Tumor-Associated Macrophage-Derived TGF-β1 Activates GLI2 via the Smad2/3 Signaling Pathway to Affect Cisplatin Resistance in Lung Adenocarcinoma

Abstract

Background Transforming growth factor-β1 (TGF-β1) is an immunosuppressive cytokine that is highly expressed in the tumor microenvironment (TME) of lung adenocarcinoma (LUAD). TGF-β1 plays important roles in regulating tumor metastasis and chemotherapy resistance. However, the specific molecular mechanisms by which TGF-β1 regulates cisplatin resistance in the TAM of LUAD remain unclear. Materials and methods THP-1 induced macrophages were co-cultured with A549 and H1975 cells, and subsequently transfected with silencing TGF-β1 (siTGF-β1), GLI2 (siGLI2), a GLI2 overexpression plasmid, and their negative controls. Cellular activity was measured by CCK-8 and colony formation assays. Cell apoptosis was evaluated by flow cytometry and TUNEL staining. Transwell assays were performed to assess cell migration and invasion capabilities. The levels of Smad2/3, GLI2, cyclin D, and cyclin E expression were evaluated by qPCR, western blotting, and immunofluorescence methods. TGF-β1 levels were determined by ELISA. Results Macrophages suppressed the apoptosis and promoted the migration and invasion of LUAD cells. TAM siTGF-β1 downregulated the Smad2/3 signaling pathways and GLI2 expression, deceased cell proliferation, and promoted apoptosis. SiGLI2 increased apoptosis and decreased the proliferation of LUAD cell lines. GLI2 decreased cisplatin resistance in LUAD cells. Conclusion High expression of TGF-β1 in the TAM positively activates GLI2 expression via the Smad2/3 pathway, which subsequently regulates cyclin D and cyclin E expression, and promotes the cisplatin resistance of LUAD.