C5AR2 and breast cancer: To investigate whether the chemoresistance-inducing CD10+GPR77+ CAF subset was derived from normal breast tissues and activated or differentiated by the tumor microenvironment in situ, we isolated different cell types from normal breast tissues, including NBFs, pericytes, adipocytes, epithelial cells and endothelial cells, and mesenchymal stem cells (MSCs) from bone marrow, followed by treatment with the conditioned medium (CM) of fresh breast cancer tissues.