The initial in vitro evidence in this field has found that treatment of BM-MSCs with conditioned media of human breast cancer, pancreatic cancer, and glioma lead to the differentiation and expression of CAFs markers like α-SMA, fibroblast associated protein (FAP), fibroblast-specific protein 1 (FSP1) and vimentin (201). This evidence concerns the gene S100A4 and breast cancer.