Blocking KCa3.1 Channels Increases Tumor Cell Killing by a Subpopulation of Human Natural Killer Lymphocytes

Shyny Koshy,Christine Beeton,Patricia Yotnda,Rajeev B Tajhya,Michael W Pennington,Xueyou Hu,Heike Wulff,Redwan Huq,Fatima S Khan,Danli Wu

doi:10.1371/journal.pone.0076740

Abstract

Natural killer (NK) cells are large granular lymphocytes that participate in both innate and adaptive immune responses against tumors and pathogens. They are also involved in other conditions, including organ rejection, graft-versus-host disease, recurrent spontaneous abortions, and autoimmune diseases such as multiple sclerosis. We demonstrate that human NK cells express the potassium channels Kv1.3 and KCa3.1. Expression of these channels does not vary with expression levels of maturation markers but varies between adherent and non-adherent NK cell subpopulations. Upon activation by mitogens or tumor cells, adherent NK (A-NK) cells preferentially up-regulate KCa3.1 and non-adherent (NA-NK) cells preferentially up-regulate Kv1.3. Consistent with this different phenotype, A-NK and NA-NK do not display the same sensitivity to the selective KCa3.1 blockers TRAM-34 and NS6180 and to the selective Kv1.3 blockers ShK-186 and PAP-1 in functional assays. Kv1.3 block inhibits the proliferation and degranulation of NA-NK cells with minimal effects on A-NK cells. In contrast, blocking KCa3.1 increases the degranulation and cytotoxicity of A-NK cells, but not of NA-NK cells. TRAM-34, however, does not affect their ability to form conjugates with target tumor cells, to migrate, or to express chemokine receptors. TRAM-34 and NS6180 also increase the proliferation of both A-NK and NA-NK cells. This results in a TRAM-34-induced increased ability of A-NK cells to reduce in vivo tumor growth. Taken together, our results suggest that targeting KCa3.1 on NK cells with selective blockers may be beneficial in cancer immunotherapy.

Highlights

Natural killer (NK) cells are large granular lymphocytes that participate in both innate and adaptive immune responses, including the killing of cancerous cells [1,2]
In keeping with the differences in potassium channel expression levels, CCR72 effector-memory T lymphocytes are preferentially sensitive to Kv1.3 blockers in proliferation, migration, and cytokine production assays whereas CCR7+ naıve and central-memory T cells depend on KCa3.1 for their function [4,5,6]
The Kv1.3 and KCa3.1 Phenotype of NK Cells Varies with. Their Adhesive Properties Following Incubation with rhIL-2 and rhIL-15 Since we have found that human peripheral blood NK cells are heterogeneous in terms of KCa3.1 and Kv1.3 expression, we separated the cells based on CD16 and CD56 expression levels and assessed their potassium channel phenotype

Summary

Introduction

Natural killer (NK) cells are large granular lymphocytes that participate in both innate and adaptive immune responses, including the killing of cancerous cells [1,2]. Two potassium channels have been targeted for selective modulation of the function of subpopulations of T and B lymphocytes These channels are the voltage-gated Kv1.3 (KCNA3) and the Ca2+-activated KCa3.1 channels (IKCa1, KCNN4) [3,4,5]. In keeping with the differences in potassium channel expression levels, CCR72 effector-memory T lymphocytes are preferentially sensitive to Kv1.3 blockers in proliferation, migration, and cytokine production assays whereas CCR7+ naıve and central-memory T cells depend on KCa3.1 for their function [4,5,6]. The difference in potassium channel expression is responsible for a differential sensitivity of the B cell subsets to blockers of Kv1.3 or KCa3.1 [7]

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Results

Conclusion