Selection and validation of a cell-internalizing DNA aptamer targeting esophageal squamous cell carcinoma.

Esophageal squamous cell carcinoma (ESCC) is the main histological subtype of esophageal cancer and one of the major causes of cancer-related death worldwide. Currently, an effective targeted therapy for ESCC is still lacking. Aptamers have been widely used as an effective tool to identify cell surface targets because of their high affinity and specificity. Accordingly, screening internalized aptamers targeting ESCC can promote the development of targeted drug delivery for this disease. Taking KYSE450 cells as the targets, we used the cell-based Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) protocol combined with a cell internalization strategy to screen aptamers. After 17 rounds of positive and negative strict screening, we confirmed that the best candidate aptamer was Ap1 and obtained its derived aptamer Ap1-1 through sequence optimization. In vitro experiments showed that Ap1-1 could bind many ESCC cell lines, and its dissociation constant was as low as 22.54 nmol/L, showing excellent cell-internalization ability. In an ESCC xenograft tumor model, Ap1-1 showed significant tumor targeting, and its accumulation in tumor tissue was significantly higher than that in the liver, kidney, and other organs 24 h after administration, indicating that it may have a long half-life in vivo and favorable pharmacokinetic characteristics. Based on the excellent tumor-targeting and internalization properties of aptamer Ap1-1, it is expected to be developed as a new molecular tool for targeted therapy and provide a new strategy for precise ESCC treatment.