Smoker and non-smoker lung adenocarcinoma is characterized by distinct tumor immune microenvironments.

Tobacco smoking causes DNA damages in epithelial cells and immune dysfunction in the lung, which collectively contribute to lung carcinogenesis and progression. However, potential mechanisms by which tumor-infiltrating immune cells contribute to lung cancer survival and their differential contributions in ever-smokers and never-smokers are not well studied. Here, we performed integrative analysis of 11 lung cancer gene-expression datasets, including 1,111 lung adenocarcinomas and 200 adjacent normal lung samples. Distinct pathways were altered in lung carcinogenesis in ever-smokers and never-smokers. Never-smoker patients had a better outcome than ever-smoker patients. We characterized compositional patterns of 21 types of immune cells in lung adenocarcinomas and revealed the complex association between immune cell composition and clinical outcomes. Interestingly, we found two subsets of immune cells, mast cells and CD4 memory T cells, which had completely opposite associations with outcomes in resting and activated status. We further discovered that several chemokines and their associated receptors (e.g., CXCL11-CX3CR1 axis) were selectively altered in lung tumors in response to cigarette smoking and their abundances showed stronger correlation with fractions of these immune subsets in ever-smokers than never-smokers. The status switched from the resting to activated forms in mast cells and CD4 memory T cells might manifest some important processes induced by cigarette smoking during tumor development and progression. Our findings suggested that aberrant activation of mast cells and CD4+ memory T cells plays crucial roles in cigarette smoking-induced immune dysfunction in the lung, which contributes to tumor development and progression.