A diagnostic challenge of KIT p.V559D and BRAF p.G469A mutations in a paragastric mass.

A patient with gastrointestinal stroma tumor (GIST) and KIT p.V559D and BRAF p.G469A alterations was referred to our institutional molecular tumor board (MTB) to discuss therapeutic implications. The patient had been diagnosed with B-cell chronic lymphocytic leukemia (CLL) years prior to the MTB presentation. GIST had been diagnosed 1 month earlier. After structured clinical annotation of the molecular alterations and interdisciplinary discussion, we considered BRAF/KIT co-mutation unlikely in a treatment-naïve GIST. Discordant variant allele frequencies furthermore suggested a second malignancy. NGS of a CLL sample revealed the identical class 2 BRAF alteration, thus supporting admixture of CLL cells in the paragastric mass, leading to the detection of 2 alterations. Following the MTB recommendation, the patient received imatinib and had a radiographic response. Structured annotation and interdisciplinary discussion in specialized tumor boards facilitate the clinical management of complex molecular findings. Coexisting malignancies and clonal hematopoiesis warrant consideration in case of complex and uncommon molecular findings.

[Detection of BRAF V600E mutation in metastatic colorectal carcinoma : A QuIP round robin test]. / Nachweis der BRAF-V600E-Mutation beim metastasierten kolorektalen Karzinom : Ein QuIP-Ringversuch.

Round robin testing is an important instrument for quality assurance. Increasingly, this also applies to the results of molecular diagnostics in pathology, which directly influence therapy decisions in precision oncology. In metastatic colorectal carcinoma (mCRC), the focus has been on detecting KRAS and NRAS mutations, whose absence allows therapy with EGFR blocking antibodies. Recently, BRAF has been added as another predictive marker, since mCRC patients with BRAF V600E mutation benefit significantly from treatment with encorafenib (a BRAF inhibitor) in combination with cetuximab (anti-EGFR antibody) after systemic therapy. Due to the approval of this treatment in 2020, it is a pre-requisite that BRAF V600E mutation detection in diagnostic pathologies is reliably performed. Therefore, this round robin test with BRAF V600E testing either by immunohistochemistry or molecular methods was performed. The round robin test results demonstrate that molecular BRAF V600E detection is currently clearly superior to immunohistochemical detection.

The majority of ß-catenin mutations in colorectal cancer is homozygous.

BACKGROUND: ß-catenin activation plays a crucial role for tumourigenesis in the large intestine but except for Lynch syndrome (LS) associated cancers stabilizing mutations of ß-catenin gene (CTNNB1) are rare in colorectal cancer (CRC). Previous animal studies provide an explanation for this observation. They showed that CTNNB1 mutations induced transformation in the colon only when CTNNB1 was homozygously mutated or when membranous ß-catenin binding was hampered by E-cadherin haploinsufficiency. We were interested, if these mechanisms are also found in human CTNNB1 mutated CRCs. RESULTS: Among 869 CRCs stabilizing CTNNB1 mutations were found in 27 cases. Homo- or hemizygous CTNNB1 mutations were detected in 74% of CTNNB1 mutated CRCs (13 microsatellite instabile (MSI-H), 7 microsatellite stabile (MSS)) but only in 3% (1/33) of extracolonic CTNNB1 mutated cancers. In contrast to MSS CRC, CTNNB1 mutations at codon 41 or 45 were highly selected in MSI-H CRC. Of the examined three CRC cell lines, ß-catenin and E-cadherin expression was similar in cell lines without or with hetereozygous CTNNB1 mutations (DLD1 and HCT116), while a reduced E-cadherin expression combined with cytoplasmic accumulation of ß-catenin was found in a cell line with homozygous CTNNB1 mutation (LS180). Reduced expression of E-cadherin in human MSI-H CRC tissue was identified in 60% of investigated cancers, but no association with the CTNNB1 mutational status was found. CONCLUSIONS: In conclusion, this study shows that in contrast to extracolonic cancers stabilizing CTNNB1 mutations in CRC are commonly homo- or hemizygous indicating a higher threshold of ß-catenin stabilization to be required for transformation in the colon as compared to extracolonic sites. Moreover, we found different mutational hotspots in CTNNB1 for MSI-H and MSS CRCs suggesting a selection of different effects on ß-catenin stabilization according to the molecular pathway of tumourigenesis. Reduced E-cadherin expression in CRC may further contribute to higher levels of transcriptionally active ß-catenin, but it is not directly linked to the CTNNB1 mutational status.

Correction to: The majority of ß-catenin mutations in colorectal cancer is homozygous.

An amendment to this paper has been published and can be accessed via the original article.

Dimethyl fumarate restores apoptosis sensitivity and inhibits tumor growth and metastasis in CTCL by targeting NF-κB.

Despite intensive efforts in recent years, a curative therapy for cutaneous T-cell lymphoma (CTCL) has not yet been developed. Therefore, the establishment of new therapeutic approaches with higher efficacy rates and milder side effects is strongly desired. A characteristic feature of the malignant T-cell population in CTCL is resistance toward cell death resulting from constitutive NF-κB activation. Therefore, NF-κB-dependent cell death resistance represents an interesting therapeutic target in CTCL because an NF-κB-directed therapy would leave bystander T cells widely unaffected. We investigated the effects of dimethyl fumarate (DMF) on CTCL cells in vitro and in vivo. DMF induced cell death in primary patient-derived CD4(+) cells and CTCL cell lines, but hardly in T cells from healthy donors. DMF-induced cell death was linked specifically to NF-κB inhibition. To study the impact of DMF in vivo, we developed 2 CTCL xenograft mouse models with different cutaneous localizations of the T-cell infiltrate. DMF treatment delayed the growth of CTCL tumors and prevented formation of distant metastases. In addition, DMF induced increased cell death in primary CTCL tumors and in liver metastases. In summary, DMF treatment represents a remarkable therapeutic option in CTCL because it restores CTCL apoptosis in vitro and in preclinical models in vivo and prevents spreading of the disease to distant sites. DMF treatment is of particular promise in CTCL because DMF is already in successful clinical use in the treatment of psoriasis and multiple sclerosis allowing fast translation into clinical studies in CTCL.

Mechanisms of Targeting the MDM2-p53-FOXM1 Axis in Well-Differentiated Intestinal Neuroendocrine Tumors.

BACKGROUND/AIMS: The tumor suppressor p53 is rarely mutated in gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) but they frequently show a strong expression of negative regulators of p53, rendering these tumors excellent targets for a p53 recovery therapy. Therefore, we analyzed the mechanisms of a p53 recovery therapy on intestinal neuroendocrine tumors in vitro and in vivo. METHODS: By Western blot and immunohistochemistry, we found that in GEP-NEN biopsy material overexpression of MDM2 was present in intestinal NEN. Therefore, we analyzed the effect of a small-molecule inhibitor, nutlin-3a, in p53 wild-type and mutant GEP-NEN cell lines by proliferation assay, flow cytometry, immunofluorescence, Western blot, and by multiplex gene expression analysis. Finally, we analyzed the antitumor effect of nutlin-3a in a xenograft mouse model in vivo. During the study, the tumor volume was determined. RESULTS: The midgut wild-type cell line KRJ-I responded to the treatment with cell cycle arrest and apoptosis. By gene expression analysis, we could demonstrate that nutlins reactivated an antiproliferative p53 response. KRJ-I-derived xenograft tumors showed a significantly decreased tumor growth upon treatment with nutlin-3a in vivo. Furthermore, our data suggest that MDM2 also influences the expression of the oncogene FOXM1 in a p53-independent manner. Subsequently, a combined treatment of nutlin-3a and cisplatin (as chemoresistance model) resulted in synergistically enhanced antiproliferative effects. CONCLUSION: In summary, MDM2 overexpression is a frequent event in p53 wild-type intestinal neuroendocrine neoplasms and therefore recovery of a p53 response might be a novel personalized treatment approach in these tumors.

The Effects of Arsenic Trioxide in Combination with Retinoic Acids on Cutaneous T-Cell Lymphoma Cell Lines.

Cutaneous T-cell lymphomas (CTCL) are characterized by an infiltration of the skin with malignant T cells. Curative treatments for aggressive entities such as Sézary syndrome have not been identified yet. Arsenic trioxide (AsO3) is used for the treatment of acute promyelocytic leukemia in combination with retinoids. As the latter are established treatment options in CTCL, we sought to evaluate the efficacy of AsO3 for mono- and combination therapy in vitro. Analyses for apoptosis, cell cycle inhibition, cytotoxicity and cell viability were made after incubation of CTCL cells with AsO3 alone or in combination with the retinoids all-trans-retinoic acid or bexarotene. While AsO3 induced apoptosis, retinoids did not at the time point of analysis. However, retinoids strongly reduced cell viability. Due to the efficient apoptosis induction, AsO3 might be a potentially suitable agent for CTCL treatment, although this effect was not increased by retinoids.

Evaluation of blood parameters for the monitoring of erythrodermic cutaneous T-cell lymphoma.

BACKGROUND AND OBJECTIVES: Erythrodermic cutaneous T-cell lymphomas are aggressive diseases posing diagnostic and therapeutic challenges. Numerous indicators for confirming diagnosis and disease-monitoring have been proposed. CD26-negativity of peripheral CD4+ T-cells has been reported to have these properties. Our aim was to test, if the CD4(+) T-cell count, fraction of CD26- or CD7-negative CD4+ T-cells during the course of disease are valuable markers to predict therapeutic efficacy or disease progression in relation to changes in skin status. PATIENTS AND METHODS: Retrospective cohort analysis of eleven patients treated at a tertiary referral centre. Statistics were done by linear regression analysis and logrank test. RESULTS: Five patients displayed response to therapy in the skin, nine in the blood. Patients with cutaneous response showed a decrease of CD4+ T-cells, preceding the clinical response in most patients, whereas the percentage of CD26-negative T-cells changed first during clinical improvement. The calculated positive predictive values for response or progression were low for both CD4-count and CD26-expression. CONCLUSIONS: CD26 is not a reliable marker of either response or progression. As cutaneous response was always associated with a response in blood and not vice versa, we conclude, that the clinical status represents the most important parameter for guiding therapeutic decisions.

T-cell receptor gene rearrangement analysis of sequential biopsies in cutaneous T-cell lymphomas with the Biomed-2 PCR reveals transient T-cell clones in addition to the tumor clone.

Detection of a dominant T-cell clone by T-cell receptor (TCR) gene rearrangement analysis is often essential for the diagnosis of cutaneous T-cell lymphomas (CTCL). The occurrence of T-cell clones in addition to the diagnostic T-cell clone during the course of CTCL has been reported, but the data of these studies have been contradictory. We retrospectively evaluated the data of 114 lesional skin biopsies from 26 patients with Mycosis fungoides and two patients with primary cutaneous anaplastic large cell lymphoma, which were analysed with the standardized Biomed-2 PCR for the TCRγ and TCRß locus. A dominant T-cell clone was repetitively detected in 93% (26/28) of patients. Additional T-cell clones appeared temporarily in 39% (11/28) of patients. Correlation with the clinical data did not show an association of the presence of additional T-cell clones with age, number of treatments, progression of disease or survival. Our findings demonstrate that a persistent T-cell clone, most likely the disease causing tumor clone, is detectable in almost all CTCL patients. In addition, transiently appearing T-cell clones frequently occur during the course of disease. The biological relevance of these additional clones has still to be determined. However, it is important to take the possibility of additional T-cell clones into account for diagnostic analyses.

EuroClonality-NGS Recommendations for Evaluation of B-Cell Clonality Analysis by Next-Generation Sequencing: A Structured Approach with the DEPART Algorithm.

Next-generation sequencing (NGS)-based clonality analysis allows in-depth assessment of the clonal composition of a sample with high sensitivity for detecting small clones. Within the EuroClonality-NGS Working Group, a protocol for NGS Ig clonality analysis was developed and validated previously. This NGS-based approach was designed to generate small amplicons, making it suitable for samples with suboptimal DNA quality, especially material derived from formalin-fixed, paraffin-embedded tissue. Using expert assessment of NGS Ig clonality results as a reference, a structured algorithmic approach to the assessment of NGS-amplicon-based B-cell clonality analysis was developed. A structured approach with the Detection of clonality through Evaluation of sample quality and assessment of Pattern, Abundance and RaTio (DEPART) algorithm was proposed, which consecutively evaluates sample quality, the pattern of the clonotypes present, the abundance of the most dominant clonotypes, and the ratio between the dominant clonotypes and the background to evaluate the different Ig gene targets. Specific issues with respect to evaluation of the various Ig targets as well as the integration of results of individual targets into a molecular clonality conclusion are discussed and illustrated with case examples. Finally, the importance of interpretation of NGS-based clonality results in clinical and histopathologic contexts is discussed. It is expected that these recommendations will have clinical utility to facilitate proper evaluation of clonality assessment.

Decoding molecular programs in melanoma brain metastases.

Melanoma brain metastases (MBM) variably respond to therapeutic interventions; thus determining patient's prognosis. However, the mechanisms that govern therapy response are poorly understood. Here, we use a multi-OMICS approach and targeted sequencing (TargetSeq) to unravel the programs that potentially control the development of progressive intracranial disease. Molecularly, the expression of E-cadherin (Ecad) or NGFR, the BRAF mutation state and level of immune cell infiltration subdivides tumors into proliferative/pigmented and invasive/stem-like/therapy-resistant irrespective of the intracranial location. The analysis of MAPK inhibitor-naive and refractory MBM reveals switching from Ecad-associated into NGFR-associated programs during progression. NGFR-associated programs control cell migration and proliferation via downstream transcription factors such as SOX4. Moreover, global methylome profiling uncovers 46 differentially methylated regions that discriminate BRAFmut and wildtype MBM. In summary, we propose that the expression of Ecad and NGFR sub- classifies MBM and suggest that the Ecad-to-NGFR phenotype switch is a rate-limiting process which potentially indicates drug-response and intracranial progression states in melanoma patients.

Pathogenesis of Mycosis fungoides.

Mycosis fungoides is the most common type of primary cutaneous lymphomas. The phenotype of the tumor cell corresponds to an effector/memory-type of helper T cell which, given its repertoire of homing receptors, is specialized for recirculation through the skin. In recent years genetic analyses have uncovered various chromosomal aberrations in the tumour cells of mycosis fungoides. Their relevance to the pathogenesis and clinical appearance are discussed in the following.

Evaluation of a worldwide EQA scheme for complex clonality analysis of clinical lymphoproliferative cases demonstrates a learning effect.

Clonality analysis of immunoglobulin (IG) or T-cell receptor (TR) gene rearrangements is routine practice to assist diagnosis of lymphoid malignancies. Participation in external quality assessment (EQA) aids laboratories in identifying systematic shortcomings. The aim of this study was to evaluate laboratories' improvement in IG/TR analysis and interpretation during five EQA rounds between 2014 and 2018. Each year, participants received a total of five cases for IG and five cases for TR testing. Paper-based cases were included for analysis of the final molecular conclusion that should be interpreted based on the integration of the individual PCR results. Wet cases were distributed for analysis of their routine protocol as well as evaluation of the final molecular conclusion. In total, 94.9% (506/533) of wet tests and 97.9% (829/847) of paper tests were correctly analyzed for IG, and 96.8% (507/524) wet tests and 93.2% (765/821) paper tests were correctly analyzed for TR. Analysis scores significantly improved when laboratories participated to more EQA rounds (p=0.001). Overall performance was significantly lower (p=0.008) for non-EuroClonality laboratories (95% for IG and 93% for TR) compared to EuroClonality laboratories (99% for IG and 97% for TR). The difference was not related to the EQA scheme year, anatomic origin of the sample, or final clinical diagnosis. This evaluation showed that repeated EQA participation helps to reduce performance differences between laboratories (EuroClonality versus non-EuroClonality) and between sample types (paper versus wet). The difficulties in interpreting oligoclonal cases highlighted the need for continued education by meetings and EQA schemes.

Next-Generation Sequencing-Based Clonality Assessment of Ig Gene Rearrangements: A Multicenter Validation Study by EuroClonality-NGS.

Ig gene (IG) clonality analysis has an important role in the distinction of benign and malignant B-cell lymphoid proliferations and is mostly performed with the conventional EuroClonality/BIOMED-2 multiplex PCR protocol and GeneScan fragment size analysis. Recently, the EuroClonality-NGS Working Group developed a method for next-generation sequencing (NGS)-based IG clonality analysis. Herein, we report the results of an international multicenter biological validation of this novel method compared with the gold standard EuroClonality/BIOMED-2 protocol, based on 209 specimens of reactive and neoplastic lymphoproliferations. NGS-based IG clonality analysis showed a high interlaboratory concordance (99%) and high concordance with conventional clonality analysis (98%) for the molecular conclusion. Detailed analysis of the individual IG heavy chain and kappa light chain targets showed that NGS-based clonality analysis was more often able to detect a clonal rearrangement or yield an interpretable result. NGS-based and conventional clonality analysis detected a clone in 96% and 95% of B-cell neoplasms, respectively, and all but one of the reactive cases were scored polyclonal. We conclude that NGS-based IG clonality analysis performs comparable to conventional clonality analysis. We provide critical parameters for interpretation and discuss a first step toward a quantitative scoring approach for NGS clonality results. Considering the advantages of NGS-based clonality analysis, including its high sensitivity and possibilities for accurate clonal comparison, this supports implementation in diagnostic practice.

Mutational Diversity and Therapy Response in Breast Cancer: A Sequencing Analysis in the Neoadjuvant GeparSepto Trial.

PURPOSE: Next-generation sequencing (NGS) can be used for comprehensive investigation of molecular events in breast cancer. We evaluated the relevance of genomic alterations for response to neoadjuvant chemotherapy (NACT) in the GeparSepto trial. EXPERIMENTAL DESIGN: Eight hundred fifty-one pretherapeutic formalin-fixed paraffin-embedded (FFPE) core biopsies from GeparSepto study were sequenced. The panel included 16 genes for mutational (AKT1, BRAF, CDH1, EGFR, ERBB2, ESR1, FBXW7, FGFR2, HRAS, KRAS, NRAS, SF3B1, TP53, HNF1A, PIK3CA, and PTEN) and 8 genes for copy-number alteration analysis (CCND1, ERBB2, FGFR1, PAK1, PIK3CA, TOP2A, TP53, and ZNF703). RESULTS: The most common genomic alterations were mutations of TP53 (38.4%) and PIK3CA (21.5%), and 8 different amplifications (TOP2A 34.9%; ERBB2 30.6%; ZNF703 30.1%; TP53 21.9%; PIK3CA 24.1%; CCND1 17.7%; PAK1 14.9%; FGFR 12.6%). All other alterations had a prevalence of less than 5%. The genetic heterogeneity in different breast cancer subtypes [lum/HER2neg vs. HER2pos vs. triple-negative breast cancer (TNBC)] was significantly linked to differences in NACT response. A significantly reduced pathologic complete response rate was observed in PIK3CA-mutated breast cancer [PIK3CAmut: 23.0% vs. wild-type (wt) 38.8%, P < 0.0001] in particular in the HER2pos subcohort [multivariate OR = 0.43 (95% CI, 0.24-0.79), P = 0.006]. An increased response to nab-paclitaxel was observed only in PIK3CAwt breast cancer, with univariate significance for the complete cohort (P = 0.009) and the TNBC (P = 0.013) and multivariate significance in the HER2pos subcohort (test for interaction P = 0.0074). CONCLUSIONS: High genetic heterogeneity was observed in different breast cancer subtypes. Our study shows that FFPE-based NGS can be used to identify markers of therapy resistance in clinical study cohorts. PIK3CA mutations could be a major mediator of therapy resistance in breast cancer.

Next-generation sequencing of immunoglobulin gene rearrangements for clonality assessment: a technical feasibility study by EuroClonality-NGS.

One of the hallmarks of B lymphoid malignancies is a B cell clone characterized by a unique footprint of clonal immunoglobulin (IG) gene rearrangements that serves as a diagnostic marker for clonality assessment. The EuroClonality/BIOMED-2 assay is currently the gold standard for analyzing IG heavy chain (IGH) and κ light chain (IGK) gene rearrangements of suspected B cell lymphomas. Here, the EuroClonality-NGS Working Group presents a multicentre technical feasibility study of a novel approach involving next-generation sequencing (NGS) of IGH and IGK loci rearrangements that is highly suitable for detecting IG gene rearrangements in frozen and formalin-fixed paraffin-embedded tissue specimens. By employing gene-specific primers for IGH and IGK amplifying smaller amplicon sizes in combination with deep sequencing technology, this NGS-based IG clonality analysis showed robust performance, even in DNA samples of suboptimal DNA integrity, and a high clinical sensitivity for the detection of clonal rearrangements. Bioinformatics analyses of the high-throughput sequencing data with ARResT/Interrogate, a platform developed within the EuroClonality-NGS Working Group, allowed accurate identification of clonotypes in both polyclonal cell populations and monoclonal lymphoproliferative disorders. This multicentre feasibility study is an important step towards implementation of NGS-based clonality assessment in clinical practice, which will eventually improve lymphoma diagnostics.

Genome-Wide Analysis of Interchromosomal Interaction Probabilities Reveals Chained Translocations and Overrepresentation of Translocation Breakpoints in Genes in a Cutaneous T-Cell Lymphoma Cell Line.

In classical models of tumorigenesis, the accumulation of tumor promoting chromosomal aberrations is described as a gradual process. Next-generation sequencing-based methods have recently revealed complex patterns of chromosomal aberrations, which are beyond explanation by these classical models of karyotypic evolution of tumor genomes. Thus, the term chromothripsis has been introduced to describe a phenomenon, where temporarily and spatially confined genomic instability results in dramatic chromosomal rearrangements limited to segments of one or a few chromosomes. Simultaneously arising and misrepaired DNA double-strand breaks are also the cause of another phenomenon called chromoplexy, which is characterized by the presence of chained translocations and interlinking deletion bridges involving several chromosomes. In this study, we demonstrate the genome-wide identification of chromosomal translocations based on the analysis of translocation-associated changes in spatial proximities of chromosome territories on the example of the cutaneous T-cell lymphoma cell line Se-Ax. We have used alterations of intra- and interchromosomal interaction probabilities as detected by genome-wide chromosome conformation capture (Hi-C) to infer the presence of translocations and to fine-map their breakpoints. The outcome of this analysis was subsequently compared to datasets on DNA copy number alterations and gene expression. The presence of chained translocations within the Se-Ax genome, partly connected by intervening deletion bridges, indicates a role of chromoplexy in the etiology of this cutaneous T-cell lymphoma. Notably, translocation breakpoints were significantly overrepresented in genes, which highlight gene-associated biological processes like transcription or other gene characteristics as a possible cause of the observed complex rearrangements. Given the relevance of chromosomal aberrations for basic and translational research, genome-wide high-resolution analysis of structural chromosomal aberrations will gain increasing importance.

Establishment of the First Well-differentiated Human Pancreatic Neuroendocrine Tumor Model.

Clinical options for systemic therapy of neuroendocrine tumors (NET) are limited. Development of new drugs requires suitable representative in vitro and in vivo model systems. So far, the unavailability of a human model with a well-differentiated phenotype and typical growth characteristics has impaired preclinical research in NET. Herein, we establish and characterize a lymph node-derived cell line (NT-3) from a male patient with well-differentiated pancreatic NET. Neuroendocrine differentiation and tumor biology was compared with existing NET cell lines BON and QGP-1. In vivo growth was assessed in a xenograft mouse model. The neuroendocrine identity of NT-3 was verified by expression of multiple NET-specific markers, which were highly expressed in NT-3 compared with BON and QGP-1. In addition, NT-3 expressed and secreted insulin. Until now, this well-differentiated phenotype is stable since 58 passages. The proliferative labeling index, measured by Ki-67, of 14.6% ± 1.0% in NT-3 is akin to the original tumor (15%-20%), and was lower than in BON (80.6% ± 3.3%) and QGP-1 (82.6% ± 1.0%). NT-3 highly expressed somatostatin receptors (SSTRs: 1, 2, 3, and 5). Upon subcutaneous transplantation of NT-3 cells, recipient mice developed tumors with an efficient tumor take rate (94%) and growth rate (139% ± 13%) by 4 weeks. Importantly, morphology and neuroendocrine marker expression of xenograft tumors resembled the original human tumor.Implications: High expression of somatostatin receptors and a well-differentiated phenotype as well as a slow growth rate qualify the new cell line as a relevant model to study neuroendocrine tumor biology and to develop new tumor treatments. Mol Cancer Res; 16(3); 496-507. ©2018 AACR.

IL-32 induces indoleamine 2,3-dioxygenase+CD1c+ dendritic cells and indoleamine 2,3-dioxygenase+CD163+ macrophages: Relevance to mycosis fungoides progression.

Mycosis fungoides (MF) progresses from patch to tumor stage by expansion of malignant T-cells that fail to be controlled by protective immune mechanisms. In this study, we focused on IL-32, a cytokine, highly expressed in MF lesions. Depending on the other cytokines (IL-4, GM-CSF) present during in vitro culture of healthy volunteers' monocytes, IL-32 increased the maturation of CD11c+ myeloid dendritic cells (mDC) and/or CD163+ macrophages, but IL-32 alone showed a clear ability to promote dendritic cell (DC) differentiation from monocytes. DCs matured by IL-32 had the phenotype of skin-resident DCs (CD1c+), but more importantly, also had high expression of indoleamine 2,3-dioxygenase. The presence of DCs with these markers was demonstrated in MF skin lesions. At a molecular level, indoleamine 2,3-dioxygenase messenger RNA (mRNA) levels in MF lesions were higher than those in healthy volunteers, and there was a high correlation between indoleamine 2,3-dioxygenase and IL-32 expression. In contrast, Foxp3 mRNA levels decreased from patch to tumor stage. Increasing expression of IL-10 across MF lesions was highly correlated with IL-32 and indoleamine 2,3-dioxygenase, but not with Foxp3 expression. Thus, IL-32 could contribute to progressive immune dysregulation in MF by directly fostering development of immunosuppressive mDC or macrophages, possibly in association with IL-10.