PTK7 and leukemia: Tenascin-C is widely used in tumor diagnosis and therapy.45 Using cell-SELEX selection, protein tyrosine kinase 7 (PTK7), a transmembrane receptor protein tyrosine kinase-like molecule, was identified in a T-cell acute lymphoblastic leukemia (T-ALL) cell line (CCRF-CEM).46 Specifically, aptamer sgc8c binds to PTK7 on the leukemia cell surface.