Integrative analysis reveals immune heterogeneity and immune regulatory genes in KRAS-mutant lung adenocarcinoma

Introduction: The tumor immune microenvironment (TIME) of KRAS-mutant lung adenocarcinoma (LUAD) is predominantly characterized by an immunosuppressive phenotype, which underpins its resistance to immunotherapy. This study aims to elucidate the role and molecular mechanism of phosphodiesterase 4D (PDE4D) in remodeling the TIME of KRAS-mutant LUAD.

Methods: Integrative bioinformatic analysis was performed using TCGA bulk RNA-seq and single-cell RNA-seq datasets to compare KRAS-mutant and wild-type LUAD, leading to the identification of PDE4D. Its clinical relevance was assessed via immunohistochemistry in patient cohorts. The immunomodulatory function of PDE4D was evaluated using CRISPR/Cas9-mediated knockout in KRAS-mutant LUAD cell lines (NCI-H2030, NCI-H2122) in both immunodeficient and humanized NSG mouse xenograft models. Mechanistic insights were obtained through PDE4D pulldown coupled with mass spectrometry to identify interacting partners.

Results: PDE4D was identified as a key immunomodulatory gene associated with an exhausted TIME phenotype in KRAS-mutant LUAD. High PDE4D expression significantly correlated with reduced CD8+ T cell infiltration and predicted poorer relapse-free survival and distant metastasis-free survival. Functional studies demonstrated that PDE4D knockout markedly suppressed tumor growth in both immunodeficient and humanized NSG mouse models. Proteomic analysis revealed that PDE4D interacts with several key epigenetic regulators.

Conclusion: This study uncovers a novel "PDE4D-epigenetic-immune exclusion" regulatory axis in KRAS-mutant LUAD. Our findings suggest that PDE4D promotes an immunosuppressive TIME, and its pharmacological inhibition could reprogram the tumor toward a "hot" phenotype, thereby overcoming immunotherapy resistance and suppressing metastasis.

To be updated shortly..