Improved Sézary cell detection and novel insights into immunophenotypic and molecular heterogeneity in Sézary syndrome

Computational Flow Cytometry Accurately Identifies Sezary Cells Based on Simplified Aberrancy and Clonality Features

Flow cytometric identification of circulating neoplastic cells (Sezary cells) in patients with mycosis fungoides and Sezary syndrome is essential for diagnosis, staging, and prognosis. Although recent advances have improved the performance of this laboratory assay, the complex immunophenotype of Sezary cells and overlap with reactive T cells demand a high level of analytic expertise. We utilized machine learning to simplify this analysis using only 2 predefined Sezary cell-gating plots. We studied 114 samples from 59 patients with Sezary syndrome/mycosis fungoides and 66 samples from unique patients with inflammatory dermatoses. A single dimensionality reduction plot highlighted all TCR constant β chain-restricted (clonal) CD3+/CD4+ T cells detected by expert analysis. On receiver operator curve analysis, an aberrancy scale feature computed by comparison with controls (area under the curve = 0.98) outperformed loss of CD2 (0.76), CD3 (0.83), CD7 (0.77), and CD26 (0.82) in discriminating Sezary cells from reactive CD4+ T cells. Our results closely mirrored those obtained by exhaustive expert analysis for event classification (positive percentage agreement = 100%, negative percentage agreement = 99%) and Sezary cell quantitation (regression slope = 1.003, R squared = 0.9996). We demonstrate the potential of machine learning to simplify the accurate identification of Sezary cells.

Pathophysiology of cutaneous T-cell lymphomas: Perspective from a French referral centre

Cutaneous T-cell lymphomas (CTCL) are a diverse group of malignant blood disorders characterized by initial skin infiltration, and sometimes, tumor spreading to lymph nodes, blood, and viscera. Mycosis fungoides is the most common form. Sézary syndrome is a distinctive form of CTCL marked by a significant presence of circulating tumor cells in peripheral blood. These diseases are characterized by the plasticity and heterogeneity of the tumor cells in the different tissue compartments, and a difficulty in identifying these tumor cells for diagnostic purposes and therapeutic monitoring. Progress has been made in the understanding of the pathophysiology of these diseases in recent years, and we provide here a review of these advancements.

Delving into the Metabolism of Sézary Cells: A Brief Review

Primary cutaneous lymphomas (PCLs) are a heterogeneous group of lymphoproliferative disorders caused by the accumulation of neoplastic T or B lymphocytes in the skin. Sézary syndrome (SS) is an aggressive and rare form of cutaneous T cell lymphoma (CTCL) characterized by an erythroderma and the presence of atypical cerebriform T cells named Sézary cells in skin and blood. Most of the available treatments for SS are not curative, which means there is an urgent need for the development of novel efficient therapies. Recently, targeting cancer metabolism has emerged as a promising strategy for cancer therapy. This is due to the accumulating evidence that metabolic reprogramming highly contributes to tumor progression. Genes play a pivotal role in regulating metabolic processes, and alterations in these genes can disrupt the delicate balance of metabolic pathways, potentially contributing to cancer development. In this review, we discuss the importance of targeting energy metabolism in tumors and the currently available data on the metabolism of Sézary cells, paving the way for potential new therapeutic approaches aiming to improve clinical outcomes for patients suffering from SS.

As serious as Sézary

Sézary syndrome is a rare condition, with a very poor prognosis. This case highlights how important it is for clinicians to be cognizant of the impact that this condition and the various treatment regimens can have on patients’ lives.

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-32β-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.

Combining local cryoablation with PD-L1 blockade synergistically eradicates established murine lung cancer by modulating mitochondrial in PD-1+CD8+ T cell

Immune checkpoint blockade (ICB) has shown improvement in overall survival for lung cancer in clinical trials. However, monotherapies have limited efficacy in improving outcomes and benefit only a subset of patients. Combination therapies targeting multiple pathways can augment an immune response to improve survival further. Here, we demonstrate that combinatorial anti-PD-L1/cryoablation therapy generated a synergistic antitumor activity in the established lung cancer model. Importantly, it was observed that this favorable antitumor immune response comes predominantly from the PD-1+CD8+ T cells generated after the combination therapy, referred as improvement of IFN-γ production and mitochondrial metabolism, which resembled highly functional effectors CD8+ T cells. Notably, the cellular levels of mitochondrial reactive oxygen and mitochondria mass excessively coincided with alteration of IFN-γ secretion in PD-1+CD8+T cell subset. So far, anti-PD-L1/cryoablation therapy selectively derived the improvement of depolarized mitochondria in PD-1+CD8+T cell subset, subsequently rebuild the anti-tumor function of the exhausted CD8+ T cells. Collectively, there is considerable interest in anti-PD-L1 plus cryoablation combination therapy for patients with lung cancer, and defining the underlying mechanisms of the observed synergy.

What Is New in Cutaneous T Cell Lymphoma?

PURPOSE OF REVIEW

This review focuses on updates in prognosis, pathogenesis, and treatment of cutaneous T cell lymphoma (CTCL).

RECENT FINDINGS

Cohort studies indicate imaging may be necessary in early-stage CTCL. Risk factors for progression of CTCL have been identified. Interactions between malignant cells and the tumor microenvironment (TME) and the skin microbiome advance the understanding of pathogenesis and tumor cell dissemination. Studies support a hypothesis of circulating malignant tumor cells. MicroRNA (miR) influence tumor progression and prognosis; the IL22-STAT3-CCL20 cascade may be a novel target. IL-4, IL-5, and IL-31 cytokines are relevant for pruritus and could be targets for therapeutic interventions. Systemic therapies, such as JAK inhibitors, targeted antibodies, and checkpoint inhibitors, show promise in advanced stages. Allogenic hematopoietic stem cell transplantation provides a potential curative option for patients. Further investigations of prognosis and translational research are necessary to improve stratification of patients for treatment.

Die Wirkung von Mogamulizumab auf die aberrante T-Zell-Population im peripheren Blut - eine monozentrische retrospektive Analyse

Hintergrund

Die Wirkung von Mogamulizumab bei kutanen T‐Zell‐Lymphomen (CTCL) auf die T‐Zellen (TZ) im peripheren Blut und deren potenzielle Rolle bei der Steuerung von Behandlungsintervallen wird noch erforscht.

Methodik

Wir untersuchten in einer retrospektiven monozentrischen Analyse die Wirkung von Mogamulizumab auf die CD3+ TZ und die aberrante T‐Zellpopulation (TZP), CD4+/CD7– und die CD4+/CD26– TZ, die mittels Durchflusszytometrie analysiert wurden.

Ergebnisse

Dreizehn Patienten mit CTCL wurden eingeschlossen. Nach vier Zyklen kam es zu einer durchschnittlichen Reduktion der CD3+ TZ um 57%, der CD4+/CD7− um 72% und der CD4+/CD26− TZ um 75% im Vergleich zum individuellen Ausgangswert eines jeden Patienten. Die Reduktionen der CD4+/CD7+ und CD4+/CD26+ TZ fielen mit durchschnittlich 54% und 41% geringer aus. Ein signifikanter Rückgang der aberranten TZP war bereits nach der ersten Infusion zu beobachten. Ein medianes Plateau der TZP trat bereits während der Induktionsphase ein. Bei 5/13 Patienten kam es zu einem Progress der Erkrankung, ohne dass eine eindeutige Korrelation mit der aberranten TZP bestand.

Schlussfolgerungen

Bereits nach einer Gabe Mogamulizumab reduzierte sich die aberrante TZP und – in geringerem Maße – die normale TZP. Wir konnten keine eindeutige Korrelation der TZP mit der Wirksamkeit von Mogamulizumab beobachten. Es werden weitere Untersuchungen mit einer größeren Anzahl von Patienten benötigt.

The effect of mogamulizumab on the aberrant T cell population in the peripheral blood - A monocentric retrospective analysis

BACKGROUND AND OBJECTIVES

The effect of mogamulizumab in cutaneous T-cell lymphoma (CTCL) on T cells (TC) in the peripheral blood and its potential role to navigate treatment intervals are explored.

METHODS

We investigated within a retrospective monocentric analysis the effect of mogamulizumab on the CD3+ TC and the aberrant T cell population (TCP), i.e., the CD4+ /CD7- and the CD4+ /CD26- TC, analyzed by flow cytometry.

RESULTS

Thirteen patients with CTCL were included. After four cycles there was a mean reduction of 57% in CD3+ TC, 72% in the CD4+ /CD7- and 75% in the CD4+ /CD26- TCP compared to the individual baseline of each patient. The reduction in CD4+ /CD7+ and CD4+ /CD26+ TC was lower, averaging 54% and 41%. A significant decrease in aberrant TCP was already evident after the first administration. A median plateau of TCP already occurred during the IP. Progressive disease occurred in 5/13 patients without a clear correlation to aberrant TCP.

CONCLUSIONS

Already after one dose of mogamulizumab, aberrant TCP and, to a lesser extent, normal TC decrease. We did not observe a clear correlation between TCP and the efficacy of mogamulizumab, but further studies with larger numbers of patients are needed.

Imbalanced IL-1B and IL-18 Expression in Sézary Syndrome

Sézary syndrome (SS) is a rare and aggressive type of cutaneous T-cell lymphoma, with an abnormal inflammatory response in affected skin. The cytokines IL-1B and IL-18, as key signaling molecules in the immune system, are produced in an inactive form and cleave to the active form by inflammasomes. In this study, we assessed the skin, serum, peripheral mononuclear blood cell (PBMC) and lymph-node samples of SS patients and control groups (healthy donors (HDs) and idiopathic erythroderma (IE) nodes) to investigate the inflammatory markers IL-1B and IL-18 at the protein and transcript expression levels, as potential markers of inflammasome activation. Our findings showed increased IL-1B and decreased IL-18 protein expression in the epidermis of SS patients; however, in the dermis layer, we detected increased IL-18 protein expression. In the lymph nodes of SS patients at advanced stages of the disease (N2/N3), we also detected an enhancement of IL-18 and a downregulation of IL-1B at the protein level. Moreover, the transcriptomic analysis of the SS and IE nodes confirmed the decreased expression of IL1B and NLRP3, whereas the pathway analysis indicated a further downregulation of IL1B-associated genes. Overall, the present findings showed compartmentalized expressions of IL-1B and IL-18 and provided the first evidence of their imbalance in patients with Sézary syndrome.

Phenotypic plasticity of malignant T cells in blood and skin of a Sézary syndrome patient revealed by single cell transcriptomics

Background

Sézary Syndrome (SS) is an aggressive leukemic variant of cutaneous T-cell lymphomas (CTCL). In SS patients, malignant T cells are circulating through the blood and cause erythroderma.

Objective

To compare the transcriptome of single cells in blood and skin samples from a patient with advanced SS.

Methods

We utilized combined single cell RNA and T-cell receptor (TCR) sequencing (scRNA-seq).

Results

We scrutinized the malignant T cells in blood and skin in an unbiased manner without pre-sorting of cells. We observed different phenotypes of the same monoclonal malignant T-cell population, confirmed by TCR sequencing and inferred copy number variation analysis. Malignant T cells present in the circulating blood expressed genes resembling central memory T cells such as CCR7, IL7R and CD27. In the skin, we detected two major malignant T-cell populations: One subpopulation was closely related to the malignant T cells from the blood, while the other subpopulation expressed genes reminiscent of skin resident effector memory T cells including GZMB and NKG7. Pseudotime analysis indicated crucial transcriptomic changes in the transition of malignant T cells between blood and skin. These changes included the differential regulation of TXNIP, a putative tumor suppressor in CTCL, and the adaptation to the hypoxic conditions in the skin. Tumor cell proliferation in the skin was supported by stimulating interactions between myeloid cells and malignant T cells.

Conclusions

Using scRNA-seq we detected a high degree of functional heterogeneity within the malignant T-cell population in SS and highlighted crucial differences between SS cells in blood and skin.

Single-cell RNA-sequencing reveals predictive features of response to pembrolizumab in Sézary syndrome

The PD-1 inhibitor pembrolizumab is effective in treating Sézary syndrome, a leukemic variant of cutaneous T-cell lymphoma. Our purpose was to investigate the effects of pembrolizumab on healthy and malignant T cells in Sézary syndrome and to discover characteristics that predict pembrolizumab response. Samples were analyzed before and after 3 weeks of pembrolizumab treatment using single-cell RNA-sequencing of 118,961 peripheral blood T cells isolated from six Sézary syndrome patients. T-cell receptor clonotyping, bulk RNA-seq signatures, and whole-exome data were integrated to classify malignant T-cells and their underlying subclonal heterogeneity. We found that responses to pembrolizumab were associated with lower KIR3DL2 expression within Sézary T cells. Pembrolizumab modulated Sézary cell gene expression of T-cell activation associated genes. The CD8 effector populations included clonally expanded populations with a strong cytotoxic profile. Expansions of CD8 terminal effector and CD8 effector memory T-cell populations were observed in responding patients after treatment. We observed intrapatient Sézary cell heterogeneity including subclonal segregation of a coding mutation and copy number variation. Our study reveals differential effects of pembrolizumab in both malignant and healthy T cells. These data support further study of KIR3DL2 expression and CD8 immune populations as predictive biomarkers of pembrolizumab response in Sézary syndrome.

Single-cell analyses reveal novel molecular signatures and pathogenesis in cutaneous T cell lymphoma

Sézary syndrome (SS) is a rare and aggressive type of cutaneous T cell lymphoma (CTCL) with a poor prognosis. Intra-tumoral heterogeneity caused by different disease compartments (e.g., skin, blood) and poor understanding of the pathogenesis has created obstacles to the precise diagnosis and targeted treatment of the disease. Here we performed a comprehensive analysis by integrating single-cell transcriptomic data of 40,333 peripheral blood mononuclear cells (PBMCs) and 41,580 skin cells, as well as single-cell chromatin accessibility data of 11,058 PBMCs from an SS patient and matched healthy controls (HCs). Validation and functional investigation were carried out in an independent cohort consisting of SS patients, mycosis fungoides (MF) patients, psoriatic erythroderma patients, and HCs, as well as multiple cell lines. The analysis revealed that skin-derived Sézary cells (SCs) had a shifting trend to more advanced mature phenotypes compared to blood-derived SCs. A series of specific marker genes (TOX, DNM3, KLHL42, PGM2L1, and SESN3) shared in blood- and skin-derived SCs were identified, facilitating the diagnosis and prognosis of MF/SS. Moreover, luciferase reporter assays and gene knockdown assays were used to verify that KLHL42 was transcriptionally activated by GATA3 in SS. Functional assays indicated that KLHL42 silencing significantly inhibited aggressive CTCL cell proliferation and promoted its apoptosis. Therefore, targeting inhibition KLHL42 might serve as a promising therapeutic approach in CTCL.

[New insights into the pathogenesis and molecular understanding of cutaneous T-cell lymphomas]

The pathogenesis of cutaneous T‑cell lymphomas (CTCL) is still an enigma. Therefore, extensive translational research efforts have been undertaken in recent years to gain further clinical and molecular insights. There is increasing evidence that the different clinical appearance of the CTCL subtypes derives from the assumption that they develop from different skin subpopulations of T cells. Detection and quantification of the malignant T‑cell clones is crucial for the diagnosis and prognosis of CTCL. Numerous recurrent mutant cellular signalling pathways have been found in recent years. This includes the JAK-STAT, NFκB, T‑cell receptor and MAP kinase signalling pathways, as well as cell cycle control and epigenetics. The most recent analyses imply a tumour evolution model with initial copy number variation, like amplification or deletions of specific DNA fragments (CNVs) and only subsequent later single nucleotide variations (SNVs). The crucial question, however, is which CNVs are sufficient to initiate general tumourigenesis? The challenge is to identify possible driver genes. Increasing molecular understanding in CTCL will include new breakthrough therapeutic options in the near future.

T cells in the skin: lymphoma and inflammatory skin disease

T cells are established contributors to the pathogenesis of atopic dermatitis (AD) and psoriasis, yet whether they are the key drivers or simply unwitting participants remains incompletely understood. Conversely, malignant T cells are the undisputed culprits of cutaneous T cell lymphoma (CTCL), a group of diseases that share key clinical, histopathological and molecular features with inflammatory skin disease (ISD). Here, we compare the pathogenesis of ISD and CTCL and discuss the resulting insights. Recurrent, skin-limited disease implicates skin-resident T cells (T_RM) in both ISD and CTCL. In CTCL, malignant T cells recruit benign T cells into inflammatory skin lesions, a disease-amplifying function also proposed for pathogenic T cells in ISD. Mechanistically, cytokines produced by malignant T cells in CTCL and by pathogenic T cells in ISD, respectively, are likely both necessary and sufficient to drive skin inflammation and pruritus, which in turn promotes skin barrier dysfunction and dysbiosis. Therapies for ISD target T cell effector functions but do not address the chronicity of disease while treatments for CTCL target malignant T cells but not primarily the symptoms of the disease. By integrating our understanding of ISD and CTCL, important insights into pathogenesis and therapy can be made which may improve the lives of sufferers of both disease groups.

CD38 Expression by Circulating and Skin-Infiltrating Lymphocytes from Sezary Syndrome Patients: A Flow Cytometry and Immunohistochemistry Study

Background

Reports on the expression of CD38 in Sézary syndrome (SS), erythrodermic primary cutaneous T cell lymphoma with leukemic involvement, are limited. The aim of the present study is the analysis of the expression of CD38 by skin-infiltrating mononuclear cells and circulating T lymphocytes in a cohort of SS patients.

Methods

SS patients diagnosed since 1985 in our clinic were retrospectively analyzed for CD38 expression in biopsy and blood samples by immunohistochemistry and flow cytometry, respectively.

Results

SS patients show a predominant CD38-negative phenotype on both skin and blood. A subgroup of patients was found expressing CD38 (12 cases) in either the skin (>25% cell infiltrate) or blood (CD4+CD38+ >50%), among whom 4 in the blood, 7 in the skin, and 1 in both blood and skin.

Conclusion

The implications of these observations may be twofold: the relevance in basic science is related to a potential role in immune defense regulation, whilst in perspective CD38 may become a target for antibody therapy, considering the availability of different anti-CD38 monoclonal antibodies.

Flow cytometry for the assessment of blood tumour burden in cutaneous T-cell lymphoma: towards a standardised approach

Mycosis fungoides (MF) and Sézary syndrome (SS) are the best-studied subtypes of cutaneous T-cell lymphoma, a rare non-Hodgkin lymphoma that primarily presents in the skin but can also involve blood, lymph nodes, and viscera. The role of blood involvement in the assessment and staging of MF and SS has evolved in recent years from being classed as simply 'present' or 'absent', with no impact on staging, to full analysis of abnormal peripheral-blood T cells using flow cytometry (FC) to detect and quantify aberrant T-cell phenotypes and polymerase chain reaction (PCR) to characterise T-cell receptor gene rearrangements. These sensitive peripheral-blood assessments are replacing manual Sézary cell counts and have become an important part of clinical work-up in MF and SS, providing the potential for more accurate prognostication and appropriate management. However, although international recommendations now include guidelines for FC analysis of peripheral-blood markers for staging purposes, many clinics only perform these analyses in advanced-stage patients, if at all, and there is still a need for standardised use of validated markers. Standardisation of a single effective multiparameter FC panel would allow for accurate identification and quantification of blood tumour burden for diagnosis, staging, assessment of therapeutic response, and monitoring of disease progression at all stages of disease. Once defined, validation of an MF/SS biomarker FC panel will enable uptake into clinical settings along with associated standardisation of protocols and reagents. This review discusses the evolution of the role of FC in evaluating blood involvement in MF and SS, considers recently published international guidelines, and identifies evidence gaps for future research that will allow for standardisation of FC in MF and SS.

Mogamulizumab induces long term immune restoration and reshapes tumor heterogeneity in Sézary syndrome

BACKGROUND

Mogamulizumab, an anti-CCR4 monoclonal antibody, has been shown to increase progression-free survival in cutaneous T-cell lymphoma.

OBJECTIVES

We hypothesized that besides the targeted depletion of Sézary cells (SCs), mogamulizumab may reshape the immune tumor microenvironment.

METHODS

Both malignant and benign compartments from 26 Sézary patients with B2 stage before mogamulizumab initiation were prospectively analyzed using KIR3DL2 and TCR-Vβ markers, serological markers and molecular assessments of clonality.

RESULTS

Prior to mogamulizumab, the benign subset of CD4+ T-cells displayed exhausted phenotypes, with an increased gradient in PD1/TIGIT/DNAM/CD27/CD28 and CD70 expression from age- matched controls to patient benign CD4+T cells and to SCs. All patients presented SCs with heterogeneous phenotypes and differential expression of individual markers were found within distinct malignant subsets. Early complete blood response was observed in 17/26 patients and was associated to a higher baseline CCR4 expression. A drastic decrease in benign T cells and activated Treg counts was observed during the first 4 weeks. Long-term follow-up revealed the emergence of an immune restoration involving CD8+, naive and stem-memory CD4+T cells, with almost complete disappearance of exhausted lymphocytes. Development of resistance/tumor escape to mogamulizumab was associated to the emergence of CCR4- SCs in blood and skin, displaying significant changes in their heterogeneity patterns, and not univocally explained by mutations within CCR4 coding regions.

CONCLUSIONS

Mogamulizumab is likely contributing to the restoration of an efficient immunity and reshapes not only the malignant lymphocyte subset but also the benign subset. These results have potential implications for optimal therapeutic sequences and/or combinations.

Malignant and Benign T Cells Constituting Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma (CTCL) is a heterogeneous group of non-Hodgkin lymphoma, including various clinical manifestations, such as mycosis fungoides (MF) and Sézary syndrome (SS). CTCL mostly develops from CD4 T cells with the skin-tropic memory phenotype. Malignant T cells in MF lesions show the phenotype of skin resident memory T cells (T_RM), which reside in the peripheral tissues for long periods and do not recirculate. On the other hand, malignant T cells in SS represent the phenotype of central memory T cells (T_CM), which are characterized by recirculation to and from the blood and lymphoid tissues. The kinetics and the functional characteristics of malignant cells in CTCL are still unclear due, in part, to the fact that both the malignant cells and the T cells exerting anti-tumor activity possess the same characteristics as T cells. Capturing the features of both the malignant and the benign T cells is necessary for understanding the pathogenesis of CTCL and would lead to new therapeutic strategies specifically targeting the skin malignant T cells or benign T cells.