CX3CL1 and breast cancer: The level of CX3CL1 in the serum samples from the metastatic spinal tumors was 0.63 ± 0.05 ng/ml in lung cancer, 0.61 ± 0.08 ng/ml in liver cancer, 0.58 ± 0.06 ng/ml in breast cancer, 0.69 ± 0.13 ng/ml in kidney cancer, and 0.71 ± 0.12 ng/ml in prostate cancer.