3.3 Lung cancer
Lung cancer is a highly malignant tumor of the bronchial mucosa or glands in the lung and displays rapid growth and early metastasis. Current SCS studies have revealed a central role played by cytotoxic and effector T cells, NK cells, and different functional macrophage (Mφ) subtypes in the immune microenvironmental heterogeneity of lung adenocarcinoma and lung squamous cell carcinoma [65]. Wu et al. [66] analyzed 42 tissue biopsies from patients with stage III/IV non-small cell lung cancer (NSCLC). Those analyses identified the rare cell types of follicular dendritic cells and T helper 17 cells in tumors, and explained the correlation between tumor heterogeneity and tumor-associated neutrophils. Li et al. [67] identified a cancer cell subtype that deviated from the normal differentiation trajectory and dominated the metastatic stage. The cells were obtained from 208,506 cells in normal tissue or from 44 patients with early-stage to metastatic cancer. The investigators found that the normal resident myeloid cell population was gradually replaced by monocyte-derived macrophages and dendritic cells, and was accompanied by T-cell failure. Overall, although there are still batch effects and difficulties with clinical implementation, SCS has provided new insights into the precision and accuracy of molecular cancer research on the tumor microenvironment and cell heterogeneity, and has significantly improved our understanding of cancer diagnostic stratification, biomarkers, precision therapy, and prognosis.