Cancer-Associated Fibroblasts Drive Papillary Thyroid Cancer Progression through ROS/NF-κB/IL-6 Signaling in Hypoxic Microenvironment

Cancer-associated fibroblasts (CAFs) are key components of the tumour microenvironment (TME) in papillary thyroid carcinoma (PTC) and play a critical role in disease progression. We previously reported that interleukin-6 (IL-6) promotes PTC progression through activation of MAPK signalling. However, whether CAFs serve as a major source of IL-6 and the underlying regulatory mechanisms remain incompletely understood. By integrating single-cell RNA-seq data from PTC patients, we identified fibroblasts as the predominant cellular source of IL-6, with IL-6 expression positively correlated with the CAF marker ACTA2. Primary CAFs isolated from PTC tissues exhibited enhanced proliferation, migration, glycolysis and IL-6 secretion compared with normal fibroblasts (NFs), and these phenotypes were further potentiated by hypoxia. Mechanistically, hypoxia induced reactive oxygen species (ROS) accumulation in CAFs, which activated NF-κB signalling to drive IL-6 production. Blocking NF-κB with JSH-23 or scavenging ROS with NAC or MitoQ abrogated hypoxia-induced IL-6 expression. In non-contact co-cultures, CAF-derived IL-6 promoted PTC cell proliferation and MAPK pathway activation under hypoxia, whereas IL-6 knockdown reversed these effects. In vivo, co-injection of CAFs with PTC cells enhanced tumour growth, which was significantly suppressed by the IL-6 receptor blocker tocilizumab. Collectively, these findings reveal that hypoxia activates a ROS/NF-κB/IL-6 axis in CAFs, which in turn drives PTC progression through paracrine IL-6 signalling. Targeting this pathway may represent a potential therapeutic strategy for aggressive PTC.