Single-cell transcriptome sequencing reveals spatial distribution of IL34+ cancer-associated fibroblasts in hepatocellular carcinoma tumor microenvironment.

ABSTRACT

We utilized scRNA-seq, a well-established technology, to uncover the gene expression characteristics of IL34+ CAFs within HCC. We analyzed the related mechanisms through in vitro and in vivo assays. To begin, we acquired scRNA-seq datasets about HCC, which enabled us to identify distinct cell subpopulations within HCC tissues. We conducted a differential analysis to pinpoint DEGs associated with normal fibroblasts (NFs) and CAFs. Subsequently, we isolated NFs and CAFs, followed by the sorting of IL34+ CAFs. These IL34+ CAFs were then co-cultured with T cells and HCC cells to investigate their potential role in Tregs infiltration, CD8+ T cell toxicity, and the biological processes of HCC cells. We validated our findings in vivo using a well-established mouse model. Our analysis of HCC tissues revealed the presence of seven primary cell subpopulations, with the most significant disparities observed within fibroblast subpopulations. Notably, high IL34 expression was linked to increased expression of receptor proteins and enhanced proliferative activity within CAFs, with specific expression in CAFs. Furthermore, we identified a substantial positive correlation between IL34 expression and the abundance of Tregs. Both in vitro and in vivo experiments demonstrated that IL34+ CAFs promoted Tregs infiltration while suppressing CD8+ T cell toxicity. Consequently, this promoted the growth and metastasis of HCC. In summary, our study affirms that IL34+ CAFs play a pivotal role in augmenting the proliferative activity of CAFs, facilitating Tregs infiltration, and inhibiting CD8+ T cell toxicity, ultimately fostering the growth and metastasis of HCC.