PTK7 and cancer: Other cancer cell-specific aptamer targets exploited for AsiC experiments or in combination with other drugs include receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR; detected on glioma, lung, and breast cancer) [51,52], human epidermal growth factor receptor 2 (Erbb2 or HER2; particularly used for targeting breast cancer cells) [20], and tyrosine-protein kinase-like 7 (PTK7; overexpressed in many different cancers) [53].