TGFB1 and nonpapillary renal cell carcinoma: Figure 4 also illustrates the potential role of TGF-β in inducing the epithelial-to-mesenchymal transition [64,65], P-glycoprotein [66], nuclear factor-erythroid factor 2-related factor 2, macrophage [46], glycogen synthase kinase [67], and mitochondrial lipid metabolizing enzymes that regulate the stable accumulation of lipid droplets, which is a unique histological feature associated with ccRCC [2,3].