Abstract 3855: Inhibition of MNK by eFT508 reprograms T-cell signaling to promote an antitumor immune response

Abstract

Mitogen-activated protein (MAP) kinase signaling cascades play a vital role in T-cell activation upon antigen recognition. MNK1 and MNK2 are important downstream effector kinases in the MAPK pathway that largely function in regulating the expression of important signaling molecules, including cytokines and immune checkpoint receptors. MNKs are primarily thought to regulate the expression of select mRNAs, predominantly via post-transcriptional mechanisms involving the phosphorylation of the eukaryotic translation initiation factor eIF4E as well as the RNA binding proteins hnRNPA1 and PSF. eFT508 is a potent and highly selective inhibitor of MNK1 and MNK2 that has been shown to promote antitumor immunity by decreasing the expression of immunosuppressive molecules, such as immune checkpoint receptors. In order to identify key T-cell components that are regulated by MNK phosphorylation and may mediate the effects of eFT508 treatment, we performed an unbiased phosphoproteomic analysis of T cells during the early stages of T-cell receptor-mediated stimulation with and without eFT508 treatment. Primary human T cells were pretreated with eFT508 for two hours prior to stimulation with αCD3/αCD28 for an additional 30 minutes. Protein samples were then prepared for multiplexed phosphoproteomic analysis by mass spectrometry. Consistent with previous proteomic studies using stimulated T cells, a number of phosphopeptides associated with T-cell receptor signaling, among other cellular activities, were detected. Moreover, treatment with eFT508 specifically blocked the phosphorylation of distinct phosphosites on select proteins. The phosphoproteins modulated by eFT508 treatment are involved in important T-cell signaling pathways, cell proliferation and differentiation programs, stress responses, and post-transcriptional and translational gene regulation. Furthermore, there was enrichment for specific sequences surrounding the phosphorylation site in eFT508-sensitive peptides, highlighting a potential mechanism mediating MNK target recognition. Confirmation of MNK-mediated phosphorylation of novel substrates is being conducted in vitro by biochemical analysis of direct phosphorylation of potential substrates by MNK1 or MNK2 and in cellular lysates treated with eFT508 by Western blot analysis using phosphosite-specific antibodies. These findings have significantly expanded our understanding of cell signaling through MNK1 and MNK2 and will help to illuminate potential regulatory programs through which inhibition of MNKs by eFT508 can modulate antitumor immunity. Citation Format: Craig R. Stumpf, Joan Chen, Vikas K. Goel, Gregory S. Parker, Gary G. Chiang, Peggy A. Thompson, Kevin R. Webster. Inhibition of MNK by eFT508 reprograms T-cell signaling to promote an antitumor immune response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3855.

Vinorelbine causes a neuropathic pain-like state in mice via STING and MNK1 signaling associated with type I interferon induction

“…It will be important to understand whether MNK inhibition will interfere with the anticancer activity of the chemotherapeutic, but this is unlikely since increased MNK activity and increased eIF4E phosphorylation are associated with many cancers 73 , 74 and MNK inhibitors are currently in clinical trials for cancer treatment. 75 It is crucial to emphasize that the combination of vinca alkaloids with potent pain management medications has the potential to substantially enhance the tolerability of cancer treatments, offering a prophylactic solution for chemotherapy-induced pain. Instead of advocating for reduced clinical use of vinca alkaloids, which may happen as cancer therapeutic development continues to progress, our work seeks to illustrate that, due to the multifaceted effects of these chemotherapeutic agents on signaling pathways, we can harness these mechanisms as therapeutic targets for pain, serving as proactive alternatives to mitigate chemotherapy-induced pain.…”

MNK inhibitor eFT508 (Tomivosertib) suppresses ectopic activity in human dorsal root ganglion neurons from dermatomes with radicular neuropathic pain

“…Another question emerging from this work is whether these effects of MNK are mediated by translation regulation via eIF4E or via other phosphorylation targets. First, the action of eFT508 at 25 nM in the experiments we describe is very likely specific for MNK because this drug has been tested against a broad variety of off-targets and has no known other activities at the concentration we used (Stumpf et al, 2018). While the kinetics of activity-dependent translation have not been measured in human nociceptors, detailed experiments have been done in rodent brain showing that changes in the synaptic proteome can be induced through translation regulation on the order of single minutes (Hafner et al, 2019;Latallo et al, 2019).…”

“…MNK1/2 are downstream targets of ERK and p38 and both genetic and pharmacological inhibition of MNK signaling reduces evoked and spontaneous aspects of neuropathic and other forms of pain in animal models (Moy et al, 2017;Megat et al, 2019;Mihail et al, 2019;Barragan-Iglesias et al, 2020;Shiers et al, 2020;Lackovic et al, 2023). The MNK inhibitor eFT508 has recently been named Tomivosertib because this drug has entered late-stage clinical trials for oncology indications (Stumpf et al, 2018). The specificity of this molecule, as well as its demonstrated safety profile in humans makes it an ideal candidate for testing the hypothesis that MNK signaling plays a key role in generating SA in human nociceptors.…”

Vinorelbine causes a neuropathic pain-like state in mice via STING and MNK1 signaling associated with type I interferon induction

“…Our findings support the idea that MNK represents a promising mechanistic target for pharmacological relief or prevention of chemotherapy-induced pain. It will be important to understand whether MNK inhibition will interfere with the anti-cancer activity of the chemotherapeutic, but this is unlikely since increased MNK activity and increased eIF4E phosphorylation is associated with many cancers (69, 70) and MNK inhibitors are currently in clinical trials for cancer treatment (71).…”