PTPN22 and neoplasm: In addition to LyP-1, the RGD peptide, a tripeptide consisting of L-arginine, glycine and L-aspartic acid, is a cell adhesion sequence that mimics cell adhesion proteins and can bind to integrin receptors on angiogenic endothelial cells and tumor cells, such as malignant glioblastoma cells, bladder cancer cells and αVβ3 integrin receptor-overexpressing breast cancer cells [65].