CXCL12 and breast neoplasm: CXCL12 expression is downregulated in primary breast carcinomas.23,24 Inactivation of the product of MAPK14 via PPM1D overexpression was also previously discovered in breast tumor cell lines.25 Supporting evidence for the role of NOTCH1 in breast cancer cells involves the fact that the rate of NOTCH1 expression in human breast cancer was found to be significantly higher than those of normal breast tissues at the margin of tumor sections.26 Zang et al27 showed that Notch signaling is overexpressed and highly activated in breast cancer.