MAPK1 and breast cancer: With p-CREB as a target, CHIP assay showed a physical interaction between p-CREB and the CXCR4 promoter when 5637 cells were stimulated with MSP, which activated RON and upstream ERK/RSK2/CREB (Figure 5C), providing direct evidence that RON act as a key regulator in promoting CXCR4 expression in BC cells.