PTK7 and neoplasm: Currently, a variety of aptamers targeting tumor cells have been screened by SELEX; for example, A10, anti-prostate-specific membrane antigen (PSMA) aptamer 72, AS1411, anti-nucleolin aptamer 73, 74, EpCAM, anti-epithelial cell adhesion molecule aptamer 75, 76, Sgc8, anti-protein tyrosine kinase 7 (PTK7) aptamer 77, 78, MUC1, anti-mucin1 aptamer 79, etc. Moreover, for these aptamers, a variety of drug delivery systems have been developed for targeted treatment of specific tumor cells.