By integrating single-cell RNA sequencing and bulk RNA sequencing, plasma cells signature and tertiary lymphoid structures were verified to contribute to outcome in lung adenocarcinoma.

Abstract

Background: Tertiary lymphoid structures (TLS), consisting of T cell zones, B cell follicles, and germinal centers (GCs), are ectopic lymphoid tissue that form within non-lymphoid tissue. It has recently become a focus of attention. The TLS serve as an effective site for generating an anti-tumor inflammatory response by infiltrating immune cells, especially plasma cells. Thus, we aimed to explore the role of both TLS and plasma cells in influencing the prognosis of lung adenocarcinoma (LUAD).

Methods: Single-cell RNA sequencing (scRNA-seq) data were obtained from the Gene Expression Omnibus (GEO) database, and bulk RNA-seq data and clinical information were downloaded from The Cancer Genome Atlas (TCGA) database. Seurat R package was used to process scRNA-seq data and identify clusters by the marker genes with Kaplan-Meier (KM) curves plotted to predict the prognosis. Finally, hematoxylin and eosin (H&E) staining and multiplex immunofluorescence analysis were conducted to corroborate our suspicions.

Results: Seven clusters were identified in LUAD based on scRNA-seq data, with the number of B cells differing significantly between early and advanced cohorts. The plasma cells were also increased in advanced lung cancer (LC) and the number of TLS was significantly related to tumor stage. Then, via KM method, we confirmed that both plasma cells and TLS were associated with patient outcomes. Finally, H&E staining and multiplex immunofluorescence analysis verified the correlation between the two.

Conclusions: Plasma cells and TLS can effectively predict the prognosis of LUAD. In the tumor microenvironment (TME) of advanced tumors, plasma cells might be in a state of functional exhaustion. Comprehensive characterization of TLS and corresponding B‑cell pathways may help to activate the function of plasma cells and provide new strategies for cancer treatment.