Affibody molecules have been isolated and shown to be able to target tumors having expression of CAIX33, 54 and PDGFR.55, 56, 57 As expression levels of VEGFR2 are low, and available only in a small cell population within the tumor, efforts have been directed towards enhancing the affinity of the VEGFR2-specific Affibody molecule. This evidence concerns the gene PDGFRB and neoplasm.