Impaired proteasome function activates GATA3 in T cells and upregulates CTLA-4: relevance for Sézary syndrome

Advances in research on potential inhibitors of multiple myeloma

Multiple myeloma (MM) is a common hematological malignancy. Although recent clinical applications of immunomodulatory drugs, proteasome inhibitors and CD38-targeting antibodies have significantly improved the outcome of MM patient with increased survival, the incidence of drug resistance and severe treatment-related complications is gradually on the rise. This review article summarizes the characteristics and clinical investigations of several MM drugs in clinical trials, including their structures, mechanisms of action, structure-activity relationships, and clinical study progress. Furthermore, the application potentials of the drugs that have not yet entered clinical trials are also reviewed. The review also outlines the future directions of MM drug development.

Proteostasis in T cell aging

Aging leads to a decline in immune cell function, which leaves the organism vulnerable to infections and age-related multimorbidities. One major player of the adaptive immune response are T cells, and recent studies argue for a major role of disturbed proteostasis contributing to reduced function of these cells upon aging. Proteostasis refers to the state of a healthy, balanced proteome in the cell and is influenced by synthesis (translation), maintenance and quality control of proteins, as well as degradation of damaged or unwanted proteins by the proteasome, autophagy, lysosome and cytoplasmic enzymes. This review focuses on molecular processes impacting on proteostasis in T cells, and specifically functional or quantitative changes of each of these upon aging. Importantly, we describe the biological consequences of compromised proteostasis in T cells, which range from impaired T cell activation and function to enhancement of inflamm-aging by aged T cells. Finally, approaches to improve proteostasis and thus rejuvenate aged T cells through pharmacological or physical interventions are discussed.

Pharmacologic targeting of Nedd8-activating enzyme reinvigorates T-cell responses in lymphoid neoplasia

Neddylation is a sequential enzyme-based process which regulates the function of E3 Cullin-RING ligase (CRL) and thus degradation of substrate proteins. Here we show that CD8+ T cells are a direct target for therapeutically relevant anti-lymphoma activity of pevonedistat, a Nedd8-activating enzyme (NAE) inhibitor. Pevonedistat-treated patient-derived CD8+ T cells upregulated TNFα and IFNγ and exhibited enhanced cytotoxicity. Pevonedistat induced CD8+ T-cell inflamed microenvironment and delayed tumor progression in A20 syngeneic lymphoma model. This anti-tumor effect lessened when CD8+ T cells lost the ability to engage tumors through MHC class I interactions, achieved either through CD8+ T-cell depletion or genetic knockout of B2M. Meanwhile, loss of UBE2M in tumor did not alter efficacy of pevonedistat. Concurrent blockade of NAE and PD-1 led to enhanced tumor immune infiltration, T-cell activation and chemokine expression and synergistically restricted tumor growth. shRNA-mediated knockdown of HIF-1α, a CRL substrate, abrogated the in vitro effects of pevonedistat, suggesting that NAE inhibition modulates T-cell function in HIF-1α-dependent manner. scRNA-Seq-based clinical analyses in lymphoma patients receiving pevonedistat therapy demonstrated upregulation of interferon response signatures in immune cells. Thus, targeting NAE enhances the inflammatory T-cell state, providing rationale for checkpoint blockade-based combination therapy.

The Value of Immunohistochemical Expression of TOX, ICOS, and GATA-3 in the Diagnosis of Mycosis Fungoides

BACKGROUND

Mycosis fungoides (MF) is considered the commonest type of cutaneous T-cell lymphoma representing about 50% of all primary cutaneous lymphomas. Differentiation between MF and another inflammatory dermatitis (BIDs) is important to ensure proper management.

AIM

We aimed to evaluate the immunohistochemical expression of T OX, ICOS, and GATA binding protein 3 (GATA-3) in early stages MF (stage IA and IB) to establish their diagnostic value and to guide the use of inhibitors in the treatment of cutaneous T-cell lymphomas.

MATERIALS AND METHODS

A retrospective study of 75 skin paraffin blocks (punch biopsy) 40 cases of MF and 35 cases of eczematous dermatitis as a group representing other inflammatory dermatitis were retrieved from archives of the pathology department of our University, during the period from October 2017 to May 2021.

RESULTS

About 98% and 90% of patients in the MF group had positive T OX and ICOS, while 70% of them had positive GATA-3. High expression of T OX, ICOS, and GATA-3 was associated with higher stages.

CONCLUSIONS

T OX is considered a diagnostic marker for early MF. The importance of identifying novel markers in MF expressed by immunohistochemistry, such as ICOS, has been established. According to our results, GATA-3 could be used as an accessory marker in the diagnosis of MF when combined with T OX and ICOS in a panel.

Potential of E3 Ubiquitin Ligases in Cancer Immunity: Opportunities and Challenges

Cancer immunotherapies, including immune checkpoint inhibitors and immune pathway–targeted therapies, are promising clinical strategies for treating cancer. However, drug resistance and adverse reactions remain the main challenges for immunotherapy management. The future direction of immunotherapy is mainly to reduce side effects and improve the treatment response rate by finding new targets and new methods of combination therapy. Ubiquitination plays a crucial role in regulating the degradation of immune checkpoints and the activation of immune-related pathways. Some drugs that target E3 ubiquitin ligases have exhibited beneficial effects in preclinical and clinical antitumor treatments. In this review, we discuss mechanisms through which E3 ligases regulate tumor immune checkpoints and immune-related pathways as well as the opportunities and challenges for integrating E3 ligases targeting drugs into cancer immunotherapy.

Multimodal single-cell analysis of cutaneous T-cell lymphoma reveals distinct subclonal tissue-dependent signatures

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous group of mature T-cell neoplasms characterized by the accumulation of clonal malignant CD4+ T cells in the skin. The most common variant of CTCL, mycosis fungoides (MF ), is confined to the skin in early stages but can be accompanied by extracutaneous dissemination of malignant T cells to the blood and lymph nodes in advanced stages of disease. Sézary syndrome (SS), a leukemic form of disease, is characterized by significant blood involvement. Little is known about the transcriptional and genomic relationship between skin- and blood-residing malignant T cells in CTCL. To identify and interrogate malignant clones in matched skin and blood from patients with leukemic MF and SS, we combine T-cell receptor clonotyping with quantification of gene expression and cell surface markers at the single cell level. Our data reveal clonal evolution at a transcriptional and genetic level within the malignant populations of individual patients. We highlight highly consistent transcriptional signatures delineating skin- and blood-derived malignant T cells. Analysis of these 2 populations suggests that environmental cues, along with genetic aberrations, contribute to transcriptional profiles of malignant T cells. Our findings indicate that the skin microenvironment in CTCL promotes a transcriptional response supporting rapid malignant expansion, as opposed to the quiescent state observed in the blood, potentially influencing efficacy of therapies. These results provide insight into tissue-specific characteristics of cancerous cells and underscore the need to address the patients' individual malignant profiles at the time of therapy to eliminate all subclones.

Neddylation and anti-tumor immunity

Contrary to chemotherapy, novel targeted therapies are associated with diverse immunomodulatory effects. Nedd8 is a small ubiquitin-like modifier that is involved in regulation of protein degradation. Neddylation is a promising target in cancer. Pevonedistat, a small molecule inhibitor of the Nedd8-activating enzyme, demonstrates pre-clinical activity in multiple tumor types. Recent studies have revealed that neddylation is important in immunity. We and others have shown that interfering with neddylation causes downstream immunomodulatory effects potentially leading to enhanced anti-tumor immunity. Thus, Nedd8 is a promising target in immuno-oncology.

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.

The immunopathogenesis and immunotherapy of cutaneous T cell lymphoma: Pathways and targets for immune restoration and tumor eradication

Cutaneous T cell lymphomas (CTCLs) are malignancies of skin-trafficking T cells. Patients with advanced CTCL manifest immune dysfunction that predisposes to infection and suppresses the antitumor immune response. Therapies that stimulate immunity have produced superior progression-free survival compared with conventional chemotherapy, reinforcing the importance of addressing the immune deficient state in the care of patients with CTCL. Recent research has better defined the pathogenesis of these immune deficits, explaining the mechanisms of disease progression and revealing potential therapeutic targets. The features of the malignant cell in mycosis fungoides and Sézary syndrome are now significantly better understood, including the T helper 2 cell phenotype, regulatory T cell cytokine production, immune checkpoint molecule expression, chemokine receptors, and interactions with the microenvironment. The updated model of CTCL immunopathogenesis provides understanding into clinical progression and therapeutic response.

Targeting the ubiquitination/deubiquitination process to regulate immune checkpoint pathways

The immune system initiates robust immune responses to defend against invading pathogens or tumor cells and protect the body from damage, thus acting as a fortress of the body. However, excessive responses cause detrimental effects, such as inflammation and autoimmune diseases. To balance the immune responses and maintain immune homeostasis, there are immune checkpoints to terminate overwhelmed immune responses. Pathogens and tumor cells can also exploit immune checkpoint pathways to suppress immune responses, thus escaping immune surveillance. As a consequence, therapeutic antibodies that target immune checkpoints have made great breakthroughs, in particular for cancer treatment. While the overall efficacy of immune checkpoint blockade (ICB) is unsatisfactory since only a small group of patients benefited from ICB treatment. Hence, there is a strong need to search for other targets that improve the efficacy of ICB. Ubiquitination is a highly conserved process which participates in numerous biological activities, including innate and adaptive immunity. A growing body of evidence emphasizes the importance of ubiquitination and its reverse process, deubiquitination, on the regulation of immune responses, providing the rational of simultaneous targeting of immune checkpoints and ubiquitination/deubiquitination pathways to enhance the therapeutic efficacy. Our review will summarize the latest findings of ubiquitination/deubiquitination pathways for anti-tumor immunity, and discuss therapeutic significance of targeting ubiquitination/deubiquitination pathways in the future of immunotherapy.

Immune Checkpoint Molecules-Inherited Variations as Markers for Cancer Risk

In recent years, immunotherapy has been revolutionized by a new approach that works by blocking receptors called immune checkpoints (IC). These molecules play a key role in maintaining immune homeostasis, mainly by suppressing the immune response and by preventing its overactivation. Since inhibition of the immune response by IC can be used by cancer to avoid recognition and destruction by immune system, blocking them enhances the anti-tumor response. This therapeutic approach has brought spectacular clinical effects. The ICs present heterogeneous expression patterns on immune cells, which may affect the effectiveness of immunotherapy. The inherited genetic variants in regulatory regions of ICs genes can be considered as potential factors responsible for observed inter-individual differences in ICs expression levels on immune cells. Additionally, polymorphism located in exons may introduce changes to ICs amino acid sequences with potential impact on functional properties of these molecules. Since genetic variants may affect both expression and structure of ICs, they are considered as risk factors of cancer development. Inherited genetic markers such as SNPs may also be useful in stratification patients into groups which will benefit from particular immunotherapy. In this review, we have comprehensively summarized the current understanding of the relationship between inherited variations of CTLA-4, PDCD1, PD-L1, BTLA, TIM-3, and LAG-3 genes in order to select SNPs which can be used as predictive biomarkers in personalized evaluation of cancer risk development and outcomes as well as possible response to immunotherapy.

The transcription factor Zfp281 sustains CD4+ T lymphocyte activation through directly repressing Ctla-4 transcription

The expression of coinhibitory receptors, such as CTLA-4, on effector T cells is a key mechanism for the negative regulation of T-cell activation. However, the transcriptional regulation of CTLA-4 is not well understood. Zfp281, a C2H2 zinc finger protein, is a negative regulator of pluripotency maintenance of embryonic stem cells. Nevertheless, the function of Zfp281 in differentiated cells has not been studied. We generated Zfp281 conditional knockout mice in which the function of the Zfp281 gene was conditionally disrupted by the Cd4Cre transgene to study its impact on T cell function. Zfp281 had no effect on T-cell development, but CD4+ T cell activation and cytokine production were impaired due to diminished T-cell receptor signaling. Furthermore, Zfp281 deficiency inhibited in vivo T cell responses to Listeria monocytogenes infection. Using genome-wide expression profiling assays, we determined that Zfp281 repressed Ctla-4 expression by directly binding to GC-rich sites in its promoter, which inhibited the negative feedback of T cell activation. In line with this result, CTLA-4 blockade and shRNA knockdown partly rescued the reduced cytokine production caused by Zfp281 deficiency. These findings indicate that Zfp281 sustains CD4+ T lymphocyte activation by directly repressing Ctla-4 transcription.

Gene Expression Comparison between Sézary Syndrome and Lymphocytic-Variant Hypereosinophilic Syndrome Refines Biomarkers for Sézary Syndrome

Sézary syndrome (SS), an aggressive cutaneous T-cell lymphoma (CTCL) with poor prognosis, is characterized by the clinical hallmarks of circulating malignant T cells, erythroderma and lymphadenopathy. However, highly variable clinical skin manifestations and similarities with benign mimickers can lead to significant diagnostic delay and inappropriate therapy that can lead to disease progression and mortality. SS has been the focus of numerous transcriptomic-profiling studies to identify sensitive and specific diagnostic and prognostic biomarkers. Benign inflammatory disease controls (e.g., psoriasis, atopic dermatitis) have served to identify chronic inflammatory phenotypes in gene expression profiles, but provide limited insight into the lymphoproliferative and oncogenic roles of abnormal gene expression in SS. This perspective was recently clarified by a transcriptome meta-analysis comparing SS and lymphocytic-variant hypereosinophilic syndrome, a benign yet often clonal T-cell lymphoproliferation, with clinical features similar to SS. Here we review the rationale for selecting lymphocytic-variant hypereosinophilic syndrome (L-HES) as a disease control for SS, and discuss differentially expressed genes that may distinguish benign from malignant lymphoproliferative phenotypes, including additional context from prior gene expression studies to improve understanding of genes important in SS.

Atypical BCL6/GATA3+ Primary Cutaneous Acral CD8-Positive T-Cell Lymphoma: A Diagnostic Challenge

ABSTRACT

Primary cutaneous acral CD8-positive T-cell lymphoma consists of slow-growing nodules in acral sites with a histopathology, suggesting high-grade lymphoma despite the indolent clinical course. It has been recently included in WHO-EORTC classification for primary cutaneous lymphomas as a provisional entity. A correct diagnosis of this entity is important because its differential diagnosis include more aggressive cutaneous lymphomas. We present a 53-year-old woman with an indolent solitary nodule on her right leg, which histopathologically showed features of CD8-positive T-cell lymphoma, although with some peculiarities, including epidermotropism, absence of CD68 expression, and positivity for GATA3 and Bcl6 in neoplastic cells. This case could contribute to better define the spectrum of this rare cutaneous lymphoma.

PDCD1 and PDCD1LG1 polymorphisms affect the susceptibility to multiple myeloma

Single-nucleotide polymorphisms (SNPs) of the programmed cell death protein-1 (PDCD1), programmed cell death protein-1 ligand-1 (PDCD1LG1), and cytotoxic T lymphocyte-associated antigen-4 (CTLA4) genes are implicated in the pathogenesis of some cancers. We investigated the role of PDCD1, PDCD1LG1, and CTLA4 SNPs in MM pathogenesis and the susceptibility to and clinical features of multiple myeloma (MM). We obtained genomic DNA from 124 patients with MM and 211 healthy controls and detected PDCD1 (rs36084323, rs41386349, and rs2227982), PDCD1LG1 (rs2297136 and rs4143815), and CTLA4 (rs733618, rs11571316, rs231775, and rs3087243) genotypes using the polymerase chain reaction-restriction fragment length polymorphism method or the TaqMan allelic discrimination real-time PCR method. The patients with MM had a significantly higher frequency of the PDCD1 GCC/GCC haplotype (rs36084323/rs41386349/rs2227982) compared with the healthy controls. PDCD1 rs2227982 CC genotype was associated significantly with a higher frequency of bone lesions. Patients with PDCD1LG1 rs2297136 TT and TC types (high-expression types) showed lower albumin level than those with CC genotype. In addition, the PDCD1LG1 rs4143815 CC and CG types (high-expression types) were associated significantly with higher frequency of patients who were treated with thalidomide and/or bortezomib. However, there was no statistical significance between CTLA4 polymorphisms and clinical variables of patients with MM. There were no significant differences between all the polymorphisms and OS. Our study indicates that the PDCD1 haplotype is associated with a susceptibility to MM. The PDCD1 rs2227982 and PDCD1LG1 rs2297136 affect the clinical features of multiple myeloma patients.

Regulation of Cancer Immune Checkpoint: Mono- and Poly-Ubiquitination: Tags for Fate

The antagonism, stalemate and compromise between the immune system and tumor cells is closely associated with tumor development and progression. In recent years, tumor immunotherapy has made continuous breakthroughs. It has become an important approach for cancer treatment, improving the survival and prognosis of more and more tumor patients. Further investigating the mechanism of tumor immune regulation, and exploring tumor immunotherapy targets with high specificity and wide applicability will provide researchers and clinicians with favorable weapons towards cancer. Ubiquitination affects protein fate through influencing the activity, stability and location of target protein. The regulation of substrate protein fate by ubiquitination is involved in cell cycle, apoptosis, transcriptional regulation, DNA repair, immune response, protein degradation and quality control. E3 ubiquitin ligase selectively recruits specific protein substrates through specific protein-protein interactions to determine the specificity of the overall ubiquitin modification reaction. Immune-checkpoint inhibitory pathway is an important mechanism for tumor cells to evade immune killing, which can inhibit T cell activity. Blocking the immune checkpoints and activating T cells through targeting the negative regulatory factors of T cell activation and removing the "brake" of T lymphocytes can enhance T cells immune response against tumors. Therefore, blocking the immune checkpoint is one of the methods to enhance the activity of T cells, and it is also a hot target for the development of anti-tumor drugs in recent years, whose inhibitors have shown good effect in specific tumor treatment. Ubiquitination, as one of the most important posttranslational modification of proteins, also modulates the expression, intracellular trafficking, subcellular and membranous location of immune checkpoints, regulating the immune surveillance of T cells to tumors.

miRNA‑135a regulates Hut78 cell proliferation via the GATA‑3/TOX signaling pathway

The present study investigated the role of microRNA‑135a (miR‑135a) in cutaneous T‑cell lymphoma (CTCL) proliferation. Compared with the normal T lymphocyte control cell line, the mRNA and protein levels of GATA binding protein 3 (GATA‑3) were markedly increased in the Hut78 cell line and miR‑135a was markedly decreased (P<0.05). Based on bioinformatics, the target gene of miR‑135a was identified as GATA‑3. Dual luciferase and pre‑miR‑135a assays showed that miR‑135a regulated the translation of GATA‑3. In addition, the overexpression of miR‑135a mimics decreased the protein levels of GATA‑3 and thymocyte selection‑associated high mobility group box (TOX). The substantially increased mRNA and protein levels of GATA‑3 may be associated with the downregulation of miR‑135a, leading to T‑cell deregulation and proliferation through GATA‑3/TOX regulation and subsequently causing CTCL.

New Therapies and Immunological Findings in Cutaneous T-Cell Lymphoma

Primary cutaneous lymphomas comprise a group of lymphatic malignancies that occur primarily in the skin. They represent the second most common form of extranodal non-Hodgkin’s lymphoma and are characterized by heterogeneous clinical, histological, immunological, and molecular features. The most common type is mycosis fungoides and its leukemic variant, Sézary syndrome. Both diseases are considered T-helper cell type 2 (Th2) diseases. Not only the tumor cells but also the tumor microenvironment can promote Th2 differentiation, which is beneficial for the tumor cells because a Th1 environment enhances antitumor immune responses. This Th2-dominant milieu also underlies the infectious susceptibility of the patients. Many components, such as tumor-associated macrophages, cancer-associated fibroblasts, and dendritic cells, as well as humoral factors, such as chemokines and cytokines, establish the tumor microenvironment and can modify tumor cell migration and proliferation. Multiagent chemotherapy often induces immunosuppression, resulting in an increased risk of serious infection and poor tolerance. Therefore, overtreatment should be avoided for these types of lymphomas. Interferons have been shown to increase the time to next treatment to a greater degree than has chemotherapy. The pathogenesis and prognosis of cutaneous T-cell lymphoma (CTCL) differ markedly among the subtypes. In some aggressive subtypes of CTCLs, such as primary cutaneous gamma/delta T-cell lymphoma and primary cutaneous CD8⁺ aggressive epidermotropic cytotoxic T-cell lymphoma, hematopoietic stem cell transplantation should be considered, whereas overtreatment should be avoided with other, favorable subtypes. Therefore, a solid understanding of the pathogenesis and immunological background of cutaneous lymphoma is required to better treat patients who are inflicted with this disease. This review summarizes the current knowledge in the field to attempt to achieve this objective.

Immune Checkpoint Inhibitors to Treat Malignant Lymphomas

Genetic and/or epigenetic changes provide antigen-derived diversity in neoplastic cells. Beside, these cells do not initiate immune response of host organisms. A variety of factors are responsible for the resistant to treatment, including individual variations in patients and somatic cell genetic differences in tumors, even those from the same tissue of origin. Immune system is controlled by several controlling mechanisms. Recently, a significant progress in hematologic treatment has been made; however, majority of diseases still remain incurable. Immunotherapy with checkpoint inhibitors has emerged as promising modality of antitumor treatment, showing marked response to several antigens, including cytotoxic T lymphocyte-associate protein-4 (CTLA-4) or programmed cell death 1 receptor (PD-1). In this review, we demonstrate actual knowledge on immune checkpoint function and its impact on development of new modality of antineoplastic treatment, using, for example, anti-CTLA-4 or PD-1/PD1 ligand (PD-L1) monoclonal antibodies in malignant lymphomas.

Checkpoint inhibitors in hematological malignancies

Inhibitory molecules such as PD-1, CTLA-4, LAG-3, or TIM-3 play a role to keep a balance in immune function. However, many cancers exploit such molecules to escape immune surveillance. Accumulating data support that their functions are dysregulated in lymphoid neoplasms, including plasma cell myeloma, myelodysplastic syndrome, and acute myeloid leukemia. In lymphoid neoplasms, aberrations in 9p24.1 (PD-L1, PD-L2, and JAK2 locus), latent Epstein-Barr virus infection, PD-L1 3'-untranslated region disruption, and constitutive JAK-STAT pathway are known mechanisms to induce PD-L1 expression in lymphoma cells. Clinical trials demonstrated that PD-1 blockade is an attractive way to restore host's immune function in hematological malignancies, particularly classical Hodgkin lymphoma. Numerous clinical trials exploring PD-1 blockade as a single therapy or in combination with other immune checkpoint inhibitors in patients with hematologic cancers are under way. Although impressive clinical response is observed with immune checkpoint inhibitors in patients with certain cancers, not all patients respond to immune checkpoint inhibitors. Therefore, to identify best candidates who would have excellent response to checkpoint inhibitors is of utmost importance. Several possible biomarkers are available, but consensus has not been made and pursuit to discover the best biomarker is ongoing.

MicroRNA-181 contributes to downregulation of SAMHD1 expression in CD4+ T-cells derived from Sèzary syndrome patients

Sézary syndrome (SS) is a rare subtype of cutaneous T-cell lymphoma (CTCL) that is characterized by aggressive spread of neoplastic CD4+ T-cells from the skin into the bloodstream with metastasis to visceral organs. The deoxynucleoside triphosphohydrolase SAMHD1 is highly expressed in normal CD4+ T-cells, while its expression is down-regulated in CD4+ T-cells from SS patients. MicroRNA (miR) dysregulation is an important epigenetic mechanism in the pathogenesis and progression of SS. MiR-181 has been shown to inhibit SAMHD1 expression in cell lines and was identified as an important prognostic biomarker in CTCL. However, whether SAMHD1 is down-regulated by miR-181 in primary CD4+ T-cells of SS patients is unknown. Compared to normal CD4+ T-cells, SAMHD1 protein expression is significantly reduced in transformed CD4+ T-cell lines and CD4+ T-cells from SS patients, which inversely correlates with increased miR-181 levels in these cells. Over-expression of miR-181b in primary CD4+ T-cells from healthy donors significantly decreased SAMHD1 protein level, but not mRNA level. In contrast, inhibition of miR-181 in a CD4+ T-cell line significantly increased the level of SAMHD1 protein expression. Our results demonstrate that miR-181 is an important regulator of SAMHD1 protein expression in neoplastic CD4+ T-cells, likely through a mechanism of translational inhibition.

TOX expression and role in CTCL

BACKGROUND

Cutaneous T-cell lymphomas (CTCL) are skin malignancies including mycosis fungoides (MF) and CD30(+) lymphoproliferative disorders (LPD). In early disease, CTCL can be difficult to diagnose, especially in MF for which there is no reliable diagnostic marker. MF/CTCL have increased expression of thymocyte selection-associated HMG box protein (TOX). Although TOX has been proposed to be a diagnostic marker for MF, further validation studies are needed. Moreover, it is unclear what drives TOX expression or its role in MF/CTCL.

OBJECTIVE

We hypothesize evaluation of TOX levels across a spectrum of CTCL, including MF precursor (large plaque parapsoriasis, LPP), will help elucidate the implications of altered TOX expression.

MATERIALS AND METHODS

TOX staining was performed in MF, CD30(+) LPD, LPP as well as benign inflammatory dermatoses (BID) and normal skin (NS). CTCL cell lines were utilized to evaluate the regulation of TOX.

RESULTS

Positive TOX expression was identified in 73.6% of MF cases and in 31.6% of BID/NS. TOX had a positive predictive value (PPV) for MF of 86.7% and a negative predictive value (NPV) of 48.1%. TOX expression in MF was detected more commonly in Black patients (P = 0.015) and less commonly in transformed MF (P = 0.045). LPP had positive TOX staining in 70.0%. In CTCL cells, GATA3 knockdown decreased TOX mRNA and protein expression. TOX expression also decreased in the presence of CTCL therapeutics.

CONCLUSION

Our data indicate that TOX is useful as a diagnostic marker in MF. Moreover, TOX expression was evident in LPP, indicating it may have a previously unappreciated role in the development of MF. Finally, our data suggest that GATA3 regulates TOX, revealing insight into TOX regulation.

Global intron retention mediated gene regulation during CD4+ T cell activation

T cell activation is a well-established model for studying cellular responses to exogenous stimulation. Using strand-specific RNA-seq, we observed that intron retention is prevalent in polyadenylated transcripts in resting CD4⁺ T cells and is significantly reduced upon T cell activation. Several lines of evidence suggest that intron-retained transcripts are less stable than fully spliced transcripts. Strikingly, the decrease in intron retention (IR) levels correlate with the increase in steady-state mRNA levels. Further, the majority of the genes upregulated in activated T cells are accompanied by a significant reduction in IR. Of these 1583 genes, 185 genes are predominantly regulated at the IR level, and highly enriched in the proteasome pathway, which is essential for proper T cell proliferation and cytokine release. These observations were corroborated in both human and mouse CD4⁺ T cells. Our study revealed a novel post-transcriptional regulatory mechanism that may potentially contribute to coordinated and/or quick cellular responses to extracellular stimuli such as an acute infection.

Sézary Syndrome and Atopic Dermatitis: Comparison of Immunological Aspects and Targets

Sézary syndrome (SS), an aggressive form of erythrodermic pruritic cutaneous T cell lymphoma (CTCL), from an immunological perspective characterized by increased Th2 cytokine levels, elevated serum IgE and impaired cellular immunity. Not only the clinical appearance but also the hallmark immunological characteristics of SS often share striking similarities with acute flares of atopic dermatitis (AD), a common benign chronic inflammatory skin disease. Given the overlap of several immunological features, the application of similar or even identical therapeutic approaches in certain stages of both diseases may come into consideration. The aim of this review is to compare currently accepted immunological aspects and possible therapeutic targets in AD and SS.

Induction of HER2 Immunity in Outbred Domestic Cats by DNA Electrovaccination

Domestic cats share human living environments and genetic traits. They develop spontaneous feline mammary carcinoma (FMC) with similar histopathology to human breast cancer. HER2 and AKT phosphorylation was demonstrated in primary FMC by immunoblot analysis, indicating HER2 as a therapeutic target. FMC lines K12 and K248 expressing HER1, HER2, and HER3 were sensitive to receptor tyrosine kinase (RTK) inhibitors gefitinib and lapatinib. To test HER2 vaccine response in cats, purpose-bred, healthy cats were electrovaccinated with heterologous (xenogeneic) or point-mutated feline HER2 DNA. T-cell reactivity to feline self-HER2 was detected in 4 of 10 cats that received bear HER2, human-rat fusion HER2 (E2Neu) or mutant feline HER2 (feHER2-K), which contains a single amino acid substitution. The variable T-cell responses may resemble that in the genetically heterogeneous human population. All immune sera to heterologous HER2 recognized feline HER2 expressed in 3T3 cells (3T3/HER2), but not that in FMC K12 or K248. Immune sera to mutant pfeHER2-K bound 3T3/HER2 cells weakly, but they showed better recognition of K12 and K248 cells that also express HER1 and HER3, suggesting distinct HER2 epitopes displayed by FMC that may be simulated by feHER2-K. In summary, HER2 DNA electroporation overcomes T-cell immune tolerance in approximately 40% of healthy cats and induces antibodies with distinct specificity. Vaccination studies in domestic cats can expedite vaccine iteration to guide human vaccine design and better predict outcome, with the added benefit of helping feline mammary tumor patients.

GATA3 in Breast Cancer: Tumor Suppressor or Oncogene?

GATA3 is a highly conserved, essential transcription factor expressed in a number of tissues, including the mammary gland. GATA3 expression is required for normal development of the mammary gland where it is estimated to be the most abundant transcription factor in luminal epithelial cells. In breast cancer, GATA3 expression is highly correlated with the luminal transcriptional program. Recent genomic analysis of human breast cancers has revealed high-frequency mutation in GATA3 in luminal tumors, suggesting "driver" function(s). Here we discuss mutation of GATA3 in breast cancer and the potential mechanism(s) by which mutation may lead to a growth advantage in cancer.

Pathology of T-cell lymphomas: diagnosis and biomarker discovery

T-cell lymphomas are a group of predominantly rare hematologic malignancies that tend to recapitulate different stages of T-cell development, in a similar way that B-cell lymphomas do. As opposed to B-cell lymphomas, the understanding of the biology and the classification of T-cell lymphomas are somewhat rudimentary, and numerous entities are still included as 'provisional categories' in the World Health Classification of hematolopoietic malignancies. A relevant and useful classification of these disorders have been difficult to accomplish because of the rarity nature of them, the relative lack of understanding of the molecular pathogenesis, and their morphological and immunophenotypical complexity. Overall, T-cell lymphomas represent only 15 % of all non-Hodgkin lymphomas. This review is focused on addressing the current status of the categories of mature T-cell leukemias and lymphomas (nodal and extranodal) using an approach that incorporates histopathology, immunophenotype, and molecular understanding of the nature of these disorders, using the same philosophy of the most recent revised WHO classification of hematopoietic malignancies.

Evidence of an oncogenic role of aberrant TOX activation in cutaneous T-cell lymphoma

TOX is a nuclear factor essential for the development of CD4(+) T cells in the thymus. It is normally expressed in low amounts in mature CD4(+) T cells of the skin and the peripheral blood. We have recently discovered that the transcript levels of TOX were significantly increased in mycosis fungoides, the most common type of cutaneous T-cell lymphoma (CTCL), as compared to normal skin or benign inflammatory dermatoses. However, its involvement in advanced CTCL and its biological effects on CTCL pathogenesis have not been explored. In this study, we demonstrate that TOX expression is also enhanced significantly in primary CD4(+)CD7(-) cells from patients with Sézary syndrome, a leukemic variant of CTCL, and that high TOX transcript levels correlate with increased disease-specific mortality. Stable knockdown of TOX in CTCL cells promoted apoptosis and reduced cell cycle progression, leading to less cell viability and colony-forming ability in vitro and to reduced tumor growth in vivo. Furthermore, TOX knockdown significantly increased 2 cyclin-dependent kinase (CDK) inhibitors, CDKN1B and CDKN1C. Lastly, blocking CDKN1B and CDKN1C reversed growth inhibition of TOX knockdown. Collectively, these findings provide strong evidence that aberrant TOX activation is a critical oncogenic event for CTCL.

Novel therapies for cutaneous T-cell lymphoma: what does the future hold?

INTRODUCTION

Cutaneous T-cell lymphomas (CTCLs) represent a group of extranodal non-Hodgkin lymphomas, of which mycosis fungoides (MF) is the most frequent. Standard therapeutic approaches are well established and often achieve stable disease. However, cure for MF is rare and thus novel therapies are needed.

AREAS COVERED

This review provides a discussion of the most promising new therapeutic approaches in the management of MF and other rare CTCLs. It includes targeted therapies with antibodies against surface molecules on malignant T cells (e.g., brentuximab), novel chemotherapeutic agents (e.g., pralatrexate), small-molecule compounds (e.g., panobinostat) and evidence of emerging targets in CTCLs (e.g., anti-IL-31). It also provides discussion of immune checkpoint inhibitors such as anti-PD1 that are worth considering in the treatment of leukaemic CTCL variants. Finally, it gives a brief overview of the possible use of stem-cell transplantation.

EXPERT OPINION

There is no doubt that progress has been made in the treatment of CTCLs with new, innovative and promising therapies approaching. However, there is still an urgent need to identify and test additional targets in well-designed clinical trials.