CXCL12 and cancer: Moreover, αSMA+ fibroblasts produce high amounts of CXCL12/SDF1 and IGF1, which select cancer cells with high Src activity prone to colonize CXCL12/SDF1-rich bone marrow microenvironment, further suggesting a potential role of primary tumor CAFs in educating BrCa cells to metastasize to the bone microenvironment [121].