A novel PAK1/TCF1 regulatory axis promotes non-small cell lung cancer progression.

BACKGROUND: Non-small cell lung cancer (NSCLC) is the leading cause of cancer death, necessitating the identification of novel therapeutic targets. P21-activated kinases-1 (PAK1) plays a crucial role in oncogenesis, including NSCLC. Recent findings have elucidated T cell factor 1 (TCF1) as an anti-tumour factor, influencing T cell biology. However, the precise mechanism by which PAK1 promotes NSCLC progression via TCF1 regulation remains unclear. METHODS: We collected 23 pairs of NSCLC tissue samples and obtained NSCLC RNA sequencing data and corresponding clinicopathologic information from The Cancer Genome Atlas (TCGA). Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC) assessed PAK1 and TCF1 expression in NSCLC tissues and cells. Gain and loss-of-function experiments evaluated PAK1 and TCF1 effects on cell proliferation, invasion, migration, and apoptosis in vitro. Mechanistically, western blot (WB) and immunoprecipitation analysis evaluated the interaction between PAK1 and TCF1 in NSCLC. Finally, we assessed the clinical prognostic, disease progression, and immunotherapy response of PAK1 and TCF1 and their correlation with immune cell infiltration, immune checkpoint inhibitors (PD1, PDL1). RESULTS: PAK1 expression was elevated in NSCLC tissues and cells, while TCF1 was significantly downregulated. PAK1 expression showed a significant inverse correlation with TCF1 mRNA in NSCLC. Silencing PAK1 (using shRNAs) and inhibiting PAK1 with the small molecule IPA-3 suppressed NSCLC cell malignancy in a dose-dependent manner, upregulating TCF1 expression, and vice versa. TCF1 amplification with the small molecule (TWS119) inhibited NSCLC cell proliferation, migration, and invasion in a dose-dependent manner without affecting PAK1 expression. Immunoprecipitation analysis confirmed PAK1 and TCF1 interaction in NSCLC. Joint survival analysis indicated that high PAK1 and low TCF1 expression were associated with unfavourable survival in patients with NSCLC. Lastly, the TCF1 was significantly correlated with immune cell infiltration [CD8+ T cell, and tumor infiltrating lymphocytes (TILs)], immune checkpoint inhibitors (PD1, PDL1), and can accurately predict the immunotherapeutic response. CONCLUSION: This study demonstrates, for the first time, that PAK1 negatively regulates TCF1, contributing to NSCLC pathogenesis. The PAK1/TCF1 regulatory axis emerges as a critical determinant of carcinogenesis and a promising therapeutic target for NSCLC.