Altered immune landscape in aging lungs contributes to malignant evolution

Abstract Aging is a major risk factor in increased lung cancer incidence. While most research has focused on age-associated mutation accumulation to explain the late-life increase in cancer incidence, there are tissue environmental forces that both impede and promote cancer evolution. Just as organismal evolution is known to be driven by environmental changes, cellular (somatic) evolution in our bodies is similarly driven by changes in tissue environments. Environmental change promotes selection for new phenotypes that are adaptive to the new context. In our tissues, aging or insult-driven alterations in tissues drives selection for adaptive mutations, and some of these mutations can confer malignant phenotypes. Chronic, low-level inflammation has been associated with aging, termed inflammaging, yet how age-associated changes in lung tissue microenvironments contribute to increased lung cancer incidence has remained largely unknown. Since chronic inflammation has been shown to contribute to tumor development, we hypothesized that inflammaging contributes to increased oncogenic adaptation in the lung. Using either viral delivery of CRISPR constructs to mediate EML4-ALK translocations or ectopic expression of KRAS-G12D, we showed increased adenoma formation in old mice. Importantly, in the EML4-ALK model, we showed that the overexpression of alpha-1 antitrypsin (AAT) in old mice resulted in lower adenoma counts compared to their old wild type counterparts. Flow cytometric analysis of immune cells isolated from bronchoalveolar fluid of young and old mice showed an altered immune landscape, such as increased neutrophils, gamma delta T cells, and Foxp3+ regulatory T cells. Furthermore, analysis of the single-cell RNAseq data from Tabula Muris Consortium demonstrated increased exhaustion markers in the CD8+ T cells and regulatory T cells. Separately, Gene Set Enrichment Analysis (GSEA) of the differential gene expressions of lung epithelial cells isolated from young and old mice revealed enriched pathways related to immune activation and inflammatory response, and immune-suppression markers. Lastly, bulk RNA-seq from lungs of young, old, and old mice overexpressing AAT revealed increased immune cell exhaustion markers and that the overexpression of AAT partially reversed this increase. Finally, analysis of Genotype-Tissue Expression (GTEx) data comparing gene expressions in lungs of young and old humans similarly showed enriched pathways related to immune activation and increased T cell exhaustion markers in the elderly. In addition, using deconvolution methods CiberSort and xCell, we demonstrated altered innate and adaptive immune cell populations, for example, increased neutrophils and regulatory T cells, that are associated with advanced age, similar to aging mice. In conclusion, we showed that there is an exhausted immune microenvironment in aging lungs, that inflammation contributes to the increased tumor initiation, and that decreasing inflammation could decrease the lung tumor incidence by reactivating the immune system. Citation Format: Shi Biao Chia, Catherine Pham-Danis, Hannah Scarborough, Nathaniel Little, Etienne P. Danis, Andrew E. Goodspeed, Charles Dinarello, James DeGregori. Altered immune landscape in aging lungs contributes to malignant evolution [abstract]. In: Proceedings of the AACR Special Conference on the Evolutionary Dynamics in Carcinogenesis and Response to Therapy; 2022 Mar 14-17. Philadelphia (PA): AACR; Cancer Res 2022;82(10 Suppl):Abstract nr A026.