A Study on Immune Cell Infiltration in Lung Adenocarcinoma

Background: As a vital part of the tumor environment, immune cells affect the progression of tumors, and their composition and role vary in different types of tumors and influence prognosis. These immune cells have the potential to be beneficially targeted for immunotherapy, or, conversely, they may react negatively, even leading to drug resistance. For these reasons, probing into the composition and possible effects of immune cells in lung cancer is conducive to discovering valuable therapeutic targets. Materials and Methods: The lung adenocarcinoma gene expression data were downloaded from the TCGA database (https://cancergenome.nih.gov/; https://portal.gdc.cancer.gov/), and the lung adenocarcinoma gene expression matrix was converted into an immune cell-matrix using CIBERSORT software (https://cibersort.stanford.edu/), followed by an analysis of immune cells in lung adenocarcinoma tissues. Results: The results showed that among all immune cells in lung adenocarcinoma tissues, macrophages (Mφ) had the highest number, followed by T cells. The number of plasma cells in lung adenocarcinoma tissues was higher than in adjacent normal tissues. Compared with those in adjacent normal tissues, the number of resting memory clusters of differentiation 4 (CD4)⁺ T cells was lower, whereas active memory CD4⁺ T cells were higher in lung adenocarcinoma tissues. In addition, the number of CD8⁺ T cells was negatively related to that of resting memory CD4⁺ T cells, with a correlation coefficient of -0.44, whereas it showed a positive association with the number of active memory CD4⁺ T cells, with a correlation coefficient of 0.47. It was found that among various immune cells infiltrating lung adenocarcinoma tissues, unstimulated Mφ (M0), alternatively activated Mφ (M2), and resting memory CD4⁺ T cells accounted for the largest proportions. However, these three types of immune cells were found to be lower in lung adenocarcinoma tissues than in adjacent normal tissues. Conclusion: Immune cells infiltrating lung adenocarcinoma tissues are complex, which affect the development and progression of the tumor and may also be a significant cause of drug resistance. Studying the changes in immune cell infiltration during the development of specific types of tumors contributes to disease progression interpretation, prognosis assessment, and potential solutions to the existing drug resistance issue. In this paper, the status of immune cells in lung adenocarcinoma tissues was preliminarily discussed based on the database mining, but more experimental studies and in-depth discussions are needed in the future.