Abstract Background: Loss of tumor-specific MHC class I (tsMHC-I) is a recurrent feature of lung adenocarcinoma (LUAD) progression and is associated with immune escape and poor outcomes. However, how tsMHC-I downregulation shapes tumor evolution and remodels the immune microenvironment remains unclear. Methods: We integrated single-cell RNA sequencing, spatial transcriptomics, and multiplex imaging from human LUAD samples spanning precancerous lesions to advanced tumors, together with longitudinal genetically engineered mouse models (GEMMs). Functional assays—including neutrophil co-culture, assessment of neutrophil extracellular traps (NETs), and in vivo tumor studies—were performed to define mechanistic consequences of tsMHC-I loss. Results: Progressive tsMHC-I downregulation was observed across LUAD evolution and validated in GEMMs. Single-cell trajectory analysis showed that reduced tsMHC-I is linked to loss of alveolar type II identity, increased chromosomal instability, heightened tumor plasticity, and acquisition of epithelial-mesenchymal transition (EMT) programs. Functionally, tsMHC-ILow malignant cells displayed increased invasiveness and metastatic capacity. Spatial and immunophenotypic profiling revealed that tsMHC-I downregulation reshapes the tumor microenvironment toward a neutrophil-enriched, cytotoxic cell-excluded niche. tsMHC-ILow regions exhibited dense tumor-associated neutrophil aggregates and depletion of CD8+ T cells, NK cells, and other effector populations. Mechanistic studies showed that tsMHC-ILow malignant cells induce robust NET formation. In vitro assays identified Annexin A2, a tumor-secreted protein, as a key driver of NET induction. Annexin A2 expression and secretion were consistently elevated in tsMHC-ILow cells across human and mouse models, and Anxa2 knockdown markedly reduced NET formation. Targeting NETs in vivo with DNase I selectively suppressed growth and metastatic spread of tsMHC-ILow tumors, restored cytotoxic immune infiltration, and reversed the immune-excluded phenotype. In tsMHC-I heterogeneous tumors, combining NET inhibition with anti-PD-1 enhanced tumor control and survival. Conclusions: Our integrated analyses reveal that tsMHC-I downregulation drives neutrophil recruitment and NET formation through Annexin A2 secretion, creating an immunosuppressive barrier that promotes LUAD progression and limits immunotherapy response. These findings identify a previously unrecognized tsMHC-I-NET axis as a therapeutic vulnerability in LUAD. Citation Format: Yanhua Tian, Jian-Rong Li, Bo Zhu, Jared Fradette, Hong Chen, Zhubo Wei, Jie Ye, Shao-Wei Lu, Andrew Y. Liu, Samrat T. Kundu, Haoyi Wu, Shucheng Miao, Xiuning Le, Linghua Wang, Jia Wu, Alexandre Reuben, John V. Heymach, Andy Futreal, Honami Naora, Chao Cheng, Don L. Gibbons, Jianjun Zhang. Spatiotemporal analysis reveals tsMHC-I downregulation-induced neutrophil extracellular traps as a driver of lung adenocarcinoma neoplastic evolution abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 200.
Tian et al. (Fri,) studied this question.