Single‐cell RNA sequencing reveals the multi‐cellular ecosystem in different radiological components of pulmonary part‐solid nodules

BACKGROUND: Early‐stage lung adenocarcinoma that radiologically manifests as part‐solid nodules, consisting of both ground‐glass and solid components, has distinctive growth patterns and prognosis. The characteristics of the tumour microenvironment and transcriptional features of the malignant cells of different radiological phenotypes remain poorly understood. METHODS: Twelve treatment‐naive patients with radiological part‐solid nodules were enrolled. After frozen pathology was confirmed as lung adenocarcinoma, two regions (ground‐glass and solid) from each of the 12 part‐solid nodules and 5 normal lung tissues from 5 of the12 patients were subjected to single‐cell sequencing by 10x Genomics. We used Seurat v3.1.5 for data integration and analysis. RESULTS: We comprehensively dissected the multicellular ecosystem of the ground‐glass and solid components of part‐solid nodules at the single‐cell resolution. In tumours, these components had comparable proportions of malignant cells. However, the angiogenesis, epithelial‐to‐mesenchymal transition, KRAS, p53, and cell‐cycle signalling pathways were significantly up‐regulated in malignant cells within solid components compared to those within ground‐glass components. For the tumour microenvironment, the relative abundance of myeloid and NK cells tended to be higher in solid components than in ground‐glass components. Slight subtype composition differences existed between the ground‐glass and solid components. The T/NK cell subsets’ cytotoxic function and the macrophages’ pro‐inflammation function were suppressed in solid components. Moreover, pericytes in solid components had a stronger communication related to angiogenesis promotion with endothelial cells and tumour cells. CONCLUSION: The cellular landscape of ground‐glass components is significantly different from that of normal tissue and similar to that of solid components. However, transcriptional differences exist in the vital signalling pathways of malignant and immune cells within these components.