Characterizing dynamic tumor–immune interactions in lung adenocarcinoma through orthotopic allograft modeling

The major clinical challenge in lung cancer immunotherapy is drug resistance. Therefore, establishing efficient orthotopic lung cancer mouse models to explore the mechanisms of drug immunotherapy resistance is highly important. In this study, we generated multiple fluorescently labeled lung adenocarcinoma cell lines from a genetically engineered KPZ mice model. Orthotopic transplantation of the primary 1F3 cell line induced a strong immune response, causing many small tumors to disappear, but some tumors evaded the immune attack and eventually formed large tumors. Tumor microenvironment analysis demonstrated that M2 macrophages play key roles in the immune response. Further mechanistic studies revealed that the chemokine CCL7 promoted the infiltration of M2 macrophages to facilitate immune escape, thereby promoting tumor growth in the orthotopic mouse model. Moreover, CCL7 levels were elevated in human lung cancer biopsies and positively correlated with M2 macrophage infiltration, and high CCL7 levels predicted advanced pathological stage and poor survival in lung cancer patients. Overall, we established a visualized and orthotopic mouse model with fluorescently labeled cells to better dissect the tumor microenvironment of lung cancer and define the critical role of CCL7 in promoting M2 macrophage polarization and tumorigenesis, providing new preclinical tools and potential targets for lung cancer immunotherapy.