HSF2BP modulates lung adenocarcinoma proliferation and immune microenvironment via BNC1/TGF-β/SMAD3 signaling pathway

The tumor microenvironment plays a critical role in the progression and metastasis of lung adenocarcinoma (LUAD), characterized by its immunosuppressive nature. Identifying the mechanisms that contribute to the remodeling of this environment is essential for developing therapeutic strategies. Heat shock factor 2-binding protein (HSF2BP) is implicated in tumor proliferation and immune evasion, but the mechanisms by which HSF2BP exerts these effects remain poorly understood. This study investigates the role of HSF2BP in modulating Basonuclin 1 (BNC1) expression and subsequent immune responses in LUAD. Matched tumor and adjacent normal tissue samples from 30 LUAD patients were collected between January 2023 and June 2024. Using lentiviral transduction, HSF2BP and BNC1 were overexpressed or knocked down in LUAD cell lines. Gene and protein expression were quantified by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting. We analyzed the immunological profile of LUAD tumors and assessed the interaction between HSF2BP and the BNC1/Transforming Growth Factor Beta (TGF-β)/SMAD3 signaling pathway through in vitro and in vivo experiments. Immune profiling included flow cytometry for Natural Killer (NK) cells and ELISA for cytokine analysis (IL-2, IL-4, IL-10, INF-γ, and TNF-α). In vivo studies involved subcutaneous tumorigenesis in BALB/c nude mice. Immunohistochemistry and co-immunoprecipitation were used to validate protein interactions and to assess remodeling of the tumor immune microenvironment. HSF2BP expression was markedly higher in LUAD tissues in matched adjacent normal tissues, whereas BNC1 expression was significantly reduced. Overexpression of HSF2BP in LUAD cells (H1299) enhanced proliferation, reduced the proportion of NK cells, decreased levels of IFN-γ, IL-2, and TNF-α, and increased levels of IL-4 and IL-10. Conversely, knockdown of HSF2BP in A549 cells reduced proliferation and restored the proportion of NK cells and levels of pro-inflammatory cytokines. In vivo studies using HSF2BP-overexpressing mice confirmed these findings, demonstrating increased tumor volumes and altered cytokine profiles. Molecular assays revealed that HSF2BP binds directly to BNC1, with the C-terminal hydrophobic domain being essential for this interaction, thereby modulations in TGF-β and SMAD3 signaling pathways. HSF2BP significantly promotes LUAD progression by modulating the BNC1/TGF-β/SMAD3 signaling axis and reshaping the tumor immune microenvironment. Targeting the HSF2BP-BNC1 interaction can provide novel therapeutic strategies for enhancing immune responses against LUAD.