Several aptamers targeting human epidermal growth factor receptor 2 (HER2) have been developed but most of them were used to deliver anticancer therapeutics such as cytotoxic agents, therapeutic RNAs, and nanoparticles into cancer cells instead of inhibiting HER2 function directly and so will not be discussed here; readers can refer to the relevant sections and to Table 2. This evidence concerns the gene ERBB2 and cancer.