"Next top" mouse models advancing CTCL research

This review systematically describes the application of in vivo mouse models in studying cutaneous T-cell lymphoma (CTCL), a complex hematological neoplasm. It highlights the diverse research approaches essential for understanding CTCL's intricate pathogenesis and evaluating potential treatments. The review categorizes various mouse models, including xenograft, syngeneic transplantation, and genetically engineered mouse models (GEMMs), emphasizing their contributions to understanding tumor-host interactions, gene functions, and studies on drug efficacy in CTCL. It acknowledges the limitations of these models, particularly in fully replicating human immune responses and early stages of CTCL. The review also highlights novel developments focusing on the potential of skin-targeted GEMMs in studying natural skin lymphoma progression and interactions with the immune system from onset. In conclusion, a balanced understanding of these models' strengths and weaknesses are essential for accelerating the deciphering of CTCL pathogenesis and developing treatment methods. The GEMMs engineered to target specifically skin-homing CD4+ T cells can be the next top mouse models that pave the way for exploring the effects of CTCL-related genes.

Paediatric onset lymphomatoid papulosis: results of a multicentre retrospective cohort study, on behalf of the EORTC Cutaneous Lymphoma Tumours Group (CLTG)

BACKGROUND

Lymphomatoid Papulosis (LyP) is a rare cutaneous T-cell lymphoproliferative disorder. Comprehensive data on LyP in the paediatric population is scarce.

OBJECTIVES

To characterize epidemiological, clinical, histopathological, and prognostic features of paediatric LyP.

METHODS

This was a retrospective, multicentre international cohort study including 87 cases of children and adolescents with LyP diagnosed between 1998 and 2022. Patients aged ≤ 18 years old at disease onset were included. Diagnosis was made in each centre based on clinical-pathological correlation.

RESULTS

Eighty-seven patients from 12 centres were included. The mean age at onset was 7.0 years (range 3 months-18 years) with a male to female ratio of 2:1. The mean time between onset of first cutaneous lesions and diagnosis was 1.3 years (range 0-14 years). Initial misdiagnosis concerned 26.4% of patients. Initially, LyP was most often misdiagnosed as Pityriasis lichenoides et varioliformis acuta (PLEVA), insect bites, or mollusca contagiosa. Erythematous papules or papulonodules were the most frequent clinical presentation. Pruritus was specifically mentioned for 20.7% of patients. The main histological subtype was type A in 55.1% of the cases. If analysed, monoclonal TCR rearrangement was found in 76.5% of the skin biopsies. The overall survival rate was 100% with follow up at 5 years available for 33 patients and at 15 years for 8 patients. A development of associated haematological malignancy (HM) occurred in 9.6% of the cases (7/73), including four mycosis fungoides (MF) cases, one primary cutaneous anaplastic large cell lymphoma (pc-ALCL), one systemic ALCL and one case of acute myeloid leukaemia. If we compare incidence rates of cancer with the world 0-19 years old population from 2001-2010, we estimate a significantly higher risk of associated malignancy in general, occurring before the age of 19 years old with incidence rate ratio of 87.49 (CI 86.01-88.99).

CONCLUSIONS

We report epidemiological data from a large international cohort of children and adolescents with LyP. Overall the prognosis of the disease is good, with excellent survival rates for all patients. Due to increased risk of associated HM, a long-term follow-up should be recommended for LyP patients.

Reassessing human MHC-I genetic diversity in T cell studies

The Major Histocompatibility Complex class I (MHC-I) system plays a vital role in immune responses by presenting antigens to T cells. Allele specific technologies, including recombinant MHC-I technologies, have been extensively used in T cell analyses for COVID-19 patients and are currently used in the development of immunotherapies for cancer. However, the immense diversity of MHC-I alleles presents challenges. The genetic diversity serves as the foundation of personalized medicine, yet it also poses a potential risk of exacerbating healthcare disparities based on MHC-I alleles. To assess potential biases, we analysed (pre)clinical publications focusing on COVID-19 studies and T cell receptor (TCR)-based clinical trials. Our findings reveal an underrepresentation of MHC-I alleles associated with Asian, Australian, and African descent. Ensuring diverse representation is vital for advancing personalized medicine and global healthcare equity, transcending genetic diversity. Addressing this disparity is essential to unlock the full potential of T cells for enhancing diagnosis and treatment across all individuals.

Evaluation of Quality of Life and Treatment Satisfaction in Newly Diagnosed Cutaneous T-Cell Lymphoma Patients

BACKGROUND

Little is known about the impact of MF on quality of life (QoL) in newly diagnosed patients.

OBJECTIVES

To describe the impact of the MF diagnosis on QoL, patient expectations, and treatment satisfaction over the first 6 months after diagnosis.

METHODS

Outcomes of this prospective cohort study of newly diagnosed MF patients conducted between 2020 and 2022 at the Leiden University Medical Center included the Skindex-29, RAND-12 Health Survey, degree of itch, pain, and fatigue (Visual Analogue Scale (VAS)), patient expectations, and Client Satisfaction Questionnaire-8 (CSQ-8), measured at baseline and after six months.

RESULTS

A total of 28 patients with MF were included. At baseline, 66% (n = 18) "strongly-totally" expected positive effects of the treatment. At the time of diagnosis, 28% of the patients (n = 8) were moderately to severely affected. There was no statistical change in the Skindex-29 score sum score (20 [10-34] vs. 20 [9-36]; p = 0.81) or in the other three subdomains, the RAND-12 scores, and the VAS itch, pain, and fatigue over time. Treatment satisfaction was high overall.

CONCLUSION

Despite that the newly diagnosed MF patients anticipate a positive treatment effect, few improvements in QoL and symptom reduction were found. These data can be used for adequate expectation management and provide a rationale for further evaluation of treatment regimens in these patients.

The development of in vitro organotypic 3D vulvar models to study tumor-stroma interaction and drug efficacy

BACKGROUND

Vulvar squamous cell carcinoma (VSCC) is a rare disease with a poor prognosis. To date, there's no proper in vitro modeling system for VSCC to study its pathogenesis or for drug evaluation.

METHODS

We established healthy vulvar (HV)- and VSCC-like 3D full thickness models (FTMs) to observe the tumor-stroma interaction and their applicability for chemotherapeutic efficacy examination. VSCC-FTMs were developed by seeding VSCC tumor cell lines (A431 and HTB117) onto dermal matrices harboring two NF subtypes namely papillary fibroblasts (PFs) and reticular fibroblasts (RFs), or cancer-associated fibroblasts (CAFs) while HV-FTMs were constructed with primary keratinocytes and fibroblasts isolated from HV tissues.

RESULTS

HV-FTMs highly resembled HV tissues in terms of epidermal morphogenesis, basement membrane formation and collagen deposition. When the dermal compartment shifted from PFs to RFs or CAFs in VSCC-FTMs, tumor cells demonstrated more proliferation, EMT induction and stemness. In contrast to PFs, RFs started to lose their phenotype and express robust CAF-markers α-SMA and COL11A1 under tumor cell signaling induction, indicating a favored 'RF-to-CAF' transition in VSCC tumor microenvironment (TME). Additionally, chemotherapeutic treatment with carboplatin and paclitaxel resulted in a significant reduction in tumor-load and invasion in VSCC-FTMs.

CONCLUSION

We successfully developed in vitro 3D vulvar models mimicking both healthy and tumorous conditions which serve as a promising tool for vulvar drug screening programs. Moreover, healthy fibroblasts demonstrate heterogeneity in terms of CAF-activation in VSCC TME which brings insights in the future development of novel CAF-based therapeutic strategies in VSCC.

Autoantibody subclass predominance is not driven by aberrant class switching or impaired B cell development

A subset of autoimmune diseases is characterized by predominant pathogenic IgG4 autoantibodies (IgG4-AID). Why IgG4 predominates in these disorders is unknown. We hypothesized that dysregulated B cell maturation or aberrant class switching causes overrepresentation of IgG4+ B cells and plasma cells. Therefore, we compared the B cell compartment of patients from four different IgG4-AID with two IgG1-3-AID and healthy donors, using flow cytometry. Relative subset abundance at all maturation stages was normal, except for a, possibly treatment-related, reduction in immature and naïve CD5+ cells. IgG4+ B cell and plasma cell numbers were normal in IgG4-AID patients, however they had a (sub)class-independent 8-fold increase in circulating CD20-CD138+ cells. No autoreactivity was found in this subset. These results argue against aberrant B cell development and rather suggest the autoantibody subclass predominance to be antigen-driven. The similarities between IgG4-AID suggest that, despite displaying variable clinical phenotypes, they share a similar underlying immune profile.

Unveiling the hidden struggles: Exploring the profound impact of advanced stage cutaneous T-cell lymphoma on quality of life

Erythrodermic mycosis fungoides and Sézary syndrome are chronic, relapsing-remitting diseases that greatly impacts patients' quality of life (QoL). Mogamulizumab-kpkc (Mogamulizumab) is a novel therapeutic agent for cutaneous T-cell lymphomas with a notable impact on progression-free survival. Qualitative assessment methods allow a broader exploration and greater insight in individual patient experience than quantitative studies. However, there is limited data on the impact of mogamulizumab on health-related QoL. To investigate the impact of erythrodermic cutaneous T-cell lymphoma (E-CTCL) on QoL and the effect of mogamulizumab on the QoL. Semi-structured interview were conducted with seven patients with E-CTCL that were receiving mogamulizumab treatment. Five major themes arose: Diagnosis and the diagnostic delay and uncertainty experienced by participants; Physical functioning due to the high symptom burden; Psychological and social functioning considering the significant impact on daily life; Treatment and the effect of mogamulizumab; and Support by family, friends and health professionals. Mogamulizumab therapy resulted in a significant decrease of symptoms. The small sample size should also be taken into account although data saturation was reached. This study gives a broad insight into the large impact of E-CTCL and the major consequences on the physical functioning as well as on the emotional/psychological and social well-being. Mogamulizumab appears to have a positive effect on symptoms.

EORTC consensus recommendations for the treatment of mycosis fungoides/Sézary syndrome - Update 2023

On behalf of the EORTC Cutaneous Lymphoma Tumours Group (EORTC-CLTG) and following up on earlier versions published in 2006 and 2017 this document provides an updated standard for the treatment of mycosis fungoides and Sézary syndrome (MF/SS). It considers recent relevant publications and treatment options introduced into clinical practice after 2017. Consensus was established among the authors through a series of consecutive consultations in writing and a round of discussion. Treatment options are assigned to each disease stage and, whenever possible and clinically useful, separated into first- and second line options annotated with levels of evidence. Major changes to the previous version include the incorporation of chlormethine, brentuximab vedotin, and mogamulizumab, recommendations on the use of pegylated interferon α (after withdrawal of recombinant unpegylated interferons), and the addition of paragraphs on supportive therapy and on the care of older patients. Still, skin-directed therapies are the most appropriate option for early-stage MF and most patients have a normal life expectancy but may suffer morbidity and impaired quality of life. In advanced disease treatment options have expanded recently. Most patients receive multiple consecutive therapies with treatments often having a relatively short duration of response. For those patients prognosis is still poor and only for a highly selected subset long term remission can be achieved with allogeneic stem cell transplantation. Understanding of the disease, its epidemiology and clinical course, and its most appropriate management are gradually advancing, and there is well-founded hope that this will lead to further improvements in the care of patients with MF/SS.

Use of Pegylated Interferon Alpha-2a in Cutaneous T-cell Lymphoma: A Retrospective Case Collection

Mycosis fungoides and Sézary syndrome are rare and largely incurable types of cutaneous T-cell lymphoma with limited therapeutic options. In 1984 Bunn et al. reported that interferon alpha is an efficient monotherapy in cutaneous T-cell lymphoma and 14 years later it was shown in a prospective, randomized trial that a combination of interferon alpha and psoralen plus ultraviolet A therapy (PUVA) is most efficient in the treatment of cutaneous T-cell lymphoma. Since then interferon alpha as single agent or, most often, in combination with phototherapy and/or retinoids has been integrated as standard of care in cutaneous T-cell lymphoma guidelines worldwide. However, production of interferon alpha was discontinued recently worldwide and pegylated interferon alpha-2a (PEG-IFNα) has been used as an alternative therapy. In contrast to numerous interferon alpha studies, only a few studies focusing on PEG-IFNα are available. Therefore, the aim of this study was to conduct a retrospective data collection to report on the efficacy, adverse events and therapy regimens of PEG-IFNα in cutaneous T-cell lymphoma. In 28 patients with cutaneous T-cell lymphoma treated in Germany and in the Netherlands, 36% of patients achieved complete remission, 36% partial remission and 29% stable disease. Eighteen percent of patients developed adverse events during therapy, which led to the discontinuation of PEG-IFNα therapy in 2 patients. The most common concomittant therapies were oral PUVA phototherapy and local radiotherapy. In conclusion, PEG-IFNα, especially in combination with skin-directed therapies, is an effective treatment option for cutaneous T-cell lymphoma in clinical practice.

Socs1-knockout in skin-resident CD4+ T cells in a protracted contact-allergic reaction results in an autonomous skin inflammation with features of early-stage mycosis fungoides

Recent detailed genomic analysis of mycosis fungoides (MF) identified suppressor of cytokine signaling 1 (SOCS1), an inhibitor of JAK/STAT signaling, as one of the frequently deleted tumor suppressors in MF, and one-copy deletion of SOCS1 was confirmed in early-stage MF lesions. To better understand the functional role of SOCS1 in the genesis of MF, we used a genetically engineered mouse model emulating heterozygous SOCS1 loss in skin resident CD4+ T cells. In these mice an experimentally induced contact-allergic reaction was maintained for 20 weeks. Ten weeks after discontinuing contact-allergic challenges, only the skin with locally one-copy deletion of Socs1 in CD4+ T cells still showed high numbers of CD3+/CD4+ Socs1 k.o. cells in the dermis (p ＜ 0.0001) with prevalent Stat3 activation (p ＜0.001). And in one out of 9 mice, this had progressed to far more dramatic increases, including the thickened epidermis, and with an explosive growth of Socs1 k.o. T cells in circulation; indicative of cutaneous lymphoma. Hence, we show that Socs1 mono-allelic loss in CD4+ T cells locally in protractedly inflamed skin results in autonomous skin inflammation with features of early-stage MF.

Artificial intelligence in digital pathology of cutaneous lymphomas: a review of the current state and future perspectives

Primary cutaneous lymphomas (CLs) represent a heterogeneous group of T-cell lymphomas and B-cell lymphomas that present in the skin without evidence of extracutaneous involvement at time of diagnosis. CLs are largely distinct from their systemic counterparts in clinical presentation, histopathology, and biological behavior and, therefore, require different therapeutic management. Additional diagnostic burden is added by the fact that several benign inflammatory dermatoses mimic CL subtypes, requiring clinicopathological correlation for definitive diagnosis. Due to the heterogeneity and rarity of CL, adjunct diagnostic tools are welcomed, especially by pathologists without expertise in this field or with limited access to a centralized specialist panel. The transition into digital pathology workflows enables artificial intelligence (AI)-based analysis of patients' whole-slide pathology images (WSIs). AI can be used to automate manual processes in histopathology but, more importantly, can be applied to complex diagnostic tasks, especially suitable for rare disease like CL. To date, AI-based applications for CL have been minimally explored in literature. However, in other skin cancers and systemic lymphomas, disciplines that are recognized here as the building blocks for CLs, several studies demonstrated promising results using AI for disease diagnosis and subclassification, cancer detection, specimen triaging, and outcome prediction. Additionally, AI allows discovery of novel biomarkers or may help to quantify established biomarkers. This review summarizes and blends applications of AI in pathology of skin cancer and lymphoma and proposes how these findings can be applied to diagnostics of CL.

Identifying unmet needs and challenges in the definition of a plaque in mycosis fungoides: An EORTC-CLTG/ISCL survey

BACKGROUND

Consensus about the definition and classification of 'plaque' in mycosis fungoides is lacking.

OBJECTIVES

To delineate a comprehensive view on how the 'plaque' entity is defined and managed in clinical practice; to evaluate whether the current positioning of plaques in the TNMB classification is adequate.

METHODS

A 12-item survey was circulated within a selected panel of 22 experts (pathologists, dermatologists, haematologists and oncologists), members of the EORTC and International Society for Cutaneous Lymphoma. The questionnaire discussed clinical and histopathological definitions of plaques and its relationship with staging and treatment.

RESULTS

Total consensus and very high agreement rates were reached in 33.3% of questions, as all panellists regularly check for the presence of plaques, agree to evaluate the presence of plaques as a potential separate T class, and concur on the important distinction between plaque and patch for the management of early-stage MF. High agreement was reached in 41.7% of questions, since more than 50% of the responders use Olsen's definition of plaque, recommend the distinction between thin/thick plaques, and agree on performing a biopsy on the most infiltrated/indurated lesion. High divergence rates (25%) were reported regarding the possibility of a clinically based distinction between thin and thick plaques and the role of histopathology to plaque definition.

CONCLUSIONS

The definition of 'plaque' is commonly perceived as a clinical entity and its integration with histopathological features is generally reserved to specific cases. To date, no consensus is achieved as for the exact definition of thin and thick plaques and current positioning of plaques within the TNMB system is considered clinically inadequate. Prospective studies evaluating the role of histopathological parameters and other biomarkers, as well as promising diagnostic tools, such as US/RM imaging and high-throughput blood sequencing, are much needed to fully integrate current clinical definitions with more objective parameters.

HLA expression as a risk factor for metastases of cutaneous squamous-cell carcinoma in organ- transplant recipients

BACKGROUND

Solid organ-transplant recipients (SOTR) have an increased risk of cutaneous squamous-cell carcinoma (cSCC), metastasis and death from cSCC. In immunocompetent patients with mucosal SCC, downregulation of HLA class I is associated with poor prognosis. Since the degree of HLA expression on tumor cells could play a role in immunogenicity and pathophysiology of cSCC metastasis, we hypothesized that decreased HLA expression is associated with an increased risk of metastasis.

METHODS

We compared HLA expression between primary metastasized cSCCs, their metastases, and non-metastasized cSCCs from the same patients. Samples were stained for HLA-A, HLA-B/-C and quantified by calculating the difference in immunoreactivity score (IRS) of the primary cSCC compared with all non-metastasized cSCCs.

RESULTS

The mean IRS score for HLA-B/C expression was 2.07 point higher in metastasized compared to non-metastasized cSCCs (p = 0.065, 95 % CI -0.18-4.32). 83.3 % of the primary metastasized cSCCs had an IRS score of 4 or higher, compared to 42.9 % in non-metastasized cSCCs. Moderately to poorly differentiated cSCCs had more HLA class I expression compared to well-differentiated cSCCs.

CONCLUSION

Contrary to immunocompetent patients, HLA-B/C expression tends to be upregulated in metastasized cSCC compared to non-metastasized cSCC in SOTR, suggesting that different tumor escape mechanisms play a role in SOTR compared to immunocompetent patients.

Itch in patients with cutaneous T-cell lymphoma as a quality of life indicator

Background

Cutaneous T-cell lymphoma (CTCL) is a chronic and progressive disease that has a major impact on quality of life (QoL).

Objectives

To describe the impact of the different stages of disease in patients with classical mycosis fungoides, folliculotropic mycosis fungoides, and Sézary syndrome on generic- and dermatology-specific QoL and the relation with itch.

Methods

A cross-sectional cohort study of patients with classical mycosis fungoides, folliculotropic mycosis fungoides, and Sézary syndrome was performed. Outcomes were the Skindex-29 score, Impact of Chronic Skin Disease on Daily Life which includes a visual analogue scale itch, and RAND-12.

Results

One hundred six patients with CTCL were included. Compared to the total mycosis fungoides group, patients with Sézary syndrome had significantly worse Skindex-29 scores. Patients with advanced disease had statistically higher scores for the symptom (P = .007), functioning (P = .002), and total score (P = .012). The degree of itching was strongly correlated with the total Skindex-29 score (R = 0.713, P < .001).

Conclusion

The different stages of CTCL can have a significant effect on multiple domains of generic- and dermatology-specific QoL. Itch was strongly correlated with QoL and therefore can be used as an overall QoL indicator. The effect on QoL, even in patients with early-stage disease, should not be underestimated.

In vivo modelling of cutaneous T-cell lymphoma: The role of SOCS1

Introduction

Mycosis fungoides (MF), the most common type of Cutaneous T cell Lymphoma (CTCL), is characterized by an inflamed skin intermixed with proliferating malignant mature skin-homing CD4+ T cells. Detailed genomic analyses of MF skin biopsies revealed several candidate genes possibly involved in genesis of these tumors and/or potential targets for therapy. These studies showed, in addition to common loss of cell cycle regulator CDKN2A, activation of several oncogenic pathways, most prominently and consistently involving JAK/STAT signaling. SOCS1, an endogenous inhibitor of the JAK/STAT signaling pathway, was identified as a recurrently deleted gene in MF, already occurring in the earliest stages of the disease.

Methods

To explore the mechanisms of MF, we create in vivo mouse models of autochthonous CTCLs and these genetically engineered mouse models (GEMMS) can also serve as valid experimental models for targeted therapy. We describe the impact of allelic deletion of Socs1 in CD4 T cells of the skin. To achieve this, we crossed inducible Cre-transgenic mice in the CD4 lineage with transgenic mice carrying floxed genes of Socs1. We first determined optimal conditions for Socs1 ablation with limited effects on circulating CD4 T-cells in blood. Next, we started time-course experiments mimicking sustained inflammation, typical in CTCL. FACS analysis of the blood was done every week. Skin biopsies were analyzed by immunocytochemical staining at the end of the experiment.

Results

We found that the Socs1 knockout transgenic group had thicker epidermis of treated skin compared with the control group and had more CD3 and CD4 in the skin of the transgenic group compared to the control group. We also noted more activation of Stat3 by staining for P-Stat3 in Socs1 knockout compared to wt CD4+T cells in the skin. The results also indicated that single copy loss of Socs1 in combination with sustained inflammation is insufficient to start a phenotype resembling early stage mycosis fungoides within eight weeks in these mice.

Conclusion

In sum, we developed and optimized an autochthonous murine model permitting selective knockout of Socs1 in skin infiltrating CD4 T-cells. This paves the way for more elaborate experiments to gain insight in the oncogenesis of CTCL.

DOT1L inhibition does not modify the sensitivity of cutaneous T cell lymphoma to pan-HDAC inhibitors in vitro

Cutaneous T-cell lymphomas (CTCLs) are a subset of T-cell malignancies presenting in the skin. The treatment options for CTCL, in particular in advanced stages, are limited. One of the emerging therapies for CTCL is treatment with histone deacetylase (HDAC) inhibitors. We recently discovered an evolutionarily conserved crosstalk between HDAC1, one of the targets of HDAC inhibitors, and the histone methyltransferase DOT1L. HDAC1 negatively regulates DOT1L activity in yeast, mouse thymocytes, and mouse thymic lymphoma. Here we studied the functional relationship between HDAC inhibitors and DOT1L in two human CTCL cell lines, specifically addressing the question whether the crosstalk between DOT1L and HDAC1 observed in mouse T cells plays a role in the therapeutic effect of clinically relevant broad-acting HDAC inhibitors in the treatment of human CTCL. We confirmed that human CTCL cell lines were sensitive to treatment with pan-HDAC inhibitors. In contrast, the cell lines were not sensitive to DOT1L inhibitors. Combining both types of inhibitors did neither enhance nor suppress the inhibitory effect of HDAC inhibitors on CTCL cells. Thus our in vitro studies suggest that the effect of commonly used pan-HDAC inhibitors in CTCL cells relies on downstream effects other than DOT1L misregulation.

Topical Bimiralisib Shows Meaningful Cutaneous Drug Levels in Healthy Volunteers and Mycosis Fungoides Patients but No Clinical Activity in a First-in-Human, Randomized Controlled Trial

Mycosis fungoides (MF) is a subtype of CTCL with a low incidence and high medical need for novel treatments. The objective of this randomized, placebo-controlled, double-blinded, first-in-human study was to evaluate safety, efficacy, cutaneous and systemic pharmacokinetics (PK) of topical bimiralisib in healthy volunteers (HVs) and MF patients. In this trial, a total of 6 HVs and 19 early-stage MF patients were treated with 2.0% bimiralisib gel and/or placebo. Drug efficacy was assessed by the Composite Assessment of Index Lesion Severity (CAILS) score, supported by objective measuring methods to quantify lesion severity. PK blood samples were collected frequently and cutaneous PK was investigated in skin punch biopsies on the last day of treatment. Local distribution of bimiralisib in HVs showed a mean exposure of 2.54 µg/g in the epidermis. A systemic concentration was observed after application of a target dose of 2 mg/cm² on 400 cm², with a mean C_avg of 0.96 ng/mL. Systemic exposure of bimiralisib was reached in all treated MF patients, and normalized plasma concentrations showed a 144% increased exposure compared to HVs, with an observed mean C_avg of 4.49 ng/mL and a mean cutaneous concentration of 5.3 µg/g. No difference in CAILS or objective lesion severity quantification upon 42 days of once-daily treatment was observed in the MF patient group. In general, the treatment was well tolerated in terms of local reactions as well as systemic adverse events. In conclusion, we showed that topical bimiralisib treatment leads to (i) meaningful cutaneous drug levels and (ii) well-tolerated systemic drug exposure in MF patients and (iii) a lack of clinical efficacy, in need of further exploration due to numerous unknown factors, before depreciation of topical bimiralisib as a novel therapeutic drug for CTCLs.

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.

Dermatologic Events Associated with the Anti-CCR4 Antibody Mogamulizumab: Characterization and Management

The CCR4-directed monoclonal antibody mogamulizumab has been shown to significantly improve progression-free survival and overall response rate compared with vorinostat in adults with relapsed/refractory mycosis fungoides (MF) and Sézary syndrome (SS). One of the most common adverse events seen with mogamulizumab in MF/SS patients is rash. Because of the protean nature of MF/SS and the variable clinical and histopathological features of mogamulizumab-associated rash, healthcare providers may have difficulty distinguishing rash from disease, and may not be aware of appropriate treatment strategies for this generally manageable adverse event. The objective of this report was to combine results from published literature with experiences and recommendations from multiple investigators and institutions into clinical best practice recommendations to assist healthcare providers in identifying and managing mogamulizumab-associated rash. Optimal management, which includes biopsy confirmation and steroid treatment, requires a multidisciplinary approach among oncology, dermatology, and pathology practitioners.

Whole-genome profiling of primary cutaneous anaplastic large cell lymphoma

Primary cutaneous anaplastic large cell lymphoma (pcALCL), a hematological neoplasm caused by skin-homing CD30⁺ malignant T cells, is part of the spectrum of primary cutaneous CD30⁺ lymphoproliferative disorders. To date, only a small number of molecular alterations have been described in pcALCL and, so far, no clear unifying theme that could explain the pathogenetic origin of the disease has emerged among patients. In order to clarify the pathogenetic basis of pcALCL, we performed high-resolution genetic profiling (genome/transcriptome) of this lymphoma (n=12) by using whole-genome sequencing, whole-exome sequencing and RNA sequencing. Our study, which uncovered novel genomic rearrangements, copy number alterations and small-scale mutations underlying this malignancy, revealed that the cell cycle, T-cell physiology regulation, transcription and signaling via the PI-3-K, MAPK and G-protein pathways are cellular processes commonly impacted by molecular alterations in patients with pcALCL. Recurrent events affecting cancer-associated genes included deletion of PRDM1 and TNFRSF14, gain of EZH2 and TNFRSF8, small-scale mutations in LRP1B, PDPK1 and PIK3R1 and rearrangements involving GPS2, LINC-PINT and TNK1. Consistent with the genomic data, transcriptome analysis uncovered upregulation of signal transduction routes associated with the PI-3-K, MAPK and G-protein pathways (e.g., ERK, phospholipase C, AKT). Our molecular findings suggest that inhibition of proliferation-promoting pathways altered in pcALCL (particularly PI-3-K/AKT signaling) should be explored as potential alternative therapy for patients with this lymphoma, especially, for cases that do not respond to first-line skin-directed therapies or with extracutaneous disease.

Whole-genome profiling of primary cutaneous anaplastic large cell lymphoma

Primary cutaneous anaplastic large cell lymphoma (pcALCL), a hematological neoplasm caused by skin-homing CD30+ malignant T cells, is part of the spectrum of primary cutaneous CD30+ lymphoproliferative disorders. To date, only a small number of molecular alterations have been described in pcALCL, and so far, no clear unifying theme that could explain the pathogenetic origin of the disease has emerged among patients. To clarify the pathogenetic basis of pcALCL, we performed a high-resolution genetic profiling (genome/transcriptome) of this lymphoma (n=12) by using whole-genome sequencing, whole-exome sequencing and RNA sequencing. Our study, which uncovered novel genomic rearrangements, copy number alterations and small-scale mutations underlying this malignancy, revealed that the cell cycle, T-cell physiology regulation, transcription and signaling via the PI-3-K, MAPK and G-protein pathways are cellular processes commonly impacted by molecular alterations in patients with pcALCL. Recurrent events affecting cancer-associated genes included deletion of PRDM1 and TNFRSF14, gain of EZH2 and TNFRSF8, small-scale mutations in LRP1B, PDPK1 and PIK3R1 and rearrangements involving GPS2, LINC-PINT and TNK1. Consistent with the genomic data, transcriptome analysis uncovered upregulation of signal transduction routes associated with the PI-3-K, MAPK and G-protein pathways (e.g. ERK, phospholipase C, AKT). Our molecular findings suggest that inhibition of proliferation-promoting pathways altered in pcALCL (particularly PI-3-K/AKT signaling) should be explored as potential alternative therapy for patients with this lymphoma, especially, for cases that do not respond to first line skin-directed therapies or with extracutaneous disease.

Quality of life in patients with Mycosis Fungoides and Sézary Syndrome: a systematic review of the literature

Cutaneous T‐cell Lymphoma’s (CTCL) are a rare, heterogeneous group of T‐cell lymphomas that primarily manifest in the skin. Mycosis fungoides (MF) and Sézary syndrome (SS) are considered the classic types of CTCL. The diverse manifestation of CTCL results in a wide range of symptoms with a possible mild to severe impact on Quality of Life (QoL) depending on the disease stage. Previous studies on QoL in CTCL patients report diverse patient populations and use many different QoL instruments. In the current literature, a clear overview on the influence of the different stages of disease (early MF, late‐stage MF/SS or total group) on the QoL is lacking. Therefore, a systematic search of the literature was conducted using the PubMed, Embase, PsycINFO and Web of Science databases. Studies were included if they described QoL in patients with MF and SS retrieved by standardized instruments or qualitative interviews. In total, 24 studies were included using 18 different questionnaires to report on dermatology‐specific, cancer‐specific and generic QoL. The effect on QoL was found to be greater in patients with late‐stage disease as compared to early stage disease, with significant impairments on functional, emotional and physical domains. Nonetheless, even in patients with limited disease, QoL was mildly to moderately affected. Overall, pruritus was the most frequent reported and most bothersome symptom. Significant influence of the disease on daily life activities were found, not only in patients but also on caregivers and family. This broad, structured overview on QoL in MF and SS patients underlines the influence of disease stage on QoL, and therefore, recommends future studies to distinguish between disease stages when reporting results. Furthermore, this overview can inform clinicians in clinical practice by creating awareness of QoL deficits according to disease stage.

Deregulation of JAK2 signaling underlies primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma

Primary cutaneous CD8⁺ aggressive epidermotropic cytotoxic T-cell lymphoma (pcAECyTCL) is a rare variant of cutaneous T-cell lymphoma with an aggressive clinical course and a very poor prognosis. Until now, neither a systematic characterization of genetic alterations driving pcAECyTCL has been performed, nor effective therapeutic regimes for patients have been defined. Here, we present the first highresolution genetic characterization of pcAECyTCL by using wholegenome and RNA sequencing. Our study provides a comprehensive description of genetic alterations (i.e., genomic rearrangements, copy number alterations and small-scale mutations) with pathogenic relevance in this lymphoma, including events that recurrently impact genes with important roles in the cell cycle, chromatin regulation and the JAKSTAT pathway. In particular, we show that mutually exclusive structural alterations involving JAK2 and SH2B3 predominantly underlie pcAECyTCL. In line with the genomic data, transcriptome analysis uncovered upregulation of the cell cycle, JAK2 signaling, NF-κB signaling and a high inflammatory response in this cancer. Functional studies confirmed oncogenicity of JAK2 fusions identified in pcAECyTCL and their sensitivity to JAK inhibitor treatment. Our findings strongly suggest that overactive JAK2 signaling is a central driver of pcAECyTCL, and consequently, patients with this neoplasm would likely benefit from therapy with JAK2 inhibitors such as Food and Drug Adminstration-approved ruxolitinib.

The importance of assessing blood tumour burden in cutaneous T-cell lymphoma

Mycosis fungoides (MF) and Sézary syndrome (SS) are the best-studied subtypes of cutaneous T-cell lymphoma. The level of blood tumour burden in patients is important for diagnosis, disease staging, prognosis and management, as well as assessing treatment response. Until recently, the assessment of blood involvement was made using manual counts of morphologically atypical T cells (Sézary cells), but this approach may be subjective, and is affected by interobserver variability. Objective and consistent approaches to accurately quantifying blood involvement are required to ensure appropriate stage-related management of patients and to improve our understanding of the prognostic implications of blood tumour burden in these diseases. While assessment of blood involvement is common in SS and advanced-stage MF, an improved understanding of the implications of blood involvement at early disease stages could help identify patients more likely to progress to late-stage disease, and hence guide treatment decisions and frequency of follow-up assessment, ultimately improving patient outcomes. This concise review discusses the development of flow cytometry-based classifications for assessing blood involvement in MF and SS, and summarizes current recommendations for blood classification and assessment of blood response to treatment.

Primary cutaneous peripheral T-cell lymphoma, not otherwise specified: results of a multicentre European Organization for Research and Treatment of Cancer (EORTC) cutaneous lymphoma taskforce study on the clinico-pathological and prognostic features

BACKGROUND

Cutaneous peripheral T-cell lymphoma, not otherwise specified (PTL NOS) is an aggressive, but poorly characterized neoplasm.

OBJECTIVES

The European Organization for Research and Treatment of Cancer cutaneous lymphoma taskforce (EORTC CLTF) investigated 33 biopsies of 30 patients with primary cutaneous PTL NOS to analyse their clinical, histological, immunophenotypic features and outcome.

METHODS

Retrospective analysis of clinical data and histopathological features by an expert panel.

RESULTS

Cutaneous PTL NOS manifested clinically either with solitary or disseminated rapidly grown ulcerated tumours or disseminated papulo-nodular lesions. Histologically, a mostly diffuse or nodular infiltrate in the dermis and often extending into the subcutis was found. Epidermotropism was rarely present and only mild and focal. Unusual phenotypes were frequent, e.g. CD3⁺ /CD4^- /CD8^- and CD3⁺ /CD4⁺ /CD8⁺ . Moreover, 18% of the cases exhibited an aberrant expression of the B-cell marker CD20 by the tumour cells. All solitary tumours were located on the limbs and presented a high expression of GATA-3 but this did not correlate with outcome and therefore could not serve as a prognostic factor. The prognosis was shown to be generally poor with 10 of 30 patients (33%) dying of lymphoma within the follow-up of 36 months (mean value; range 3-144). The survival rates were 61% after 3 years (CI, 43-85%) and 54% after 5 years (CI, 36-81%). Small to medium-sized morphology of tumour cells was associated with a better outcome than medium to large or large tumour cells. Age, gender, clinical stage, CD4/CD8 phenotype and GATA-3 expression were not associated with prognosis. Chemotherapy was the most common treatment modality, but surgical excision and/or radiotherapy may represent an appropriate first-line treatment for solitary lesions.

CONCLUSIONS

Cutaneous PTL NOS shows an aggressive course in most patients independent of initial presentation, age and phenotype. Cytomorphology was identified as a prognostic factor. The data indicate a need for more effective treatment modalities in PTL NOS.

Cucurbitacin E and I target the JAK/STAT pathway and induce apoptosis in Sézary cells

Cutaneous T-cell lymphomas and leukemias (CTCLs) are a heterogeneous group of extranodal non-Hodgkin's lymphomas. These are characterized by an accumulation of malignant CD4⁺ T-lymphocytes in the skin, lymph nodes, and peripheral blood. Novel treatment options are needed for patients who progress to advanced stage disease. Cucurbitacin I has previously shown promising results in Sézary syndrome (Sz). A plethora of cucurbitacins, however, have not yet been tested in CTCL. Herein, we investigated the effect of cucurbitacin E and I in two CTCL cell lines. We show that both cucurbitacins decrease viability and cause apoptosis in these cell lines, although HuT-78 was more affected than SeAx (IC₅₀ of 17.38 versus 22.01 μM for cucurbitacin E and 13.36 versus 24.47 μM for cucurbitacin I). Moreover, both cucurbitacins decrease viability of primary cells of a Sz patient (56.46% for cucurbitacin E and 59.07% for cucurbitacin I). Furthermore, while JAK2 inhibition leads to decreased viability in SeAx cells (IC₅₀ of 9.98 and 29.15 μM for AZD1480 and ruxolitinib respectively), both JAK1 and JAK3 do not. This suggests that JAK2 has a preferential role in promoting survival. Western blotting in SeAx cells revealed that both cucurbitacins inhibit STAT3 activation (P < 0.0001), while only cucurbitacin I inhibits STAT5 activation (P = 0.05). This suggests that STAT3 plays a preferential role in the mechanism of action of these cucurbitacins. Nevertheless, a role of STAT5 and JAK2 cannot be excluded and should be explored further. This knowledge could contribute to the development of effective therapies for CTCL and other malignancies involving dysfunction of the JAK/STAT pathway.

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Cucurbitacin E and I decrease viability and cause apoptosis in Sézary cell lines

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Both cucurbitacins decrease viability of primary cells of a Sézary patient

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STAT3 appears to play a role in the mechanism of action of cucurbitacin E and I

Botulinum toxin type A in the treatment of Raynaud's phenomenon

Raynaud's phenomenon is a vasospastic disorder clinically characterized by cold or stress-induced discoloration of the skin, pain and ulcers of the fingers or toes. Although this phenomenon might be self-limiting, there is a subgroup of patients requiring a therapeutic approach. The majority of patients do well on conservative measures; however, there is also a subgroup requiring systemic treatment. The efficacy of these systemic treatments is currently not thoroughly investigated. Furthermore, no uniform guidelines exist regarding the choice for a treatment option. In the past several years, several reports have shown the benefits of botulinum toxin for the treatment of Raynaud's phenomenon. In this case series, we report our experience with botulinum toxin type A in the treatment of Raynaud's phenomenon.

Whole-genome analysis uncovers recurrent IKZF1 inactivation and aberrant cell adhesion in blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematological malignancy with a poorly understood pathobiology and no effective therapeutic options. Despite a few recurrent genetic defects (eg, single nucleotide changes, indels, large chromosomal aberrations) have been identified in BPDCN, none are disease‐specific, and more importantly, none explain its genesis or clinical behavior. In this study, we performed the first high resolution whole‐genome analysis of BPDCN with a special focus on structural genomic alterations by using whole‐genome sequencing and RNA sequencing. Our study, the first to characterize the landscape of genomic rearrangements and copy number alterations of BPDCN at nucleotide‐level resolution, revealed that IKZF1, a gene encoding a transcription factor required for the differentiation of plasmacytoid dendritic cell precursors, is focally inactivated through recurrent structural alterations in this neoplasm. In concordance with the genomic data, transcriptome analysis revealed that conserved IKZF1 target genes display a loss‐of‐IKZF1 expression pattern. Furthermore, up‐regulation of cellular processes responsible for cell‐cell and cell‐ECM interactions, which is a hallmark of IKZF1 deficiency, was prominent in BPDCN. Our findings suggest that IKZF1 inactivation plays a central role in the pathobiology of the disease, and consequently, therapeutic approaches directed at reestablishing the function of this gene might be beneficial for patients.

Plaque stage folliculotropic mycosis fungoides: histopathologic features and prognostic factors in a series of 40 patients

BACKGROUND

Folliculotropic mycosis fungoides (FMF) is a distinct variant of mycosis fungoides. Recent studies recognized indolent and aggressive subgroups of FMF, but there is controversy how patients presenting with plaques should be classified. The present study describes the histopathologic features of 40 FMF plaques. The aim of the study was to identify risk factors for disease progression and poor outcome in this group.

METHODS

Clinical, histopathological, and immunophenotypical data from 40 patients with plaque stage FMF were reviewed and analysed for risk factors for disease progression and survival.

RESULTS

After a median follow-up of 80 months, disease progression occurred in 20 of 40 patients. Percentage of atypical cells, cell size, percentage of Ki-67+ cells, and co-existent interfollicular epidermotropism, but not the extent of perifollicular infiltrates, were associated with disease progression and reduced survival, while extensive follicular mucinosis was associated with increased survival.

CONCLUSIONS

This study underlines that FMF patients presenting with plaques represent a heterogeneous group and that a subgroup of these patients may have an indolent clinical course. It further shows that histological examination is a valuable tool to differentiate between indolent and aggressive disease.

Frequency and prognosis of associated malignancies in 504 patients with lymphomatoid papulosis

Background

Lymphomatoid papulosis (LyP) can be associated with other haematological malignancies (HM), but reported percentages vary from 20% to over 50%.

Objective

To evaluate the frequency and prognostic significance of associated HM and non‐HM in LyP patients.

Methods

In this multicentre cohort study, the complete Dutch LyP population was included from the Dutch Cutaneous Lymphoma Registry between 1985 and 2018. Clinical and histopathological information was retrieved from every individual patient.

Results

After a median follow‐up of 120 months (range, 6–585), an associated HM was observed in 78/504 (15.5%) patients. Most common associated HM were mycosis fungoides (MF; n = 31) and anaplastic large‐cell lymphoma (ALCL; n = 29), while 19 patients had another HM of B‐cell (n = 14) or myeloid origin (n = 5). Even after a 25‐year follow‐up period, percentages of associated HM did not exceed 20%. Thirty‐nine of 465 patients (8.4%) without a prior or concurrent associated HM developed an associated HM during follow‐up, after a median of 68 months (range of 3–286 months). Nine of 78 patients died of associated HM, including 6/22 patients developing extracutaneous ALCL, while all patients with associated MF or skin‐limited ALCL had an excellent prognosis. Compared with the general population, LyP patients showed an increased risk (relative risk, 2.8; 95% confidence intervals, 2.4–3.3) for non‐HM, in particular cutaneous squamous cell carcinoma, melanoma and intestinal/lung/bladder cancer.

Conclusions

An associated HM was reported in 15.5% of the LyP patients, particularly MF and ALCL. Although the frequency of associated HM is lower than suggested and the prognosis of most patients with associated HM is excellent, a small subgroup will develop aggressive disease, in particular extracutaneous ALCL. Furthermore, LyP patients have a higher risk of developing other malignancies. Clinicians should be aware of these risks, and LyP patients require close monitoring.

Linked article: F. Rongioletti. J Eur Acad Dermatol Venereol 2020; 34: 216–217. https://doi.org/10.1111/jdv.16157.

Generalized Molluscum Contagiosum Successfully Treated with Interferon-Alpha in a Patient with Folliculotropic Mycosis Fungoides

We present the case of a 50-year-old patient with folliculotropic mycosis fungoides (FMF) unresponsive to retinoids and the chemotherapeutic regimens CHOP, gemcitabine, and brentuximab-vedotin. During immunosuppressive therapy, the patient developed extensive progressive molluscum contagiosum. The mollusca did not respond to topical imiquimod but showed a swift complete response to interferon-alpha 2a (IFNa). Recently, the patient started with alemtuzumab as induction therapy for an allogenic stem cell transplantation and simultaneously continued IFNa therapy.

Acquired N-Linked Glycosylation Motifs in B-Cell Receptors of Primary Cutaneous B-Cell Lymphoma and the Normal B-Cell Repertoire

Primary cutaneous follicle center lymphoma (PCFCL) is a rare mature B-cell lymphoma with an unknown etiology. PCFCL resembles follicular lymphoma (FL) by cytomorphologic and microarchitectural criteria. FL B cells are selected for N-linked glycosylation motifs in their B-cell receptors (BCRs) that are acquired during continuous somatic hypermutation. The stimulation of mannosylated BCR by lectins on the tumor microenvironment is therefore a candidate driver in FL pathogenesis. We investigated whether the same mechanism could play a role in PCFCL pathogenesis. Full-length functional variable, diversity, and joining gene sequences of 18 PCFCL and 8 primary cutaneous diffuse large B-cell lymphoma, leg-type were identified by unbiased Anchoring Reverse Transcription of Immunoglobulin Sequences and Amplification by Nested PCR and BCR reconstruction from RNA sequencing data. Low BCR variation demonstrated negligible ongoing somatic hypermutation in PCFCL and primary cutaneous diffuse large B-cell lymphoma, leg-type, and indicated that the PCFCL microarchitecture does not act as a functional germinal center. Similar to FL but in contrast to primary cutaneous diffuse large B-cell lymphoma, leg-type, BCR genes of 15 PCFCLs (83%) had acquired N-linked glycosylation motifs. These motifs were located at the BCR positions converted to N-linked glycosylation motifs in normal B-cell repertoires with low prevalence but mostly at different positions than those found in FL. The cutaneous localization of PCFCL might suggest a role for lectins from commensal skin bacteria in PCFCL lymphomagenesis.

Loss of the GPI-anchor in B-lymphoblastic leukemia by epigenetic downregulation of PIGH expression

Adult B-lymphoblastic leukemia (B-ALL) is a hematological malignancy characterized by genetic heterogeneity. Despite successful remission induction with classical chemotherapeutics and novel targeted agents, enduring remission is often hampered by disease relapse due to outgrowth of a pre-existing subclone resistant against the treatment. In this study, we show that small glycophosphatidylinositol (GPI)-anchor deficient CD52-negative B-cell populations are frequently present already at diagnosis in B-ALL patients, but not in patients suffering from other B-cell malignancies. We demonstrate that the GPI-anchor negative phenotype results from loss of mRNA expression of the PIGH gene, which is involved in the first step of GPI-anchor synthesis. Loss of PIGH mRNA expression within these B-ALL cells follows epigenetic silencing rather than gene mutation or deletion. The coinciding loss of CD52 membrane expression may contribute to the development of resistance to alemtuzumab (ALM) treatment in B-ALL patients resulting in the outgrowth of CD52-negative escape variants. Additional treatment with 5-aza-2'-deoxycytidine may restore expression of CD52 and revert ALM resistance.

Genomic analysis reveals recurrent deletion of JAK-STAT signaling inhibitors HNRNPK and SOCS1 in mycosis fungoides

Mycosis fungoides (MF) is the most common cutaneous T-cell lymphoma (CTCL). Causative genetic alterations in MF are unknown. The low recurrence of pathogenic small-scale mutations (ie, nucleotide substitutions, indels) in the disease, calls for the study of additional aspects of MF genetics. Here, we investigated structural genomic alterations in tumor-stage MF by integrating whole-genome sequencing and RNA-sequencing. Multiple genes with roles in cell physiology (n = 113) and metabolism (n = 92) were found to be impacted by genomic rearrangements, including 47 genes currently implicated in cancer. Fusion transcripts involving genes of interest such as DOT1L, KDM6A, LIFR, TP53, and TP63 were also observed. Additionally, we identified recurrent deletions of genes involved in cell cycle control, chromatin regulation, the JAK-STAT pathway, and the PI-3-K pathway. Remarkably, many of these deletions result from genomic rearrangements. Deletion of tumor suppressors HNRNPK and SOCS1 were the most frequent genetic alterations in MF after deletion of CDKN2A. Notably, SOCS1 deletion could be detected in early-stage MF. In agreement with the observed genomic alterations, transcriptome analysis revealed up-regulation of the cell cycle, JAK-STAT, PI-3-K and developmental pathways. Our results position inactivation of HNRNPK and SOCS1 as potential driver events in MF development.