Targeted immunotherapy of triple-negative breast cancer by aptamer-engineered NK cells.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer comprised of cells that lack expression of targetable biomarkers. Nucleic acid aptamers are a group of molecular ligands that can specifically bind to their targets with high affinity. The ssDNA aptamer PDGC21-T recognizes poorly differentiated cancer cells and tumor tissues through an unidentified cell surface target(s). Because TNBC tumor cells are poorly differentiated, the aptamer PDGC21-T is a promising therapeutic candidate to target TNBC tumor cells. In vitro study revealed that synthetic aptamer probes selectively targeted TNBC cell lines. To assess aptamer immunotherapeutic targeting capability, we generated aptamer-engineered NK cells (ApEn-NK) using aptamer probes as a targeting ligand and NK cells as a therapeutic agent. Cell clustering formation assays revealed that ApEn-NK bound both suspended and adherent TNBC cells with high affinity. In a functional study, ApEn-NK treatment triggered apoptosis and death of cultured TNBC cells. Finally, systemic administration of ApEn-NK in mice harboring TNBC xenografts resulted in significant inhibition of lung metastasis relative to parental NK cell treatments. Unlike chemotherapy, ApEn-NK treatment did not affect body weight in treated mice. We demonstrate a novel approach for targeted TNBC immunotherapy.