Dying cells initiate DLL4–Notch signaling to drive tumor repopulation after insufficient thermal ablation of papillary thyroid carcinoma

Although lacking high-quality clinical evidence, the use of thermal ablation for papillary thyroid carcinoma (PTC) is increasing. Emerging evidence suggests that thermal ablation may accelerate tumor progression in some patients, but the underlying biological mechanisms remain unclear. This study aims to explore the mechanisms of tumor repopulation following thermal ablation and identify possible intervention strategies. In vitro and in vivo models were employed to simulate tumor repopulation after thermal ablation and investigate mechanisms. Clinicopathological features of post-ablation surgical specimens were analyzed, and Xenium in situ spatial transcriptomics was conducted. Time-lapse imaging and RNA-seq explored how dying cells influence surviving cells. qPCR, WB, IHC, and flow cytometry validated molecular mechanisms, while enChIP-MS identified upstream regulators. Post-ablation PTC tissue showed significantly higher proliferative potential. Heat-induced dying cells promote surviving cell repopulation in a contact-dependent manner. Dying cells upregulated DLL4, activating Notch signaling in surviving cells and driving proliferation. Clinical specimens and Xenium in situ spatial transcriptomics revealed elevated Notch activity in tumor cells adjacent to the ablation bed. Inhibition of DLL4–Notch signaling attenuated the dying cell–induced proliferative advantage in vitro and in vivo. enChIP–MS showed HNRNPU enrichment at the DLL4 promoter after heat treatment. Mechanistically, heat treatment increased HNRNPU nuclear enrichment and binding at the DLL4 promoter, facilitating DLL4 transcription. Heat-induced dying cells promote tumor repopulation after insufficient thermal ablation in PTC through the DLL4–Notch pathway. With the expanding use of thermal ablation, understanding and mitigating its limitations is essential for clinical advancement.