RRAS2 and autosomal dominant polycystic kidney disease: Of note, some of the genes with the greatest fold change in expression were rras2, tgfα, ntrk3a, tcirg1b, and vegefα. Of these genes, serum VEGFα serves as a biomarker for ADPKD progression (Reed et al., 2011; Leierer et al., 2021); Tgfα is upregulated in the cystic epithelia of PKD patients and transgenic overexpression of Tgfα promotes renal cyst formation (Gattone et al., 1996; Lee et al., 1998).