Whole Genome Sequencing of Spontaneously Occurring Rat Natural Killer Large Granular Lymphocyte Leukemia Identifies JAK1 Somatic Activating Mutation.

T Tiffany Wang,Suna Onengut-Gumuscu,Thomas P Loughran,Matthew W Schmachtenberg,Thomas L Olson,Nathan T Leigh,Shubha Dighe,Aakrosh Ratan,Jun Yang,David J Feith,Emily Farber

doi:10.3390/cancers12010126

Abstract

Large granular lymphocyte (LGL) leukemia arises spontaneously in elderly Fischer (F344) rats. This rodent model has been shown to emulate many aspects of the natural killer (NK) variant of human LGL leukemia. Previous transplantation of leukemic material into young F344 rats resulted in several strains of rat NK (RNK) primary leukemic cells. One strain, RNK-16, was adapted into the RNK-16 cell line and established as an aggressive NK-LGL leukemia model. Whole genome sequencing of the RNK-16 cell line identified 255,838 locations where the RNK16 had an alternate allele that was different from F344, including a mutation in Jak1. Functional studies showed Jak1 Y1034C to be a somatic activating mutation that mediated increased STAT signaling, as assessed by phosphoprotein levels. Sanger sequencing of Jak1 in RNK-1, -3, -7, and -16 found only RNK-16 to harbor the Y1034C Jak1 mutation. In vivo studies revealed that rats engrafted with RNK-16 primary material developed leukemia more rapidly than those engrafted with RNK-1, -3, and -7. Additionally, ex vivo RNK-16 spleen cells from leukemic rats exhibited increased STAT1, STAT3, and STAT5 phosphorylation compared to other RNK strains. Therefore, we report and characterize a novel gain-of-function Jak1 mutation in a spontaneous LGL leukemia model that results in increased downstream STAT signaling.

Highlights

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative neoplasm characterized by uncontrolled clonal expansion of LGLs of T-cell or natural killer (NK) cell origin, which causes anemia, neutropenia, and splenomegaly [1]
Whole genome sequencing (WGS) was successfully performed on the rat NK (RNK)-16 cell line in an effort to identify variants that contribute to NK cell leukemogenesis (Figure 1)
We found that rats transplanted with RNK-16 have significantly more rapid disease development

Summary

Introduction

Large granular lymphocyte (LGL) leukemia is a lymphoproliferative neoplasm characterized by uncontrolled clonal expansion of LGLs of T-cell or natural killer (NK) cell origin, which causes anemia, neutropenia, and splenomegaly [1]. The World Health Organization classified LGL leukemia into three subtypes: T-cell LGL leukemia, chronic lymphoproliferative disorder of NK cells, and aggressive. The aggressive NK-cell leukemia is distinct from its indolent counterparts, affecting younger individuals with a higher prevalence in Asia and South America [3,4]. While the etiology of LGL leukemia is not well understood, LGL leukemia is characterized by multiple aberrant signaling pathways, including the Janus kinase/signal transducers and activators of the transcription (JAK/STAT) signaling pathway [1,5]. The JAK/STAT pathway relays extracellular signals from cytokines and other factors to intracellular factors to control nuclear transcription. This pathway is essential for various intracellular processes, including apoptosis, immune response, and differentiation. JAK proteins consist of four domains; an N-terminal FERM (F for 4.1 protein, E for ezrin, R for radixin and M for moesin) domain, an SH2 domain, a pseudokinase domain, and a C-terminal protein tyrosine kinase (PTK)

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