Staphylococcus aureus induces drug resistance in cancer T cells in Sézary syndrome.

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.

[Autoimmune bullous diseases in children]. / Dermatoses bulleuses auto-immunes chez les enfants.

Auto-immune bullous diseases (AIBD) are rare in children. Although their pathogenesis is similar to their adult counterpart, there are differences in the clinical presentation. Moreover certain AIBD prevail at certain ages. There are no guidelines for the treatment of AIBD specific for children. In this review the recent literature is summarised with attention to recent data including diagnostic criteria. We also propose a treatment algorithm.

Les maladies bulleuses auto-immunes (MBAI) sont rares chez les enfants. Bien que la pathogenèse soit similaire à celle de l'adulte, il existe des différences concernant la présentation clinique et la prévalence des MBAI selon l'âge. À ce jour, il n'y a pas de recommandations spécifiques pour leur prise en charge chez l'enfant. Dans cet article, nous présentons une revue des données actuelles, des critères diagnostiques et proposons un algorithme de prise en charge.

Two different types of tandem sequences mediate the overexpression of TinCYP51B in azole-resistant Trichophyton indotineae.

Trichophyton indotineae is an emerging dermatophyte that causes severe tinea corporis and tinea cruris. Numerous cases of terbinafine- and azole-recalcitrant T. indotineae-related dermatophytosis have been observed in India over the past decade, and cases are now being recorded worldwide. Whole genome sequencing of three azole-resistant strains revealed a variable number of repeats of a 2,404 base pair (bp) sequence encoding TinCYP51B in tandem specifically at the CYP51B locus position. However, many other resistant strains (itraconazole MIC ≥0.25 µg/mL; voriconazole MIC ≥0.25 µg/mL) did not contain such duplications. Whole-genome sequencing of three of these strains revealed a variable number of 7,374 bp tandem repeat blocks harboring TinCYP51B. Consequently, two types of T. indotineae azole-resistant strains were found to host TinCYP51B in tandem sequences (type I with 2,404 bp TinCYP51B blocks and type II with 7,374 bp TinCYP51B blocks). Using the CRISPR/Cas9 genome-editing tool, the copy number of TinCYP51B within the genome of types I and II strains was brought back to a single copy. The azole susceptibility of these modified strains was similar to that of strains without TinCYP51B duplication, showing that azole resistance in T. indotineae strains is mediated by one of two types of TinCYP51B amplification. Type II strains were prevalent among 32 resistant strains analyzed using a rapid and reliable PCR test.

Boost of innate immunity cytokines as biomarkers of response to extracorporeal photopheresis in patients with leukaemic cutaneous T-cell lymphoma.

BACKGROUND: Extracorporeal photopheresis (ECP) has emerged as a systemic first-line immunomodulatory therapy in leukaemic cutaneous T-cell lymphoma (L-CTCL) and is now beginning to be utilized in other T-cell-mediated diseases. Although ECP has been used for nearly 30 years, its mechanisms of action are not sufficiently understood, and biomarkers for response are scarce. OBJECTIVES: We aimed to investigate the immunomodulatory effects of ECP on cytokine secretion patterns in patients with L-CTCL, to help elucidate its mechanism of action. METHODS: A total of 25 patients with L-CTCL and 15 healthy donors (HDs) were enrolled in this retrospective cohort study. Concentrations of 22 cytokines were simultaneously quantified by using multiplex bead-based immunoassays. Neoplastic cells in patients' blood were evaluated by flow cytometry. RESULTS: Firstly, we observed a distinct cytokine profile pattern difference between L-CTCLs and HDs. There was a significant loss of tumour necrosis factor (TNF)-α, and significant increase of interleukins (IL)-9, IL-12 and IL-13 in the sera of patients with L-CTCL compared with HDs. Secondly, patients with L-CTCL who received ECP were classified as treatment responders and nonresponders according to the quantitative reduction of malignant burden in their blood. We evaluated cytokine levels in culture supernatants from patients' peripheral blood mononuclear cells (PBMCs) at baseline and 27 weeks after ECP initiation. Strikingly, PBMCs purified from ECP responders released statistically higher concentrations of innate immune cytokines IL-1α, IL-1ß, granulocyte-macrophage colony-stimulating factor (GM-CSF) and TNF-α in comparison with ECP nonresponders. In parallel, responders showed clearance of erythema, reduction of malignant clonal T cells in the blood, and a potent boost of relevant innate immune cytokines in individual patients with L-CTCL. CONCLUSIONS: Taken together, our results demonstrate that ECP stimulates the innate immune network, and facilitates redirection of the tumour-biased immunosuppressive microenvironment towards proactive antitumour immune responses. The alterations of IL-1α, IL-1ß, GM-CSF and TNF-α can be used as biomarkers of response to ECP in patients with L-CTCL.

Reliable and rapid identification of terbinafine resistance in dermatophytic nail and skin infections.

BACKGROUND: Fungal infections are the most frequent dermatoses. The gold standard treatment for dermatophytosis is the squalene epoxidase (SQLE) inhibitor terbinafine. Pathogenic dermatophytes resistant to terbinafine are an emerging global threat. Here, we determine the proportion of resistant fungal skin infections, analyse the molecular mechanisms of terbinafine resistance, and validate a method for its reliable rapid identification. METHODS: Between 2013 and 2021, we screened 5634 consecutively isolated Trichophyton for antifungal resistance determined by hyphal growth on Sabouraud dextrose agar medium containing 0.2 µg/mL terbinafine. All Trichophyton isolates with preserved growth capacity in the presence of terbinafine underwent SQLE sequencing. Minimum inhibitory concentrations (MICs) were determined by the broth microdilution method. RESULTS: Over an 8-year period, the proportion of fungal skin infections resistant to terbinafine increased from 0.63% in 2013 to 1.3% in 2021. Our routine phenotypic in vitro screening analysis identified 0.83% (n = 47/5634) of Trichophyton strains with in vitro terbinafine resistance. Molecular screening detected a mutation in the SQLE in all cases. Mutations L393F, L393S, F397L, F397I, F397V, Q408K, F415I, F415S, F415V, H440Y, or A398 A399 G400 deletion were detected in Trichophyton rubrum. Mutations L393F and F397L were the most frequent. In contrast, all mutations detected in T. mentagrophytes/T. interdigitale complex strains were F397L, except for one strain with L393S. All 47 strains featured significantly higher MICs than terbinafine-sensitive controls. The mutation-related range of MICs varied between 0.004 and 16.0 µg/mL, with MIC as low as 0.015 µg/mL conferring clinical resistance to standard terbinafine dosing. CONCLUSIONS: Based on our data, we propose MIC of 0.015 µg/mL as a minimum breakpoint for predicting clinically relevant terbinafine treatment failure to standard oral dosing for dermatophyte infections. We further propose growth on Sabouraud dextrose agar medium containing 0.2 µg/mL terbinafine and SQLE sequencing as fungal sporulation-independent methods for rapid and reliable detection of terbinafine resistance.

Pathogenesis and Therapy of Primary Cutaneous T-Cell Lymphoma: Collegium Internationale Allergologicum (CIA) Update 2020.

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous disease group of unknown etiology with a complex immunological background. As CTCL arises from T cells that have a vital role in the antitumor response, their therapy is largely aimed at reversing the immunological mechanisms leading to or manifesting during this malignancy. Early disease stages can be controlled with skin-directed therapy in most CTCL cases. Still, advanced CTCL has a dismal prognosis and warrants systemic therapy. Despite considerable progress in understanding the pathophysiology of the disease and the numerous systemic treatment options available, long-term remission rates with conventional treatments alone are still low. Allogeneic hematopoietic stem cell transplantation is currently the only curative option for advanced CTCL, including mycosis fungoides and Sézary syndrome. The aims of this review is to summarize the recent findings on the immunology of this heterogeneous disease and to present the advances in its clinical management.

Aggressive Rare T-cell Lymphomas with Manifestation in the Skin: A Monocentric Cross-sectional Case Study.

Rare T- or NK-cell lymphomas with cutaneous manifestation may display a highly aggressive clinical course and major diagnostic/therapeutic challenges. This report describes our experiences with different lymphomas of this rare category and the therapeutic options used. This retrospective, descriptive, monocentric, cross-sectional case study, identified 4 rare aggressive T-/NK-cell lymphomas with manifestation in the skin, which were diagnosed in a tertiary care centre over a period of 4 years. Two patients had an Epstein-Barr virus-associated extranodal NK/T-cell lymphoma and 2 patients had a primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma. Concomitant extracutaneous involvement was observed in 2 of all 4 patients. Two patients had fulminant disease progression and resistance to chemotherapy. Two patients underwent allogeneic haematopoietic stem cell transplantation, which resulted in one complete remission and one partial remission. This report emphasizes the importance of an early diagnostic work-up and a prompt aggressive therapeutic approach.

Expression of Programmed Cell Death Protein 1 by Tumor-Infiltrating Lymphocytes and Tumor Cells is Associated with Advanced Tumor Stage in Patients with Esophageal Adenocarcinoma.

BACKGROUND: Despite recent advances in the therapy for adenocarcinoma of the esophagogastric junction (AEG), overall prognosis remains poor. Programmed cell death protein 1 (PD1) is a co-inhibitory receptor primarily expressed by T-cells. Tumor cells can escape anticancer immune responses by triggering the PD1 pathway. Moreover, PD1 receptor engagement on cancer cells may trigger tumor-intrinsic growth signals. This study aimed to evaluate the potential clinical relevance of PD1 expression by tumor-infiltrating lymphocytes (TILs) and cancer cells in the AEG. METHODS: Patients with AEG who underwent esophagectomy from 1992 to 2011 were included in the study. Expression of PD1was evaluated by immunohistochemistry and correlated with long-term overall survival (OS), disease-free survival (DFS), and various clinicopathologic parameters. RESULTS: Tumor biospecimens from 168 patients were analyzed. In the analysis, 81% of the patients showed high tumoral frequencies (>5%) of PD1-expressing TILs (TIL-PD1+), and 77% of patient tumors harbored high levels (>5%) of PD1+ cancer cells (cancer-PD1+). Expression of PD1 by TILs and cancer cells correlated significantly (p < 0.05) with patients' tumor stage and lymph node involvement. Compared with the patients who had low tumoral frequencies of PD1+ TILs or cancer cells, the TIL-PD1+ and cancer-PD1+ patients demonstrated significantly reduced DFS in the univariate analysis (5-year DFS: 73.3 vs. 41.9%, log-rank 0.008 and 71.3 vs. 41.6%, p = 0.008, respectively). Additionally, the cancer-PD1+ patients showed significantly decreased OS in the univariate analysis compared with the cancer-PD1- patients (5-year OS: 68.8 vs. 43.5%; p = 0.047). However, these correlations did not reach significance in the multivariate analysis. CONCLUSIONS: The PD1 receptor is expressed by both TILs and cancer cells in AEG. High expression of PD1 is associated with advanced tumor stage and lymph node involvement, but not with survival.

Expression of CD164 on Malignant T cells in Sézary Syndrome.

Sézary syndrome is a primary cutaneous T-cell lymphoma characterized by pruritic erythroderma, peripheral lymphadenopathy and the presence of malignant T cells in the blood. Unequivocal detection of malignant cells in patients with Sézary syndrome is of important diagnostic, prognostic and therapeutic value. However, no single Sézary syndrome specific cell surface marker has been identified. In a cohort of patients with Sézary syndrome, CD164 expression on total CD4+ lymphocytes was significantly upregulated compared with healthy controls. CD164 expression was in most cases limited to CD4+CD26- malignant T lymphocytes, unequivocally identified using flow-cytometry by the expression of a specific Vß clone for each patient. Increased expression of CD164 may be a promising diagnostic parameter and a potential target for a CD164-linked therapeutic approach in Sézary syndrome.

MHC-I upregulation safeguards neoplastic T cells in the skin against NK cell-mediated eradication in mycosis fungoides.

Cancer-associated immune dysfunction is a major challenge for effective therapies. The emergence of antibodies targeting tumor cell-surface antigens led to advancements in the treatment of hematopoietic malignancies, particularly blood cancers. Yet their impact is constrained against tumors of hematopoietic origin manifesting in the skin. In this study, we employ a clonality-supervised deep learning methodology to dissect key pathological features implicated in mycosis fungoides, the most common cutaneous T-cell lymphoma. Our investigations unveil the prominence of the IL-32ß-major histocompatibility complex (MHC)-I axis as a critical determinant in tumor T-cell immune evasion within the skin microenvironment. In patients' skin, we find MHC-I to detrimentally impact the functionality of natural killer (NK) cells, diminishing antibody-dependent cellular cytotoxicity and promoting resistance of tumor skin T-cells to cell-surface targeting therapies. Through murine experiments in female mice, we demonstrate that disruption of the MHC-I interaction with NK cell inhibitory Ly49 receptors restores NK cell anti-tumor activity and targeted T-cell lymphoma elimination in vivo. These findings underscore the significance of attenuating the MHC-I-dependent immunosuppressive networks within skin tumors. Overall, our study introduces a strategy to reinvigorate NK cell-mediated anti-tumor responses to overcome treatment resistance to existing cell-surface targeted therapies for skin lymphoma.

Th17-associated cytokines IL-17 and IL-23 in inflamed skin of Darier disease patients as potential therapeutic targets.

Darier disease (DD) is a rare, inherited multi-organ disorder associated with mutations in the ATP2A2 gene. DD patients often have skin involvement characterized by malodorous, inflamed skin and recurrent, severe infections. Therapeutic options are limited and inadequate for the long-term management of this chronic disease. The aim of this study was to characterize the cutaneous immune infiltrate in DD skin lesions in detail and to identify new therapeutic targets. Using gene and protein expression profiling assays including scRNA sequencing, we demonstrate enhanced expression of Th17-related genes and cytokines and increased numbers of Th17 cells in six DD patients. We provide evidence that targeting the IL-17/IL-23 axis in a case series of three DD patients with monoclonal antibodies is efficacious with significant clinical improvement. As DD is a chronic, relapsing disease, our findings might pave the way toward additional options for the long-term management of skin inflammation in patients with DD.

Increased Chlormethine-Induced DNA Double-Stranded Breaks in Malignant T Cells from Mycosis Fungoides Skin Lesions.

Mycosis fungoides (MF) is a type of cutaneous T-cell lymphoma. Chlormethine (CL) is recommended as first-line therapy for MF, with a major purpose to kill tumor cells through DNA alkylation. To study the extent of treatment susceptibility and tumor specificity, we investigated the gene expression of different DNA repair pathways, DNA double-stranded breaks, and tumor cell proliferation of clonal TCR Vß+ tumor cell populations in cutaneous T-cell lymphoma skin cells on direct exposure to CL. Healthy human T cells were less susceptible to CL exposure than two T-lymphoma cell lines, resulting in higher proportions of viable cells. Interestingly, in T cells from MF lesions, we observed a downregulation of several important DNA repair pathways, even complete silencing of RAD51AP1, FANC1, and BRCA2 involved in homologous recombination repair. In the presence of CL, the double-stranded DNA breaks in malignant MF skin T cells increased significantly as well as the expression of the apoptotic gene CASP3. These data point toward an important effect of targeting CL on MF skin tumor T cells, which support CL use as an early cutaneous lymphoma treatment and can be of synergistic use, especially beneficial in the setting of combination skin-directed therapies for cutaneous T-cell lymphoma.

Identification of Dermatophyte and Non-Dermatophyte Agents in Onychomycosis by PCR and DNA Sequencing-A Retrospective Comparison of Diagnostic Tools.

Rapid and reliable fungal identification is crucial to delineate infectious diseases, and to establish appropriate treatment for onychomycosis. Compared to conventional diagnostic methods, molecular techniques are faster and feature higher accuracy in fungal identification. However, in current clinical practice, molecular mycology is not widely available, and its practical applicability is still under discussion. This study summarizes the results of 16,094 consecutive nail specimens with clinical suspicion of onychomycosis. We performed PCR/sequencing on all primary nail specimens for which conventional mycological diagnostics remained inconclusive. In specimens with a positive direct microscopy but negative or contaminated culture, molecular mycology proved superior and specified a fungal agent in 65% (587/898). In 75% (443/587), the identified pathogen was a dermatophyte. Positive cultures for dermatophytes, yeasts and non-dermatophyte molds (NDMs) were concordant with primary-specimen-DNA PCR/sequencing in 83% (10/12), 34% (22/65) and 45% (76/169), respectively. Among NDMs, agreement was high for Fusarium spp. (32/40; 80%), but low for Penicillium spp. (5/25; 20%) and Alternaria spp. (1/20; 5%). This study underlines the improvement in diagnostic yield by fungal primary-specimen-DNA PCR/sequencing in the event of a negative or contaminated culture, as well as its significance for the diagnosis of dermatophyte and non-dermatophyte onychomycosis. Molecular mycology methods like PCR and DNA sequencing should complement conventional diagnostics in cases of equivocal findings, suspected NDM onychomycosis or treatment-resistant nail pathologies.

Cytotoxic CD8α+ leucocytes have heterogeneous features in antigen recognition and class I MHC restriction in grouper.

CD8 is a membrane glycoprotein found primarily on the surface of T lymphocytes such as cytotoxic T lymphocytes (CTL), natural killer cells (NK) and γδ T lymphocytes. It helps T lymphocytes to kill the infected cells that presents microbial antigen on the cell surface. However, analysis of fish cellular immunity has been limited because of the lack of CD8 antibodies in grouper. In this present study, we cloned full-length CD8α cDNAs from orange-spotted grouper (Epinephelus coioides), an important fish species economically. The deduced protein of CD8α contained 227 amino acid residues in length and included one signal peptide, Ig superfamily V domain, hinge region, transmembrane domain, cytoplasmic tail and conserved binding motif associated with tyrosine kinase p56(lck). The molecular weight of the mature protein was estimated at 22.5 kDa and pI at 9.55. Phylogenetically, the predicted grouper CD8α protein was similar to CD8α from other marine fish species in which the identity was 50-60%. Real-time PCR revealed that CD8α transcript was constitutively expressed in thymus, head kidney, gill, spleen, gut and peripheral blood leucocyte (PBL); and the highest expression in thymus. CD8α transcript in the spleen of fish injected with nervous necrosis virus (NNV) was significantly up-regulated at 4 days post-injection compared to the untreated fish. Rabbit antiserum prepared against recombinant CD8α protein was able to recognize specifically the subset lymphocytes which have a diameter of 7 µm, a high nucleus/cytoplasm ratio and a ring-shaped cytoplasm. The cytotoxicity of CD8α(+) lymphocytes at one-week post-NNV infection was enhanced significantly against NNV-infected autologous fin cells in comparison with NNV-infected allogeneic or RSIV-infected autologous fin cells. Flow cytometry analysis revealed that both the number and mean fluorescence intensity (MFI) of CD8α(+) PBL were significantly increased at 7 days post-NNV infection. The specific cytotoxicity and MHC class I restriction of the lymphocytes sorted by rCD8α antibody are properties that can be attributed to CTL. In addition, low level of cytotoxicity was found in PBL against allogeneic targets as well as CD8α(+) effectors killed autologous targets nonspecifically, implicated presence of cytotoxic T subsets, possibly nonspecific cytotoxic cells (NCC) and γδ T lymphocytes, without MHC class I restriction. In conclusion, grouper cytotoxic CD8α(+) PBL have heterogeneous features in specific antigen recognition and class I MHC restriction.

A weakly supervised deep learning approach for label-free imaging flow-cytometry-based blood diagnostics.

The application of machine learning approaches to imaging flow cytometry (IFC) data has the potential to transform the diagnosis of hematological diseases. However, the need for manually labeled single-cell images for machine learning model training has severely limited its clinical application. To address this, we present iCellCnn, a weakly supervised deep learning approach for label-free IFC-based blood diagnostics. We demonstrate the capability of iCellCnn to achieve diagnosis of Sézary syndrome (SS) from patient samples on the basis of bright-field IFC images of T cells obtained after fluorescence-activated cell sorting of human peripheral blood mononuclear cell specimens. With a sample size of four healthy donors and five SS patients, iCellCnn achieved a 100% classification accuracy. As iCellCnn is not restricted to the diagnosis of SS, we expect such weakly supervised approaches to tap the diagnostic potential of IFC by providing automatic data-driven diagnosis of diseases with so-far unknown morphological manifestations.

Enhancement of antibody-dependent cellular cytotoxicity is associated with treatment response to extracorporeal photopheresis in Sézary syndrome.

Sézary syndrome (SS) is a rare, leukemic type of cutaneous T-cell lymphoma (CTCL), for which extracorporeal photopheresis (ECP) is a first-line therapy. Reliable biomarkers to objectively monitor the response to ECP in patients with SS are missing. We examined the quantitative and qualitative impact of ECP on natural killer (NK) cell activity in SS patients, and especially their functional ability for antibody-dependent cell-mediated cytotoxicity (ADCC). Further, we addressed the question whether the magnitude of the effect on ADCC can be associated with the anti-cancer efficacy of ECP in SS patients. We assessed numbers of NK cells, ADCC activity, and treatment response based on blood tumor staging in a cohort of 13 SS patients (8 women, 5 men) treated with ECP as a first-line therapy. Blood samples were collected before treatment start and after an average of 9 months of uninterrupted ECP treatment. NK cell numbers were reduced in SS patients compared to healthy individuals and showed a tendency of recovery after long-term ECP treatment, independent of the clinical response to treatment. Patients with marginal increase (≤1.5 AU-fold) or lack of increase in ADCC activity failed to respond clinically to treatment, while patients with an increased ADCC activity showed a reduction in blood tumor burden. NK-mediated ADCC is selectively enhanced and might be a mechanism underlying the effect of ECP while in addition it can possibly serve as a reliable biomarker to objectively monitor response to ECP in patients with SS.

mRNA-Based Anti-TCR CDR3 Tumour Vaccine for T-Cell Lymphoma.

Efficient vaccination can be achieved by injections of in vitro transcribed mRNA (ivt mRNA) coding for antigens. This vaccine format is particularly versatile and allows the production of individualised vaccines conferring, T-cell immunity against specific cancer mutations. The CDR3 hypervariable regions of immune receptors (T-cell receptor, TCR or B-cell receptor, BCR) in the context of T- or B-cell leukaemia or lymphoma are targetable and specific sequences, similar to cancer mutations. We evaluated the functionality of an mRNA-based vaccine designed to trigger immunity against TCR CDR3 regions in an EL4 T-lymphoma cell line-derived murine in vivo model. Vaccination against the hypervariable TCR regions proved to be a feasible approach and allowed for protection against T-lymphoma, even though immune escape in terms of TCR downregulation paralleled the therapeutic effect. However, analysis of human cutaneous T-cell lymphoma samples indicated that, as is the case in B-lymphomas, the clonotypic receptor may be a driver mutation and is not downregulated upon treatment. Thus, vaccination against TCR CDR3 regions using customised ivt mRNA is a promising immunotherapy method to be explored for the treatment of patients with T-cell lymphomas.

Selective inhibition of HDAC6 sensitizes cutaneous T-cell lymphoma to PI3K inhibitors.

Histone deacetylase (HDAC) inhibitors, approved for the treatment of cutaneous T-cell lymphoma (CTCL), are non-selective agents associated with an unsatisfactory response and considerable side-effects. Targeting single HDAC isoforms is considered to provide novel therapeutic options. HDAC6 is overexpressed in primary samples from patients with CTCL and preclinical studies using transgenic mice that spontaneously develop a CTCL-like disease, have suggested that combinations including HDAC6 inhibitors may be successful in the treatment of CTCL. PI3K inhibition is currently being tested in clinical trials for CTCL with promising results. Since HDAC6 is known to diminish the activity of Akt via its deacetylation, the aim of the present study was to evaluate the therapeutic potential of selective HDAC6 inhibitors in combination with PI3K inhibitors in CTCL. Through the genetic and pharmacological inhibition of HDAC6, it was demonstrated that combining HDAC6 with PI3K inhibition may be an attractive therapeutic option for patients with CTCL.

Blockade of programmed cell death protein 1 (PD-1) in Sézary syndrome reduces Th2 phenotype of non-tumoral T lymphocytes but may enhance tumor proliferation.

Sézary syndrome (SS) is an aggressive leukemic variant of cutaneous T-cell lymphoma (L-CTCL) that arises from malignant clonally derived skin-homing CD4+ T cells. Based on advancements in our understanding of the mechanisms underlying L-CTCL, boosting the suppressed immune response emerges as a promising strategy in SS management. Immune checkpoint inhibitory molecules have already demonstrated efficacy in a wide spectrum of malignancies. Currently, agents targeting the programmed death-1 (PD-1) axis are under evaluation in L-CTCL. Here we investigated the expression of PD-1 and its ligands, PD-L1 and PD-L2 in blood and skin from patients with L-CTCL. We demonstrate that PD-1 expression is markedly increased on tumor T cells compared to non-tumor CD4+ T cells from SS patients and to CD4+ cells from healthy individuals. In contrast, PD-L1 shows decreased expression on tumor T cells, while PD-L2 expression is low without significant differences between these groups. Functional PD-1 blockade in vitro resulted in reduced Th2 phenotype of non-tumor T lymphocytes, but enhanced the proliferation of tumor T cells from SS patients. Our study sheds some light on the PD-1 axis in both peripheral blood and skin compartments in SS patients, which may be relevant for the treatment of L-CTCL with immune checkpoint inhibitor.