TFAP2A Transcriptionally Activates CST2 to Promote the Malignant Progression of Non‐Small Cell Lung Cancer

ABSTRACT Non‐small cell lung cancer (NSCLC) remains a leading cause of cancer‐related mortality worldwide. Accumulating evidence suggests that dysregulation of cystatin SA (CST2) plays a pivotal role in tumor progression. However, the underlying mechanisms and clinical significance of CST2 in NSCLC remain unexplored, highlighting the need for a comprehensive investigation to identify potential therapeutic targets. The study recruited 69 NSCLC patients and purchased NSCLC cell lines including A549, PC‐9, and H1299 as well as human bronchial epithelial cells (16HBE) for the study. The mRNA levels of CST2 and transcription factor AP‐2 alpha (TFAP2A) were quantified using quantitative reverse transcription polymerase chain reaction, while their protein expression was assessed by western blotting or immunohistochemistry assay. Cell proliferation, apoptosis, migration, and invasion were analyzed using the 5‐Ethynyl‐2'‐deoxyuridine assay, flow cytometry, wound‐healing assay, transwell migration and invasion assays, respectively. Reactive oxygen species (ROS) levels and Fe 2+ concentrations were measured by flow cytometry and colorimetric assay, respectively. The chromatin immunoprecipitation (ChIP)assay and dual‐luciferase reporter assay were employed to elucidate the relationship between TFAP2A and CST2. A xenograft mouse model assay was conducted to evaluate the effects of TFAP2A and CST2 on the malignant progression of H1299 and A549 cells. The results showed that CST2 expression was found to be upregulated in NSCLC tissues and cells. CST2 promoted the proliferation, migration and invasion of H1299 and A549 cells, while inhibiting apoptosis, oxidative stress, and ferroptosis. TFAP2A transcriptionally activated CST2 in both H1299 and A549 cells, leading to the promotion in tumor progression in vitro. Similarly, TFAP2A enhanced the malignant progression of NSCLC cells in vivo by upregulating CST2 expression. Therefore, TFAP2A transcriptionally activated CST2, contributing to the malignant progression of NSCLC. These findings underscored the potential clinical significance of targeting the TFAP2A/CST2 axis as a novel therapeutic strategy for the treatment of NSCLC.