Abstract 587: Tumor treating fields induce the integrated stress response, alter the transcriptional signatures of cellular metabolism, and modulate immune-related cytokines dependent and independent of p53
Authors: Srinivasan Praveen R. , George Andrew , Chou Charissa , Pinho-Schwermann Maximilian , Ghandali Maryam , Tajiknia Vida , Porat Yaara , Giladi Moshe , Armstead Andrea , Uzun Alper , Wong Eric T. , El-Deiry Wafik S. 
Published: March 2024

Abstract
Tumor treating fields (TTFields) are an FDA-approved therapy for the treatment of glioblastoma and pleural mesothelioma. TTFields employ alternating electric fields delivered by cutaneous transducer arrays to induce cytostatic and cytotoxic effects on solid tumors. Additionally, recent studies suggest that TTFields may enhance anti-tumor immunity. We performed RNA-seq and multiplexed cytokine profiling in HCT116 wild-type and HCT116 p53-/- human colorectal cancer cells to elucidate TTFields’ effects on the transcriptome and secretome. TTFields lead to profound changes in the transcriptome related to metabolism, including downregulation of transcripts coding for multiple enzymes involved in the Krebs cycle, fatty acid synthesis, and glycolysis. Furthermore, though only HCT116 p53-wild type cells strongly induced the p53 pathway, both cell types’ transcriptomes showed strong downregulation of cell cycle progression. Our cytokine data showed that key tumor-promoting cytokine IL-8 was downregulated independently of p53. We identified upregulation of immunomodulatory cytokines MIF and MICB independently of p53. While MICB promotes NK cell activation, MIF drives tumor progression. Therefore, MICB may be one way in which TTFields enhance anti-tumor immunity; targeting MIF during TTFields treatment may lead to synergy by abolishing its pro-tumor effects. We also identified a p53-dependent decrease in the TRAIL decoy receptor DcR3, which normally protects tumor cells from TRAIL-induced apoptosis. Further mechanistic work showed that TTFields induce EIF2-alpha phosphorylation, the central protein involved in activating the integrated stress response (ISR), across multiple cancer types, leading to suppression of global protein translation. TTFields treatment also resulted in increased expression of surface calreticulin, an endoplasmic reticulum stress marker, which activates the ISR. Future mechanistic work will explore the impact of identified cytokines and the ISR on anti-tumor immunity both in vitro and in vivo, as well as metabolic alterations induced by TTFields. This work identifies potential biomarkers and rationales for therapeutic combinations exploiting TTFields-induced molecular alterations.
Citation Format: Praveen R. Srinivasan, Andrew George, Charissa Chou, Maximilian Pinho-Schwermann, Maryam Ghandali, Vida Tajiknia, Yaara Porat, Moshe Giladi, Andrea Armstead, Alper Uzun, Eric T. Wong, Wafik S. El-Deiry. Tumor treating fields induce the integrated stress response, alter the transcriptional signatures of cellular metabolism, and modulate immune-related cytokines dependent and independent of p53 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 587.