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

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.