HAO2 and nonpapillary renal cell carcinoma: Hydroxyacid oxidase 2 (HAO2) encodes peroxisomal proteins with 2-hydroxy acid oxidase activity, which participated in the production of reactive oxygen species and cellular breakdown22; HAO2 has already been shown downregulated in hepatocellular carcinoma (HCC) tissues and ccRCC, overexpression of which restrained HCC and RCC cells proliferation by eliminating lipid droplet accumulation23,24.