Irradiated CAF-like cells enhance nasopharyngeal carcinoma survival and radioresistance via PI3K/AKT/DNA-PKcs axis

Abstract Cancer-associated fibroblasts (CAFs) are key stromal cells in the tumor microenvironment (TME) and play critical roles in tumor progression and radioresistance. Radiotherapy kills malignant cells but also triggers stress in CAFs, which alters their phenotype and affects nearby tumor cells. However, how irradiated CAFs influence the survival and radioresistance of nasopharyngeal carcinoma (NPC) cells remains unclear. Human embryonic lung fibroblasts (WI-38) were induced into a CAF-like phenotype by transforming growth factor-β1 (TGF-β1) stimulation and then exposed to a single 6 Gy dose. HONE-1 cells were co-cultured with irradiated (irCAFs) or non-irradiated CAF-like cells (iCAFs). The CAF-like phenotype was characterized by reverse transcription quantitative polymerase chain reaction (RT-qPCR), Western blot (WB), and immunofluorescence (IF). Radiosensitivity was assessed using colony formation assays. CAF-like cell-secreted factors were quantified by enzyme-linked immunosorbent assay (ELISA). Flow cytometry was employed to analyze cell cycle distribution and apoptosis. The mechanisms underlying radioresistance were explored using RNA sequencing. In vivo experiments were conducted with a subcutaneous xenograft mouse model. IrCAFs developed a senescence-associated secretory phenotype (SASP) and significantly increased IL-8 secretion. IL-8 activated the PI3K/AKT signaling pathway in NPC cells, leading to DNA-PKcs phosphorylation and p27 degradation, thereby enhancing NPC cell survival and radioresistance in vitro and in vivo. Neutralization of IL-8 with MAB208 or inhibition of AKT with MK-2206 restored radiosensitivity and improved radiotherapy efficacy. IrCAFs promote NPC cell survival and radioresistance through the IL-8/PI3K/AKT/DNA-PKcs axis. Targeting AKT could enhance radiotherapy efficacy in NPC, offering a potential therapeutic strategy for overcoming radioresistance.