Hypoxia-induced tumor cell-intrinsic PLAU activation drives immunotherapy resistance in collagenic lung adenocarcinoma

Abstract

Background

Hypoxia, as one of the hallmarks in the progression of solid tumors, has been established as critically important for tumor adaptive survival; however, its role in mediating tumor microenvironment remodeling in advanced lung adenocarcinoma (LUAD) remains incompletely defined.

Methods

Bioinformatics methods were conducted to establish a “hypoxia gene module” and perform molecular subtyping of advanced LUAD patients.Western blotting and immunohistochemistry analyses were performed to elucidate the role of PLAU-PLAUR (also known as uPA-uPAR) signaling activation in hypoxia-associated “Collagenic” LUAD development. Primary pulmonary fibroblasts were isolated, and a co-culture system was established for further investigation. QRT-PCR, Western blotting, and ELISA assays were employed to assess PLAU-PLAUR pathway involvement in CAFs activation. Additionally, CUT&RUN, mass spectrometry, immunofluorescence, and co-immunoprecipitation experiments were conducted to explore the molecular mechanisms of HIF1A-induced PLAU upregulation. In vivo studies were undertaken to examine PLAU-PLAUR activation's impact on the formation of a collagen-rich tumor microenvironment.

Results

We observed that advanced LUAD patients with high hypoxia exhibited higher fibrosis and increased infiltration of immunosuppressive cells in their microenvironment. Screening intercellular communication signals revealed abnormal activation of the PLAU-PLAUR pathway between tumor cells and fibroblasts in hypoxia-induced “Collagenic” LUAD. In vitro experiments confirmed that hypoxia upregulates PLAU in tumor cells, promoting CAFs activation. Furthermore, hypoxia-inducible factor 1α(HIF1A) recruits the mitophagy protein NIX for a non-canonical role: under hypoxia, NIX translocates to the nucleus, interacts with the PLAU transcription factor YY1, and enhances its binding to the PLAU promoter. We also identified that PLAU activates Hippo-YAP signaling upon binding to PLAUR on lung fibroblasts. In vitro studies demonstrated that Upamostat significantly attenuated fibroblast activation at tumor borders, enhanced CD8⁺T cell infiltration, and shifted macrophages from immunosuppressive to immunogenic states.

Conclusions

Activation of the PLAU-PLAUR pathway is essential for the progression of hypoxia-associated LUAD exhibiting a collagenous phenotype. Blocking the pathway provides a new research perspective for the development of immunotherapy for LUAD.