latter bind to the tubulin dimers and destabilize microtubules. Alteration of tubulin-microtubule equilibrium determines the disruption of the mitotic spindle, halting the cell cycle at the metaphase-anaphase transition and, eventually, resulting in cell death. Clinical application of earlier microtubule inhibitors, however, unfortunately showed several limits, such as neurological and bone marrow toxicity and the emergence of drug-resistant tumor cells. Here we review several natural and synthetic microtubule-targeting agents, which showed antitumor activity and increased efficacy in comparison to traditional drugs in various preclinical and clinical studies. Cryptophycins, combretastatins, ombrabulin, soblidotin, D-24851, epothilones and discodermolide were used in clinical trials. Some of them showed antiangiogenic and antivascular activity and others showed the ability to overcome multidrug resistance, supporting their possible use in chemotherapy.