CCN1 and breast cancer: To test whether CYR61 might also promote metastasis of breast cancer growing in a pre-irradiated bed mimicking the breast cancer tumor microenvironment, we orthotopically injected NS and CYR61 KD MDA-MB-231 cells into 20 Gy pre-irradiated mammary fat pads (MFPs) of NSG mice (Figure 1A).