Single-cell transcriptome analysis reveals evolutionarily conserved features during the transition from normal breast stromal cells to cancer-associated fibroblasts

Summary To comprehend cancer-associated fibroblasts (CAFs) origins, single-cell RNA sequencing was conducted on normal and cancerous breast tissue from mice and humans. We found three conserved CAF subtypes, which based on GOterm analysis we designated as matrix CAFs-, chemokine CAFs, and contractile CAFs. Matrix and chemokine CAFs originated from resident fibroblasts, while contractile CAFs originated from normal pericytes. Both human and mouse CAFs displayed upregulated genes involved in extracellular matrix organization, cellular respiration, and cell migration. Key transcription factors in both species included NFKB1, SP1, TP53, and TWIST2. Trajectory inference suggested that in some cases a transitory state characterized by JUN expression precedes the maturation of CAFs. Computational analysis revealed a common mechanism for CAF education involving the overexpression of TGF-β, PDGF, TNF, and NOTCH-family ligands in different tumor microenvironment cell types, along with reciprocal overexpression of receptors in CAFs. These findings bolster and broaden current understandings of CAF genesis.