AOX1 and nonpapillary renal cell carcinoma: Similarly, we observed significantly higher methylation levels in four CpG sites (cg26961824, cg01217071, cg27547291, and cg22953017) of the AOX1 gene in ccRCC with lower AOX1 expression levels compared with ccRCC with higher AOX1 expression levels, and the methylation level shows a moderate negative correlation with the AOX1 gene expression.