CX3CL1 and nonpapillary renal cell carcinoma: The microarray data of patients with ccRCC from the GSE53757 (P <  0.001) and GSE40435 (P <  0.001) cohorts further validated the CX3CL1 expression difference between tumor and non-tumor tissue samples (Fig. 2C–D); the expression of CX3CL1 was significantly higher in tumor tissues than in normal tissues.