Abstract 4322: Tumor treating fields (TTFields) overcome anti-PD-1 resistance in a murine lung adenocarcinoma model

Abstract Tumor Treating Fields (TTFields) are low-intensity, intermediate-frequency alternating electric fields that disrupt mitosis and elicit immunogenic stress. Although TTFields are clinically approved for metastatic non-small-cell lung cancer (mNSCLC) with PD-1/PD-L1 inhibitors or docetaxel, their mechanistic synergy in anti-PD-1-resistant disease remains incompletely understood. We investigated the temporal transcriptomic and functional impact of TTFields using the murine 344SQR lung adenocarcinoma model, which is intrinsically resistant to PD-1 blockade.344SQR cells were exposed to TTFields (150 kHz, 1.62 V/cm) for 24-72 h using the inovitro™ system, and proliferation and clonogenic survival were quantified. RNA-seq with Gene Set Enrichment Analysis (GSEA) defined pathway modulation at 48 h and 72 h. In vivo, 129Sv/Ev mice bearing 344SQR tumors were treated with the inovivo™ system, anti-PD-1, or both treatments together.TTFields significantly inhibited 344SQR proliferation (∼60 % reduction at 72 h) and clonogenic survival in vitro. GSEA revealed dynamic, stage-specific transcriptional remodeling. At 48 h, TTFields downregulated mitotic-spindle, DNA-replication, and epithelial-mesenchymal-transition gene sets, indicating early mitotic arrest and replication stress. By 72 h, cells exhibited re-enrichment of G2M-checkpoint, E2F, MYC, and mitotic-spindle programs together with activation of peroxisomal and xenobiotic-metabolism pathways, consistent with sustained mitotic stress and oxidative-damage adaptation. In contrast, marked suppression of glycosyltransferase activity suggested impaired membrane and secretory functions, signifying progression toward metabolic exhaustion and immunogenic cell death.In vivo, TTFields monotherapy delayed tumor progression, while concurrent treatment with TTFields and anti-PD-1 produced significant tumor regression and extended median survival (32 days vs 20-21 days for control or monotherapies). Single-cell transcriptomics revealed that TTFields plus anti-PD-1 increased infiltration of CD8+ cytotoxic T cells and B cells while reducing regulatory T cells, shifting the tumor microenvironment toward an effector-dominant state.These findings demonstrate that TTFields trigger sequential mitotic stress and metabolic collapse, generating an immunogenic tumor phenotype that restores responsiveness to PD-1 blockade. Sustained tumor control requires PD-1 inhibition to capitalize on TTFields-induced immunogenic remodeling and prevent regrowth of metabolically adapted residual cells. Citation Format: Yun Hu, Fatemeh Maspourour, Qi Wang, Ailing Huang, Carola Leuschner, Jing Wang, James W. Welsh, . Tumor treating fields (TTFields) overcome anti-PD-1 resistance in a murine lung adenocarcinoma model abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4322.