Platelet-derived growth factor mediates survival of leukemic large granular lymphocytes via an autocrine regulatory pathway

Abstract

IntroductionLarge granular lymphocyte (LGL) leukemia is a lymphoproliferative disease of either CD3 ϩ cytotoxic T lymphocytes (CTLs) or CD3 Ϫ natural killer cells (NK cells). The majority of LGL patients with T-cell (CD3 ϩ , CD8 ϩ /CD57 ϩ ) or NK-cell (CD3 Ϫ , CD16 ϩ / CD56 ϩ ) leukemia have a clinically indolent course. 1,2 LeukemicLGLs of T-cell phenotype reflect polarized expansion of CD8 ϩ terminal-effector memory cells. 3 Expanded NK cells have an activated phenotype with dysregulated NK receptor expression. 4,5 Fas resistance is an important biologic feature in leukemic LGLs of both T-cell and NK-cell type. 3,6 Constitutive activation of survival signaling pathways is a central pathogenetic mechanism in LGL leukemia. Previously, phosphatidylinositol-3 (PI3) kinase activation and signal transducer and activator of transcription 3 upregulation of Mcl-1 were shown to be important for survival of leukemic T-LGLs. [7][8][9] More recently, molecular profiling of T-LGL leukemia revealed a survival role for constitutive sphingolipid signaling. 10 Survival mechanisms in the NK type of LGL leukemia have been less extensively studied; however, a constitutively active retrovirus-associated DNA sequence (RAS)/mitogen-activated protein kinase (MEK)/extracellular signal-related kinase (ERK) survival pathway was identified. 6 Given the complexity and interactive nature of signaling pathways, it is difficult to determine the importance of individual pathway components when studied in isolation. Using a network modeling approach, we found that the presence of interleukin-15 (IL-15) and platelet-derived growth factor (PDGF) is sufficient to reproduce all known deregulations in T-LGL leukemia. 11 Work in this study focused on further examining the pivotal role of PDGF. We found that PDGF mediates survival of leukemic LGLs of both T-and NK-cell origin through an autocrine regulatory pathway. Methods ReagentsAll chemicals were purchased from Sigma-Aldrich unless otherwise specified. Recombinant human (rh) PDGF-BB was purchased from ProSpec-TANY TechnoGene LTD; rhIL-2, from Promega Corporation; and human T-lymphotropic virus-I (HTLV-I)-and HTLV-II-infected plasma, from Zeptometrix. Antibodies and inhibitors were obtained from the following sources and used at the dilutions recommended by the manufacturers: anti-PDGFR-␣ (951) and anti-PDGFR-␤ (958) polyclonal antibodies, anti-phospho-Tyr monoclonal antibody (PY99), goat anti-mouse immunoglobulin G (IgG) antibody (Santa Cruz Biotechnology Inc); anti-PDGF-BB neutralizing antibody and anti-PDGF-BB antibody for immunocytochemistry/immunofluorescence (ICC/IF; Abcam Inc); anti-phospho-AKT and total AKT polyclonal antibodies, anti-MEK1/2, anti-phospho-MEK1/2, anti-ERK1/2, and phospho-ERK1/2 (Cell Signaling Technology); antiphospho-Src (Tyr419) and anti-Src antibodies (Upstate Cell Signaling Solutions); ␤-actin monoclonal antibody (Sigma-Aldrich); mouse antiglyceraldehyde-3-phosphate dehydrogenase (GAPDH) monoclonal antibody (Chemicon International); PI3K inhibitor LY294002 (Cell Signali...

Off-target effects of tyrosine kinase inhibitors: Beauty or the Beast?

“…IL-15 has been shown to be important for T-cell activation and generation of CD8þ memory cells [12,13]. PDGF is also a master switch controlling leukemic LGL survival [11,14]. This study reinforces the concept that both pro-and anti-activation signals are needed for CTL expansion and persistence [11].…”

Białaczki z dużych ziarnistych limfocytów T i komórek naturalnej cytotoksyczności

“…Płytkopochodny czynnik wzrostu jest najsilniejszym czynnikiem wzrostu dla komórek T i NK w białaczce T/NK--LGL. Obok IL-15 odgrywa kluczową rolę w patogenezie w białaczce T-LGL, regulując przeżywal-ność komórek poprzez szlaki sygnałowe PI3K-AKT i MEK/ERK [36].…”

New molecular insights into peripheral T cell lymphomas

“…Our group also found that the activation of PDGFRA is sustained by an autocrine stimulation, a mechanism subsequently found also in T-LGL (ref. 58 and Pileri, personal communication). Notably, PDGFR overexpression was later demonstrated in other T/NK-derived tumors, further strengthening its potential therapeutic relevance (see below) (30).…”