Single-cell RNA sequencing reveals a pro-invasive cancer-associated fibroblast subgroup associated with poor clinical outcomes in patients with gastric cancer

Abstract

Background:The protumor activities of cancer-associated fibroblasts (CAFs) suggest that they are potential therapeutic targets for the treatment of cancer. The mechanism of CAF heterogeneity in gastric cancer (GC) remains unclear and has slowed translational advances in targeting CAFs. Therefore, a comprehensive understanding of the classification, function, activation stage, and spatial distribution of the CAF subsets in GC is urgently needed. Methods: In this study, the characteristics of the CAF subsets and the dynamic communication among the tumor microenvironment (TME) components regulated by the CAF subsets were analyzed by performing single-cell RNA sequencing of eight pairs of GC and adjacent mucosal (AM) samples. The spatial distribution of the CAF subsets in different Lauren subtypes of GC, as well as the neighborhood relations between these CAF subsets and the protumor immune cell subsets were evaluated by performing multistaining registration. Results: Tumor epithelial cells exhibited significant intratumor and intertumor variabilities, while CAFs mainly exhibited intratumor variability. Moreover, we identified four CAF subsets with different properties in GC. These four CAF subsets shared similar properties with their resident fibroblast counterparts in the adjacent mucosa but also exhibited enhanced protumor activities. Additionally, two CAF subsets, inflammatory CAFs (iCAFs) and extracellular matrix CAFs (eCAFs), communicated with adjacent immune cell subsets in the GC TME. iCAFs interacted with T cells by secreting interleukin (IL)-6 and C-X-C motif chemokine ligand 12 (CXCL12), while eCAFs correlated with M2 macrophages via the expression of periostin (POSTN). eCAFs, which function as a pro-invasive CAF subset, decreased the overall survival time of patients with GC. Conclusions: iCAFs and eCAFs not only exhibited enhanced pro-invasive activities but also mobilized the surrounding immune cells to construct a tumor-favorable microenvironment. Therefore, inhibiting their activation restrains the GC 'seed' and simultaneously improves the 'GC' soil, suggesting that it represents a promising therapeutic strategy for the treatment of GC.

Discovering Immune-Mediated Mechanisms of Gastric Carcinogenesis Through Single-Cell RNA Sequencing

“…Among these infiltrated subsets, some T cells have been implicated in a tumor-promoting role and others in a tumorinhibiting role. CD4 + central memory precursor T cells (expressing CCR7, SELL, IL7R) were the most abundant subtype in tumor tissue, whereas the effector and effector memory T cells were abundant in the adjacent tissue (24). Similarly, a large number of Tregs showed infiltration into the tumor tissue compared to the adjacent tissue.…”

“…These observations suggest that the B cells may act in parallel to promote tumorigenesis, but their role might be dispensable (50,61). Once cancer is established in the tissue, the proportion of B cells decreases with disease progression (24). Additionally, the B cell phenotype changes from a proinflammatory state in the early stages of disease toward a proapoptotic state in advanced gastric cancer.…”

“…T cells are the most identified immune cells across all gastric cancer scRNAseq datasets using CD2 and CD3D. ScRNAseq analysis by Li et al (2022) reveals T cells as the most highly enriched immune cell population in the tumor microenvironment (TME), and their ratio increases as the disease advances (24). A greater diversity of unique T cell subsets and T cell receptor (TCR) repertoire were identified within tumor tissues when compared with that of patient-matched healthy tissue or peripheral blood mononuclear cells (PBMCs), suggesting that a variety of unique T cells infiltrate the TME (22).…”

“…utilized previously published M1/M2 signature datasets to conclude that after chemotherapy there is an increase in M1like TAMs and a decrease in M2-like TAMs, suggesting chemotherapy improves the anti-tumor TAM phenotype in patients who respond to treatment (33). Yet Li et al (2022) used the increased expression of CD163 to define one TAM cluster as M2s and found that the gene signature of these cells was associated with regulating immune infiltration into the TME (24). Chen et al (2019) created a novel in vitro p53 null murine gastric organoid model, containing epithelium with surrounding stroma, to study the gastric tissue microenvironment, in which M1-like macrophages, M2-like macrophages, and proliferating macrophages could all be identified by scRNAseq (52).…”

“…Among the published scRNAseq gastric cancer works, it is apparent that they have undertaken various approaches to their studies. Most groups obtained primary gastric cancer tissues from patients to generate scRNAseq data (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). Some utilized previously published primary tumor datasets for further analysis (36)(37)(38)(39)(40)(41)(42)(43).…”