The mechanisms governing the stable regulation of SDF-1 in breast cancer-associated myofibroblasts have not been established; however, it is speculated that destruction of tumor cells by chemotherapeutic agents may release tumor-associated antigens, triggering an immune response that regulates SDF-1, which is particularly strong in patients whose immune systems are sensitive to certain tumor antigens before the onset of chemotherapy. The gene discussed is CXCL12; the disease is neoplasm.