PLK4 and nonpapillary renal cell carcinoma: The predicted methylation sites of PLK4 showed three sites with high methylation levels in ccRCC include cg22112850, cg06015521, and cg26882168, of which the highest methylation level was found at cg22112850 (Figure 4(e)), indicating that the methylation level of PLK4 at this CpG site is mostly correlated with the prognosis of ccRCC (Table 1).