MiR-21 is upregulated in RCC, targeting PTEN and PDCD4, and miR-106a is downregulated, targeting PAK5 in the RAS/MAPK signaling pathway; the serum levels of both are higher in patients with RCC compared to those of the controls, and levels decreased after RCC resection [55,56]. Here, PDCD4 is linked to renal cell carcinoma.