Abstract 4471: Reprogramming “cold” NF1 malignancies into “hot” tumors for immunotherapy

Abstract

Abstract Introduction: Neurofibromatosis Type 1 (NF1) results from mutations in the NF1 gene that inactivate the tumor suppressor, neurofibromin. This leads to hyperactive RAS signaling that predisposes NF1 patients to tumor development. Over time, some of these tumors can develop into malignant peripheral nerve sheath tumors (MPNST) which are currently incurable.Immune checkpoint blocking (ICB) programs a patient’s immune system to enhance tumor destruction. However, MPNSTs are cold tumors characterized by low immune cell presence in the tumor microenvironment. Interestingly, MPNSTs show checkpoint protein PD-L1 expression suggesting ICB as potential therapy for MPNST, given the ability to increase immune cell density in the tumor microenvironment. Activation of the intracellular receptor stimulator of interferon genes (STING) enhances antitumor immunity through the induction of pro-inflammatory cytokines and chemokines, including type I interferons. Cyclic GMP-AMP synthase (cGAS) is an enzyme that once bound to cytosolic DNA, synthesizes cyclic GMP-AMP (cGAMP), which activates STING to induce inflammatory cytokines and other immune mediators. Preclinical studies using mouse tumor models have assessed the efficacy of STING agonists that trigger the cGAS-STING-IFN axis, ultimately leading to augmented innate immunity and a T cell-rich tumor environment. Additionally, combining STING agonists with ICB has a synergistic effect in treating tumors. Therefore, we hypothesize that treatment with STING agonists would turn “cold” MPNSTs into “hot” tumors making them susceptible to targeting with ICB. Methods: We treated MPNST cell lines with synthetic STING agonist ADU-S100 for varying durations of 8, 18, 24, and 48 hours. At the end of the treatment, cells were harvested for qRT-PCR and immunoblot analysis. Results: We measured STING-IFN pathway activation through immunoblotting and observed that phosphorylation of STING effector proteins - a readout of STING activation – was increased followingby 8 hours after treatment. qRT-PCR analysis showed that STING target cytokine/chemokine gene expression was also upregulated by 8 hours after ADU-S100 treatment. Conclusions: Theise data demonstrates that ADU-S100 was able to activate the STING pathway in MPNST cell lines leading to proinflammatory cytokine/chemokine production. We will next test STING agonist in vivo use to determine whether ADU-S100 treatment inin mouse MPNST modelss of MPNST to is able to reprogram the tumor microenvironment into an immune inflamed one amenable to immunotherapy. Citation Format: Laasya Madana, Lu Q. Le, Nipunika Somatilaka, Renee McKay. Reprogramming “cold” NF1 malignancies into “hot” tumors for immunotherapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4471.