Search

Abstract: Patients with Sézary syndrome (SS), a leukemic variant of cutaneous T-cell lymphoma (CTCL), are prone to Staphylococcus aureus infections and have a poor prognosis due to treatment resistance. Here, we report that S aureus and staphylococcal enterotoxins (SE) induce drug resistance in malignant T cells against therapeutics commonly used in CTCL. Supernatant from patient-derived, SE-producing S aureus and recombinant SE significantly inhibit cell death induced by histone deacetylase (HDAC) inhibitor romidepsin in primary malignant T cells from patients with SS. Bacterial killing by engineered, bacteriophage-derived, S aureus-specific endolysin (XZ.700) abrogates the effect of S aureus supernatant. Similarly, mutations in major histocompatibility complex (MHC) class II binding sites of SE type A (SEA) and anti-SEA antibody block induction of resistance. Importantly, SE also triggers resistance to other HDAC inhibitors (vorinostat and resminostat) and chemotherapeutic drugs (doxorubicin and etoposide). Multimodal single-cell sequencing indicates T-cell receptor (TCR), NF-κB, and JAK/STAT signaling pathways (previously associated with drug resistance) as putative mediators of SE-induced drug resistance. In support, inhibition of TCR-signaling and Protein kinase C (upstream of NF-κB) counteracts SE-induced rescue from drug-induced cell death. Inversely, SE cannot rescue from cell death induced by the proteasome/NF-κB inhibitor bortezomib. Inhibition of JAK/STAT only blocks rescue in patients whose malignant T-cell survival is dependent on SE-induced cytokines, suggesting 2 distinct ways SE can induce drug resistance. In conclusion, we show that S aureus enterotoxins induce drug resistance in primary malignant T cells. These findings suggest that S aureus enterotoxins cause clinical treatment resistance in patients with SS, and antibacterial measures may improve the outcome of cancer-directed therapy in patients harboring S aureus., (© 2024 American Society of Hematology. Published by Elsevier Inc. Licensed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0), permitting only noncommercial, nonderivative use with attribution. All other rights reserved.)

Staphylococcus aureus is suspected to fuel disease activity in cutaneous T-cell lymphomas. In this study, we investigate the effect of a recombinant, antibacterial protein, endolysin (XZ.700), on S. aureus skin colonization and malignant T-cell activation. We show that endolysin strongly inhibits the proliferation of S. aureus isolated from cutaneous T-cell lymphoma skin and significantly decreases S. aureus bacterial cell counts in a dose-dependent manner. Likewise, ex vivo colonization of both healthy and lesional skin by S. aureus is profoundly inhibited by endolysin. Moreover, endolysin inhibits the patient-derived S. aureus induction of IFNγ and the IFNγ-inducible chemokine CXCL10 in healthy skin. Whereas patient-derived S. aureus stimulates activation and proliferation of malignant T cells in vitro through an indirect mechanism involving nonmalignant T cells, endolysin strongly inhibits the effects of S. aureus on activation (reduced CD25 and signal transducer and activator of transcription 5 phosphorylation) and proliferation (reduced Ki-67) of malignant T cells and cell lines in the presence of nonmalignant T cells. Taken together, we provide evidence that endolysin XZ.700 inhibits skin colonization, chemokine expression, and proliferation of pathogenic S. aureus and blocks their potential tumor-promoting effects on malignant T cells., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Cutaneous T-cell lymphoma (CTCL) is a devastating lymphoid malignancy characterized by the accumulation of malignant T cells in the dermis and epidermis. Skin lesions cause serious symptoms that hamper quality of life and are entry sites for bacterial infection, a major cause of morbidity and mortality in advanced diseases. The mechanism driving the pathological processes that compromise the skin barrier remains unknown. Here, we report increased transepidermal water loss and compromised expression of the skin barrier proteins filaggrin and filaggrin-2 in areas adjacent to TOX-positive T cells in CTCL skin lesions. Malignant T cells secrete mediators (including cytokines such as interleukin 13 [IL-13], IL-22, and oncostatin M) that activate STAT3 signaling and downregulate filaggrin and filaggrin-2 expression in human keratinocytes and reconstructed human epithelium. Consequently, the repression of filaggrins can be counteracted by a cocktail of antibodies targeting these cytokines/receptors, small interfering RNA-mediated knockdown of JAK1/STAT3, and JAK1 inhibitors. Notably, we show that treatment with a clinically approved JAK inhibitor, tofacitinib, increases filaggrin expression in lesional skin from patients with mycosis fungoides. Taken together, these findings indicate that malignant T cells secrete cytokines that induce skin barrier defects via a JAK1/STAT3-dependent mechanism. As clinical grade JAK inhibitors largely abrogate the negative effect of malignant T cells on skin barrier proteins, our findings suggest that such inhibitors provide novel treatment options for patients with CTCL with advanced disease and a compromised skin barrier., (© 2023 by The American Society of Hematology.)

Staphylococcal enterotoxins are believed to fuel disease activity in cutaneous T-cell lymphoma. Recent data support this by showing that antibiotics inhibit malignant T cells in skin lesions in mycosis fungoides and Sézary syndrome, the most common forms of cutaneous T-cell lymphoma. Yet, it remains incompletely characterized how staphylococcal enterotoxins fuel disease activity. In this study, we show that staphylococcal enterotoxins induce the expression of the oncogenic microRNA miR-155 in primary malignant T cells. Thus, staphylococcal enterotoxins and Staphyloccocus aureus isolates from lesional skin of patients induce miR-155 expression at least partly through the IL-2Rg‒Jak‒signal transducer and activator of transcription 5 pathway, and the effect is augmented by the presence of nonmalignant T cells. Importantly, mycosis fungoides lesions harbor S. aureus, express Y-phosphorylated signal transducer and activator of transcription 5, and display enhanced miR-155 expression, when compared with nonlesional and healthy skin. Preliminary data show that aggressive antibiotic therapy is associated with decreased Y-phosphorylated signal transducer and activator of transcription 5 and miR-155 expression in lesional skin in two patients with Sézary syndrome. In conclusion, we show that S. aureus and its enterotoxins induce enhanced expression of oncogenic miR-155, providing mechanistic insight into the role of S. aureus in cutaneous T-cell lymphoma. Our findings support that environmental stimuli such as bacteria can fuel disease progression in cutaneous T-cell lymphoma., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: The thioredoxin-interacting protein (TXNIP) is involved in cellular metabolism and cell proliferation, and recently, deficient expression of TXNIP has been associated with progression and poor outcome for cancer patients., Objectives: To assess TXNIP expression and function in malignant T cells from cutaneous T-cell lymphoma (CTCL)., Methods: CTCL-derived malignant (MyLa2059, PB2B) and non-malignant (MyLa1850) cell lines were analysed by Western blotting and qPCR for TXNIP expression. Subsequently, the malignant CTCL cell lines were treated with GSK126 - an inhibitor of enhancer of zeste homolog 2 (EZH2) methyltransferase activity or assessed by bisulphite sequencing for TXNIP promoter methylation. Methylation was also assessed with the demethylating agent 5-azacytidine (5AZA). Finally, TXNIP was overexpressed in the malignant PB2B cell line via plasmid transduction, and the effect of TXNIP was further analysed by flow cytometry., Results: We report on low expression of TXNIP protein in all cell lines representing different subtypes and stages of CTCL when compared to non-malignant T cells. Epigenetic silencing and other mechanisms were involved in the repression of TXNIP whereas forced expression of TXNIP strongly inhibited proliferation of malignant T cells., Conclusions: Epigenetic silencing and other as yet unknown mechanisms repress TXNIP expression in malignant T cells. As forced expression of TXNIP inhibits malignant proliferation, we propose that TXNIP is a putative tumour suppressor in CTCL., (© 2020 S. Karger AG, Basel.)

Staphylococcus aureus and its toxins have been linked to disease progression and mortality in advanced stages of cutaneous T-cell lymphoma (CTCL). CD8 + T cells play a crucial role in anti-cancer responses and high CD8 + T cell numbers in tumor lesions are associated with a favorable prognosis in CTCL. Here, we show that CD8 + T cells from both healthy donors and Sézary syndrome patients are highly susceptible to cell death induced by Staphylococcal alpha-toxin, whereas malignant T cells are not. Importantly, alpha-toxin almost completely blocks cytotoxic killing of CTCL tumor cells by peptide-specific CD8 + T cells, leading to their escape from induced cell death and continued proliferation. These findings suggest that alpha-toxin may favor the persistence of malignant CTCL cells in vivo by inhibiting CD8 + T cell cytotoxicity. Thus, we propose a novel mechanism by which colonization with Staphylococcus aureus may contribute to cancer immune evasion and disease progression in CTCL., (© 2020 The Author(s). Published with license by Taylor & Francis Group, LLC.)

Background: The voltage-gated potassium channel Kv1.3 (KCNA3) is expressed by effector memory T cells (TEM) and plays an important role in their activation and proliferation. Mycosis fungoides (MF), the most common subtype of cutaneous T-cell lymphoma (CTCL), was recently proposed to be a malignancy of skin-resident TEM. However, the expression of Kv1.3 in CTCL has not been investigated., Objectives: This study aims to examine the expression of Kv1.3 in situ and in vitro in CTCL., Methods: The expression of Kv1.3 was examined by immunohistochemistry in skin lesions from 38 patients with MF, 4 patients with Sézary syndrome (SS), and 27 patients with benign dermatosis. In 4 malignant T-cell lines of CTCL (Myla2059, PB2B, SeAx, and Mac2a) and a non-malignant T-cell line (MyLa1850), the expression of Kv1.3 was determined by flow cytometry. The proliferation of those cell lines treated with various concentrations of Kv1.3 inhibitor ShK was measured by 3H-thymdine incorporation., Results: Half of the MF patients (19/38) displayed partial Kv1.3 expression including 1 patient with moderate Kv1.3 positivity, while the other half (19/38) exhibited Kv1.3 negativity. An almost identical distribution was observed in patients with benign conditions, that is, 44.4% (12/27) were partially positive for Kv1.3 including 1 patient with moderate Kv1.3 positivity, while 55.6% (15/27) were Kv1.3 negative. In contrast, 3 in 4 SS patients displayed partial Kv1.3 positivity including 2 patients with weak staining and 1 with moderate staining, while 1 in 4 SS patients was Kv1.3 negative. In addition, all malignant T-cell lines, and a non-malignant T-cell line, displayed low Kv1.3 surface expression with a similar pattern. Whereas 2 cell lines (PB2B and Mac2a) were sensitive to Kv1.3 blockade, the other 2 (Myla2059 and SeAx) were completely resistant., Conclusions: We provide the first evidence of a heterogeneous Kv1.3 expression in situ in CTCL lesions., (© 2019 S. Karger AG, Basel.)

It has been proposed that CD4 T-cell responses to Staphylococcus aureus (SA) can inadvertently enhance neoplastic progression in models of skin cancer and cutaneous T-cell lymphoma (CTCL). In this prospective study, we explored the effect of transient antibiotic treatment on tumor cells and disease activity in 8 patients with advanced-stage CTCL. All patients experienced significant decrease in clinical symptoms in response to aggressive, transient antibiotic treatment. In some patients, clinical improvements lasted for more than 8 months. In 6 of 8 patients, a malignant T-cell clone could be identified in lesional skin, and a significant decrease in the fraction of malignant T cells was observed following antibiotics but an otherwise unchanged treatment regimen. Immunohistochemistry, global messenger RNA expression, and cell-signaling pathway analysis indicated that transient aggressive antibiotic therapy was associated with decreased expression of interleukin-2 high-affinity receptors (CD25), STAT3 signaling, and cell proliferation in lesional skin. In conclusion, this study provides novel evidence suggesting that aggressive antibiotic treatment inhibits malignant T cells in lesional skin. Thus, we provide a novel rationale for treatment of SA in advanced CTCL.

B-lymphoid tyrosine kinase (BLK) is a non-receptor tyrosine kinase belonging to the SRC family kinases. BLK is known to be functionally involved in B-cell receptor signaling and B-cell development. New evidence suggests that B-lymphoid tyrosine kinase is ectopically expressed and is a putative oncogene in cutaneous T-cell lymphoma and other T-cell malignancies. However, little is known about the role of BLK in lymphomagenesis, and the oncogenic function seems to depend on the cellular context. Importantly, BLK is also ectopically expressed in other hematological and multiple non-hematological malignancies including breast, kidney, and lung cancers, suggesting that BLK could be a new potential target for therapy. Here, we studied the oncogenic potential of human BLK. We found that engrafted Ba/F3 cells stably expressing constitutive active human BLK formed tumors in mice, whereas neither Ba/F3 cells expressing wild type BLK nor non-transfected Ba/F3 cells did. Inhibition of BLK with the clinical grade and broadly reacting SRC family kinase inhibitor dasatinib inhibited growth of BLK-induced tumors. In conclusion, our study provides evidence that human BLK is a true proto-oncogene capable of inducing tumors, and we demonstrate a novel BLK activity-dependent tumor model suitable for studies of BLK-driven lymphomagenesis and screening of novel BLK inhibitors in vivo.

In cutaneous T cell lymphomas (CTCL), miR-21 is aberrantly expressed in skin and peripheral blood and displays anti-apoptotic properties in malignant T cells. It is, however, unclear exactly which cells express miR-21 and what mechanisms regulate miR-21. Here, we demonstrate miR-21 expression in situ in both malignant and reactive lymphocytes as well as stromal cells. qRT-PCR analysis of 47 patients with mycosis fungoides (MF) and Sezary Syndrome (SS) confirmed an increased miR-21 expression that correlated with progressive disease. In cultured malignant T cells miR-21 expression was inhibited by Tofacitinib (CP-690550), a clinical-grade JAK3 inhibitor. Chromatin immunoprecipitation (ChIP) analysis showed direct binding of STAT5 to the miR-21 promoter. Cytokine starvation ex vivo triggered a decrease in miR-21 expression, whereas IL-2 induced an increased miR-21 expression in primary SS T cells and cultured cytokine-dependent SS cells (SeAx). siRNA-mediated depletion of STAT5 inhibited constitutive- and IL-2-induced miR-21 expression in cytokine-independent and dependent T cell lines, respectively. IL-15 and IL-2 were more potent than IL-21 in inducing miR-21 expression in the cytokine-dependent T cells. In conclusion, we provide first evidence that miR-21 is expressed in situ in CTCL skin lesions, induced by IL-2 and IL-15 cytokines, and is regulated by STAT5 in malignant T cells. Thus, our data provide novel evidence for a pathological role of IL-2Rg cytokines in promoting expression of the oncogenic miR-21 in CTCL., Competing Interests: The authors declare no conflicts of interest.

Aberrant activation of Janus kinase-3 (Jak3) and its key down-stream effectors, Signal Transducer and Activator of Transcription-3 (STAT3) and STAT5, is a key feature of malignant transformation in cutaneous T-cell lymphoma (CTCL). However, it remains only partially understood how Jak3/STAT activation promotes lymphomagenesis. Recently, non-coding microRNAs (miRNAs) have been implicated in the pathogenesis of this malignancy. Here, we show that (i) malignant T cells display a decreased expression of a tumor suppressor miRNA, miR-22, when compared to non-malignant T cells, (ii) STAT5 binds the promoter of the miR-22 host gene, and (iii) inhibition of Jak3, STAT3, and STAT5 triggers increased expression of pri-miR-22 and miR-22. Curcumin, a nutrient with anti-Jak3 activity and histone deacetylase inhibitors (HDACi) also trigger increased expression of pri-miR-22 and miR-22. Transfection of malignant T cells with recombinant miR-22 inhibits the expression of validated miR-22 targets including NCoA1, a transcriptional co-activator in others cancers, as well as HDAC6, MAX, MYCBP, PTEN, and CDK2, which have all been implicated in CTCL pathogenesis. In conclusion, we provide the first evidence that de-regulated Jak3/STAT3/STAT5 signalling in CTCL cells represses the expression of the gene encoding miR-22, a novel tumor suppressor miRNA.

Patients with cutaneous T-cell lymphoma (CTCL) are frequently colonized with Staphylococcus aureus (SA). Eradication of SA is, importantly, associated with significant clinical improvement, suggesting that SA promotes the disease activity, but the underlying mechanisms remain poorly characterized. Here, we show that SA isolates from involved skin express staphylococcal enterotoxins (SEs) that induce crosstalk between malignant and benign T cells leading to Stat3-mediated interleukin-10 (IL-10) production by the malignant T cells. The SEs did not stimulate the malignant T cells directly. Instead, SEs triggered a cascade of events involving cell-cell and asymmetric cytokine interactions between malignant and benign T cells, which stimulated the malignant T cells to express high levels of IL-10. Much evidence supports that malignant activation of the Stat3/IL-10 axis plays a key role in driving the immune dysregulation and severe immunodeficiency that characteristically develops in CTCL patients. The present findings thereby establish a novel link between SEs and immune dysregulation in CTCL, strengthening the rationale for antibiotic treatment of colonized patients with severe or progressive disease., (© 2014 by The American Society of Hematology.)

Skin lesions from mycosis fungoides (MF) patients display an increased expression of interleukin-15 (IL-15), IL-17F, and other cytokines implicated in inflammation and malignant cell proliferation in cutaneous T-cell lymphoma (CTCL). In the leukemic variant of CTCL, Sézary syndrome (SS), IL-2 and IL-15 trigger activation of the Jak-3/STAT3 pathway and transcription of IL17A gene, whereas it is unknown what causes IL-15 expression, Jak3/STAT3 activation, and production of IL-17F in MF. Here, we studied the expression and regulation of IL-15 and its relation to IL-17F in MF cell lines and skin lesions from 60 MF patients. We show that: (1) the spontaneous IL-15 mRNA expression is resistant to Jak3 and STAT3 inhibitors at concentrations that profoundly inhibit STAT3 activation and IL-17F mRNA expression; (2) anti-IL-15 antibody blocks STAT3 activation induced by exogenous IL-15 in non-malignant MF T cells, whereas the spontaneous STAT3 activation and IL-17F expression in malignant T cells is not inhibited; (3) patients display heterogeneous IL-15/IL-17F mRNA expression patterns in skin lesions; and (4) IL-15 expression (in contrast to IL-17F) is not associated with progressive disease. Taken together, these findings indicate that IL-15 and IL-17F are differentially regulated and expressed in MF. We propose that IL-15 and IL-17F are markers for different inflammatory environments and play distinct roles in the development and progression of MF.

In patients with cutaneous T-cell lymphoma (CTCL) bacterial infections constitute a major clinical problem caused by compromised skin barrier and a progressive immunodeficiency. Indeed, the majority of patients with advanced disease die from infections with bacteria, e.g., Staphylococcus aureus. Bacterial toxins such as staphylococcal enterotoxins (SE) have long been suspected to be involved in the pathogenesis in CTCL. Here, we review links between bacterial infections and CTCL with focus on earlier studies addressing a direct role of SE on malignant T cells and recent data indicating novel indirect mechanisms involving SE- and cytokine-driven cross-talk between malignant- and non-malignant T cells.

Inappropriately regulated expression of interleukin (IL)-17A is associated with the development of inflammatory diseases and cancer. However, little is known about the role of other IL-17 family members in carcinogenesis. Here, we show that a set of malignant T-cell lines established from patients with cutaneous T-cell lymphoma (CTCL) spontaneously secrete IL-17F and that inhibitors of Janus kinases and Signal transducer and activator of transcription 3 are able to block that secretion. Other malignant T-cell lines produce IL-17A but not IL-17F. Upon activation, however, some of the malignant T-cell lines are able to coexpress IL-17A and IL-17F, leading to formation of IL-17A/F heterodimers. Clinically, we demonstrate that IL-17F messenger RNA expression is significantly increased in CTCL skin lesions compared with healthy donors and patients with chronic dermatitis. IL-17A expression is also increased and a significant number of patients express high levels of both IL-17A and IL-17F. Concomitantly, we observed that the expression of the IL-17 receptor is significantly increased in CTCL skin lesions compared with control subjects. Importantly, analysis of a historic cohort of 60 CTCL patients indicates that IL-17F expression is associated with progressive disease. These findings implicate IL-17F in the pathogenesis of CTCL and suggest that IL-17 cytokines and their receptors may serve as therapeutic targets.