Constitutive activation of WASp leads to abnormal cytotoxic cells with increased granzyme B and degranulation response to target cells.

Joanna S Kritikou,Anton Sendel,Saket M Nigam,Lisa S Westerberg,Klas Kärre,Jordan S Orange,Stamatina Rentouli,Peter Vandenberghe,Hanna Brauner,Saikiran K Sedimbi,Scott B Snapper,Marton Keszei,David P Lane,Julien Record,Minghui He,Mariana M.S Oliveira,Mezida B Saeed,Arnika K Wagner

doi:10.1172/jci.insight.140273

Abstract

X-linked neutropenia (XLN) is caused by gain-of-function mutations in the actin regulator Wiskott-Aldrich Syndrome protein (WASp). XLN patients have reduced numbers of cytotoxic cells in peripheral blood; however, their capacity to kill tumor cells remains to be determined. Here, we examined NK and T cells from 2 patients with XLN harboring the activating WASpL270P mutation. XLN patient NK and T cells had increased granzyme B content and elevated degranulation and IFN-γ production when compared with healthy control cells. Murine WASpL272P NK and T cells formed stable synapses with YAC-1 tumor cells and anti-CD3/CD28–coated beads, respectively. WASpL272P mouse T cells had normal degranulation and cytokine response whereas WASpL272P NK cells showed an enhanced response. Imaging experiments revealed that while WASpL272P CD8+ T cells had increased accumulation of actin upon TCR activation, WASpL272P NK cells had normal actin accumulation at lytic synapses triggered through NKp46 signaling but had impaired response to lymphocyte function associated antigen-1 engagement. When compared with WT mice, WASpL272P mice showed reduced growth of B16 melanoma and increased capacity to reject MHC class I–deficient cells. Together, our data suggest that cytotoxic cells with constitutively active WASp have an increased capacity to respond to and kill tumor cells.

Highlights

Patients with X-linked neutropenia (XLN) have severe congenital neutropenia, recurrent infections, and a higher susceptibility to developing hematological malignancies [1, 2]
To assess the effector potential of the XLN patient lymphocytes, we examined the expression of the effector molecule granzyme B by flow cytometry and by imaging flow cytometry in natural killer (NK) and T cells
Studies of Wiskott-Aldrich Syndrome protein (WASp)-deficient NK cells and CTLs have revealed the important role for WASp-mediated actin dynamics in cytotoxic cells for eradication of tumor cells [15, 30,31,32,33,34]

Summary

Introduction

Patients with X-linked neutropenia (XLN) have severe congenital neutropenia, recurrent infections, and a higher susceptibility to developing hematological malignancies [1, 2]. As predicted from biochemical studies of WASp and the close homolog neuronal WASp (N-WASp) [5], XLN mutations induce increased phosphorylation of a critical tyrosine-291 (murine tyrosine-293), even in the absence of receptor activation [11]. Neutrophils and B and T cells expressing XLN mutations in WASp show increased F-actin content and decreased capacity to form firm adhesion upon receptor activation [2, 10,11,12, 15]. XLN mutations lead to genomic instability of B cells and myeloid cells, likely caused by accumulation of F-actin during cytokinesis, increased mechanical stress at the kinetochore, and activation of Aurora B kinase error correction [10, 12, 16]. While mice devoid of WASp expression had earlier tumor onset and mortality, we found surprisingly in the context of genomic instability of XLN B cells that XLN mice show delayed tumor onset when compared with WT mice [15]

Methods

Results

Conclusion