KDR and colorectal cancer: Given the observed overexpression of PDGF receptors and VEGF receptors in human colon cancer tumors, we assessed the protein expression of PDGFRα, PDGFRβ, VEGFR1, and VEGFR2 in established human colorectal cancer cell lines ranging from more differentiated and less metastatic HT29 and Caco-2 cells to the poorly differentiated SW480 cells.