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Abstract
Sézary syndrome, the leukemic variant of cutaneous T-cell lymphoma, is still an enigmatic
disease with a fatal prognosis. Recent research, however, has identified a multitude
of dysregulated molecular pathways that contribute to malignant transformation and
therapy resistance of Sézary cells (SC). With respect to T-cell development, SC either
represent naive T cells, T effector memory or T central memory cells. Functionally,
SC may differentiate into Th2, Treg, or even Th17 cells. Despite their plasticity,
SC express characteristic diagnostic marker proteins including CD158k, CD164, FcRL3,
and PD-1 as well as skin-homing receptors such as CLA and CCR4. Already tested in
(pre)clinical trials, CD158k, PD-1, CTLA-4, and CCR4 also represent promising therapeutic
targets. Molecular alterations in SC include transcription factors such as STAT3,
4, and 5, as well as TWIST1 and TOX. TWIST1 induces expression of DNM3os containing
the miR-199a2/214 cluster, a key hub controlling multiple cancer networks. In addition,
activation of NFκB and the MAPK pathway as well as altered TCR signaling cause apoptosis
resistance. Recently, whole genome and exome sequencing has revealed somatic copy
number variations as predominant mutations in SC, primarily affecting apoptosis, NFκB
signaling, DNA integrity, and T-cell activation. In order to facilitate development
of novel therapies, improved in vivo models, which better reflect the pathogenesis
and clinical course of Sézary syndrome, are currently being generated.
Primary cutaneous lymphomas are currently classified by the European Organization for Research and Treatment of Cancer (EORTC) classification or the World Health Organization (WHO) classification, but both systems have shortcomings. In particular, differences in the classification of cutaneous T-cell lymphomas other than mycosis fungoides, Sezary syndrome, and the group of primary cutaneous CD30+ lymphoproliferative disorders and the classification and terminology of different types of cutaneous B-cell lymphomas have resulted in considerable debate and confusion. During recent consensus meetings representatives of both systems reached agreement on a new classification, which is now called the WHO-EORTC classification. In this paper we describe the characteristic features of the different primary cutaneous lymphomas and other hematologic neoplasms frequently presenting in the skin, and discuss differences with the previous classification schemes. In addition, the relative frequency and survival data of 1905 patients with primary cutaneous lymphomas derived from Dutch and Austrian registries for primary cutaneous lymphomas are presented to illustrate the clinical significance of this new classification.
The ISCL/EORTC recommends revisions to the Mycosis Fungoides Cooperative Group classification and staging system for cutaneous T-cell lymphoma (CTCL). These revisions are made to incorporate advances related to tumor cell biology and diagnostic techniques as pertains to mycosis fungoides (MF) and Sézary syndrome (SS) since the 1979 publication of the original guidelines, to clarify certain variables that currently impede effective interinstitution and interinvestigator communication and/or the development of standardized clinical trials in MF and SS, and to provide a platform for tracking other variables of potential prognostic significance. Moreover, given the difference in prognosis and clinical characteristics of the non-MF/non-SS subtypes of cutaneous lymphoma, this revision pertains specifically to MF and SS. The evidence supporting the revisions is discussed as well as recommendations for evaluation and staging procedures based on these revisions.
The skin of an adult human contains about 20 billion memory T cells. Epithelial barrier tissues are infiltrated by a combination of resident and recirculating T cells in mice, but the relative proportions and functional activities of resident versus recirculating T cells have not been evaluated in human skin. We discriminated resident from recirculating T cells in human-engrafted mice and lymphoma patients using alemtuzumab, a medication that depletes recirculating T cells from skin, and then analyzed these T cell populations in healthy human skin. All nonrecirculating resident memory T cells (TRM) expressed CD69, but most were CD4(+), CD103(-), and located in the dermis, in contrast to studies in mice. Both CD4(+) and CD8(+) CD103(+) TRM were enriched in the epidermis, had potent effector functions, and had a limited proliferative capacity compared to CD103(-) TRM. TRM of both types had more potent effector functions than recirculating T cells. We observed two distinct populations of recirculating T cells, CCR7(+)/L-selectin(+) central memory T cells (TCM) and CCR7(+)/L-selectin(-) T cells, which we term migratory memory T cells (TMM). Circulating skin-tropic TMM were intermediate in cytokine production between TCM and effector memory T cells. In patients with cutaneous T cell lymphoma, malignant TCM and TMM induced distinct inflammatory skin lesions, and TMM were depleted more slowly from skin after alemtuzumab, suggesting that TMM may recirculate more slowly. In summary, human skin is protected by four functionally distinct populations of T cells, two resident and two recirculating, with differing territories of migration and distinct functional activities.
Title:
JDDG: Journal der Deutschen Dermatologischen Gesellschaft
Abbreviated Title:
JDDG: Journal der Deutschen Dermatologischen Gesellschaft
Publisher:
Wiley
ISSN: 16100379
Publication date Created:
March
2016
Publication date
(Print):
March
2016
Publication date
(Electronic):
March
12 2016
Volume: 14
Issue: 3
Pages: 256-264
Affiliations
[1
]Department of Dermatology, Venereology and Allergology; University Medical Center
and Medical Faculty Mannheim; University of Heidelberg; Mannheim Germany
[2
]Department of Immunogenetics; German Cancer Research Center; Heidelberg Germany
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