Homeobox D9 Promotes Malignant Progression of Non-Small Cell Lung Cancer Through Negatively Regulating Kallikrein Related Peptidase 9

Abstract

We investigated the association between HOXD9 expression and prognosis in non-small cell lung cancer (NSCLC) and explored its underlying mechanisms in tumor progression. HOXD9 expression was examined in 42 pairs of NSCLC tissue samples using qRT-PCR, and its effects were evaluated in NSCLC cell lines through lentiviral vector transfection, assessing cell growth and migration using CCK-8 and Transwell assays. Bioinformatics analysis identified KLK9 as a target gene of HOXD9, and their interaction was investigated in vitro and in vivo. HOXD9 mRNA expression was significantly higher in NSCLC tissues compared to adjacent tissues, positively correlating with metastasis incidence and poor prognosis. HOXD9 knockdown reduced NSCLC cell migration and proliferation, while overexpression had the opposite effect. Luciferase assays confirmed HOXD9′s binding to KLK9, leading to negative regulation of KLK9 expression. Knockdown of KLK9 reversed the inhibitory effect of HOXD9 on NSCLC cell migration and proliferation, while co-overexpression of KLK9 and HOXD9 had the opposite effect. Our findings demonstrate the close association of high HOXD9 expression in NSCLC tissues with metastasis incidence and poor prognosis. HOXD9 likely exerts its biological function in NSCLC by negatively regulating KLK9. These results provide valuable insights into the molecular mechanisms driving NSCLC progression, highlighting HOXD9 as a potential prognostic biomarker and therapeutic target.