ACTA1 and triple-negative breast carcinoma: Subclass CAF-S1 positive for FAP and α-SMA and subclass CAF-S4 FAP negative and α-SMA positive were detected enriched in TME triple-negative breast cancer, and of these two subpopulations, CAF-S1 stands out for having an immunosuppressive role by mainly recruiting regulatory T cells through the secretion of C-X-C motif chemokine ligand 12 (CXCL12) (93).