JAK3 Is Expressed in the Nucleus of Malignant T Cells in Cutaneous T Cell Lymphoma (CTCL).

Chella Krishna Vadivel,Lasse Boding,Charlotte M Bonefeld,Sara Torres-Rusillo,Carsten Geisler,Tea Kirkegaard Nielsen,Terkild B Buus,Niels Odum,Anja T Fuglsang,Andreas Willerslev-Olsen,Maria Gluud,Thorbjorn Krejsgaard,Anders Woetmann,Jenny L Persson

doi:10.3390/cancers13020280

Abstract

Simple SummaryJAK3 plays an important role in the pathogenesis of cutaneous T cell lymphoma. JAK3 belongs to the Janus kinase family of receptor-associated tyrosine kinases located in cytoplasm adjacent to the plasma membrane. In this study, we show that JAK3 can also be ectopically expressed in the nucleus in CTCL cell lines and primary cells from CTCL patients. Importantly, JAK3 interacts with the nuclear protein RNA polymerase II and phosphorylates Histone H3. Thus, our data provide first evidence for nuclear expression of JAK3 and interactions with key nuclear proteins in malignant T cells suggesting a novel non-canonical role in CTCL.Perturbation in JAK-STAT signaling has been reported in the pathogenesis of cutaneous T cell lymphoma (CTCL). JAK3 is predominantly associated with the intra-cytoplasmic part of IL-2Rγc located in the plasma membrane of hematopoietic cells. Here we demonstrate that JAK3 is also ectopically expressed in the nucleus of malignant T cells. We detected nuclear JAK3 in various CTCL cell lines and primary malignant T cells from patients with Sézary syndrome, a leukemic variant of CTCL. Nuclear localization of JAK3 was independent of its kinase activity whereas STAT3 had a modest effect on nuclear JAK3 expression. Moreover, JAK3 nuclear localization was only weakly affected by blockage of nuclear export. An inhibitor of the nuclear export protein CRM1, Leptomycin B, induced an increased expression of SOCS3 in the nucleus, but only a weak increase in nuclear JAK3. Importantly, immunoprecipitation experiments indicated that JAK3 interacts with the nuclear protein POLR2A, the catalytic subunit of RNA Polymerase II. Kinase assays showed tyrosine phosphorylation of recombinant human Histone H3 by JAK3 in vitro—an effect which was blocked by the JAK inhibitor (Tofacitinib citrate). In conclusion, we provide the first evidence of nuclear localization of JAK3 in malignant T cells. Our findings suggest that JAK3 may have a cytokine-receptor independent function in the nucleus of malignant T cells, and thus a novel non-canonical role in CTCL.

Highlights

Cutaneous T cell lymphoma (CTCL) is a haematological cancer where clonally expanded malignant T cells accumulate in the skin leading to chronically inflamed skin lesions [1,2,3,4,5]
To confirm the relevance of Janus Kinase 3 (JAK3) inhibition in the present cellular context, MyLa2059 cells were treated with JAK3 inhibitor or vehicle control and the fold change in mRNA expression in vehicleto-JAK3 inhibitor-treated cells is shown confirming that JAK3 regulates expression of these genes in MyLa2059 cells (Table S1)
Since STAT3 knockdown had a modest effect on nuclear localization of JAK3 in malignant cells, and because we predicted a potential NES sequence in JAK3, we addressed whether Leptomycin B regulated JAK3 nuclear expression like STAT3

Summary

Introduction

Cutaneous T cell lymphoma (CTCL) is a haematological cancer where clonally expanded malignant T cells accumulate in the skin leading to chronically inflamed skin lesions [1,2,3,4,5]. Single-cell sequencing has revealed a high level of disease heterogeneity—both between patients (inter-patient heterogeneity) and in the individual patient (intra-patient heterogeneity) [7] indicating that individual patients harbour highly heterogeneous populations of malignant T cells [7,8] which has been confirmed by immunohistochemistry and analyses of separate lesions derived from the same patient [9,10]. Other genetic studies have indicated that CTCL is a highly heterogeneous disease and is not driven by a single somatic mutation [11,12]

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