Single‐cell RNA sequencing analysis reveals transcriptional heterogeneity of multiple primary lung cancer

INTRODUCTION: With the advancements in early diagnosis, more and more patients with multiple primary lung cancer (MPLC) have been identified. However, the progression of MPLC involves complex changes in cell composition and metabolic function, which remains largely controversial. OBJECTIVE: Our study aims to comprehensively reveal the cellular characteristics and inter‐cellular connections of MPLC. METHODS: We performed scRNA‐seq from 23 samples of six MPLC patients, combined with bulk whole‐exome sequencing. We performed trajectory analysis to investigate the transition of different cell types during the development of MPLC. RESULTS: A total of 1 67 397 cells were sequenced derived from tumour and adjacent tissues of MPLC patients, and tumour, normal, immune and stromal cells were identified. Two states of epithelial cells were identified, which were associated with immune response and cell death, respectively. Furthermore, both CD8(+) naïve and memory T cells participated in the differentiation of CD8(+) T cells. The terminal states of CD8(+) T cells were exhausted T cells and cytotoxic T cells, which positively regulated cell death and were implicated in the regulation of cytokine production, respectively. Two main subpopulations of B cells with distinct functions were identified, which participate in the regulation of the immune response and antigen presentation, respectively. In addition, we found a specific type of endothelial cells that were abundant in tumour samples, with an increasing trend from normal to tumour samples. CONCLUSIONS: Our study showed the comprehensive landscape of different cells of MPLC, which might reveal the key cellular mechanisms and, therefore, may provide new insights into the early diagnosis and treatment of MPLC.