TGF-β1 induces autophagy and mediates the effect on macrophages differentiation in primary liver cancer.

BACKGROUNDTumor-associated macrophages (TAMs) are closely associated with tumor development and patient outcomes due to their plasticity and polarization capacity. Several distinct TAMs have been proposed, but a complete understanding of heterogeneity and differentiation spectrum of macrophage in human primary liver cancer remains elusive.

METHODSDeep single-cell RNA sequencing (scRNA-seq) data from 19 primary liver cancer patients were used to profile the transcriptomes of TAMs in liver cancer. Ingenuity pathway analysis (IPA) and in vitro experiments were used to explore possible mechanisms responsible for related signaling pathways altered at the transcriptional level. Finally, we analyzed the relationship between the abundance of the TAMs and the survival outcomes of the 428 patients in the Cancer Genome Atlas (TCGA).

RESULTSTranscriptional profiles allowed us to identify four distinct TAMs cell subsets based on molecular and functional properties and to reconstruct their developmental trajectory. Specifically, TAM_c4 was preferentially enriched and potentially expanded in the advanced-stage patients or those receiving immune checkpoint blockade therapy (ICT). Gene pathway analysis revealed aberrant TGFB1 activation in TAM_c4, which was experimentally confirmed to drive TAM phenotypic transitions via autophagy signaling. High abundance of TAM_c4 is found to be related to a short survival time and low abundance of CD8+ T cells in primary liver cancers.

CONCLUSIONSThis integrated transcriptome compendium and experimental validation offer both mechanistic insights and a resource for understanding TAM heterogeneity in primary liver cancers.