Nucleoside Diphosphate Kinase-3 (NME3) Enhances TLR5-Induced NFκB Activation.

Kelly Flentie,Jayne Marasa,David Piwnica-Worms,Caleb Gonzalez,Yue Wang,Hongtu Zhu,Brandon Kocher

doi:10.1158/1541-7786.mcr-17-0603

Abstract

Bacterial flagellin is a potent activator of NFκB signaling, inflammation, and host innate immunity, and recent data indicate that flagellin represents a novel antitumor ligand acting through toll-like receptor 5 (TLR5) and the NFκB pathway to induce host immunity and aid in the clearance of tumor xenografts. To identify innate signaling components of TLR5 responsible for these antitumor effects, a loss-of-function high-throughput screen was employed utilizing carcinoma cells expressing a dynamic NFκB bioluminescent reporter stimulated by Salmonella typhimurium expressing flagellin. A live cell screen of a siRNA library targeting 691 known and predicted human kinases to identify novel tumor cell modulators of TLR5-induced NFκB activation uncovered several interesting positive and negative candidate regulators not previously recognized, including nucleoside diphosphate kinase 3 (NME3), characterized as an enhancer of signaling responses to flagellin. Targeted knockdown and overexpression assays confirmed the regulatory contribution of NME3 to TLR5-mediated NFκB signaling, mechanistically downstream of MyD88. Furthermore, Kaplan-Meier survival analysis showed that NME3 expression correlated highly with TLR5 expression in breast, lung, ovarian, and gastric cancers, and furthermore, high-level expression of NME3 increased overall survival for patients with breast, lung, and ovarian cancer, but the opposite in gastric cancer. Together, these data identify a previously unrecognized proinflammatory role for NME3 in signaling downstream of TLR5 that may potentiate cancer immunotherapies.Implications: Proinflammatory signaling mediated by innate immunity engagement of flagellin-activated TLR5 in tumor cells results in antitumor effects through NME3 kinase, a positive downstream regulator of flagellin-mediated NFκB signaling, enhancing survival for several human cancers. Mol Cancer Res; 16(6); 986-99. ©2018 AACR.

Highlights

Harnessing host immunity constitutes a promising cancer therapeutic strategy [1,2,3], and agonists of Toll-like receptors (TLR) have been actively pursued for their antitumor potential, either as monotherapy or as adjuvants to vaccination or other therapeutic modalities [4,5,6]
Expression of this kinase, which we demonstrate to be required for maximal toll-like receptor 5 (TLR5) signaling by bacterial flagellin, is correlated with enhanced survival rates in lung and breast cancer patients
Salmonella engagement of TLR5 and activation of NFkB serves primarily to alert the host of invading pathogens, which is accomplished by activating specific signaling pathways, release of cytokines and recruitment of host immune cells to the local microenvironment

Summary

Introduction

Harnessing host immunity constitutes a promising cancer therapeutic strategy [1,2,3], and agonists of Toll-like receptors (TLR) have been actively pursued for their antitumor potential, either as monotherapy or as adjuvants to vaccination or other therapeutic modalities [4,5,6]. In this context, Salmonella typhimurium, a common flagellated facultative intracellular bacterial pathogen, has been identified as a potential tumor therapeutic, capable of inducing tumor regression [7,8,9,10,11,12,13].

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