Modulation of the local angiotensin II: Augmentation of ferroptosis and radiosensitivity in nasopharyngeal carcinoma via the HIF-1α-HILPDA axis

Purpose: Radiotherapy presents a curative approach for nasopharyngeal carcinoma (NPC); however, the cellular radiosensitivity heterogeneity limits its efficacy. Thus, investigating the specific mechanisms of radioresistance in NPC is crucial for identifying and employing effective radiosensitizing agents to enhance treatment success.

Methods and materials: Radioresistant NPC cell lines HONE1-RR and SUNE1-RR were established. Quantitative reverse transcription-PCR (qRT-PCR), western blot, and enzyme-linked immuno sorbent assay (ELISA) were employed to detect the activation of the angiotensinogen (AGT) and local angiotensin II (Ang II). Transmission electron microscopy, ferrous ion detection, and lipid oxidation levels were utilized to detect radiation-induced ferroptosis in NPC. Bioinformatics analysis, along with qRT-PCR, western blotting, co-immunoprecipitation, and dual-luciferase assays were employed to explore downstream mechanisms. Colony formation assay, Cell Counting Kit-8 (CCK-8) assay, and a nude mouse xenograft model were utilized to assess NPC radiosensitivity. The expression of AGT, hypoxia-inducible factor-1 alpha (HIF-1α), hypoxia-inducible lipid droplet-associated protein (HILPDA), and glutathione peroxidase 4 (GPX4) in NPC tissues was detected through immunohistochemistry.

Results: Activation of local Ang II was revealed to play a critical role in driving radioresistance in NPC cells modulating ferroptosis. This local Ang II established a positive feedback loop with HIF-1α through two parallel pathways; Ang II stabilizes HIF-1α by activating the MAPK pathway, and AGT directly binds HIF-1α to prevent its degradation. This AGT-HIF-1α loop regulated NPC cell ferroptosis via transcriptional regulation of HILPDA expression. Moreover, the co-administration of Ang II receptor antagonist (ARB) and ferroptosis inducers markedly increased NPC radiosensitivity.Additionally, the expression of AGT, HIF-1α, and HILPDA was closely correlated with the intensity of ferroptosis, radiosensitivity, and prognosis in NPC.

Conclusions: Our findings suggest that the AGT-HIF-1α-HILPDA pathway promotes radioresistance in NPC by enhancing lipid droplet accumulation, thereby suppressing ferroptosis. Targeting local Ang II alongside ferroptosis induction offers a promising strategy to improve radiosensitivity in NPC.