CX3CL1 and breast cancer: Studies have found that CX3CR1-deficient mice exhibit a reduction in microglia numbers during postnatal development, suggesting CX3CL1-CX3CR1 signaling may serve as a chemoattractant to facilitate the microglia aggregation in the brain [41].In breast cancer research, scholars injected MDA-231 cells into the bloodstream of CX3CL1 knockout mice, resulting in a 70% reduction in bone metastatic foci compared to wild-type mice.