Aptamer-directed siRNA delivery systems for triple-negative breast cancer therapy

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the absence of estrogen, progesterone, and HER2 receptors, making it unresponsive to targeted hormonal and HER2-based therapies. Current treatment options, including chemotherapy and radiation, have limited efficacy and are associated with severe side effects, emphasizing the need for innovative therapeutic strategies. Aptamer-siRNA conjugates have emerged as a promising gene-silencing approach, leveraging the high specificity of nucleic acid aptamers to selectively deliver short interfering RNA (siRNA) to TNBC cells. Aptamers, single-stranded DNA or RNA molecules generated via SELEX, exhibit nanomolar-range binding affinities (Kd ∼0.5-2.5 nM) for TNBC biomarkers such as EGFR, EpCAM, nucleolin, and MUC1, enabling receptor-mediated internalization of siRNA. Preclinical studies have demonstrated that aptamer-siRNA conjugates enhance cellular uptake by 5-10-fold, improve gene silencing efficiency (80-95%), and extend siRNA stability in circulation (from <2 h to 6-9 h). In xenograft models, aptamer-siRNA therapies have shown tumor volume reductions of 60-85%, outperforming non-targeted siRNA and chemotherapy. However, challenges such as nuclease degradation, immune responses, endosomal escape, and large-scale production remain significant hurdles to clinical translation. Recent advances in chemical modifications, lipid-based carriers, and artificial intelligence-driven aptamer design are addressing these limitations, paving the way for personalized, precision RNAi-based therapeutics. This review explores the mechanisms, recent advancements, challenges, and future directions of aptamer-siRNA therapeutics, providing a comprehensive analysis of their potential to revolutionize TNBC treatment by offering targeted, effective, and less toxic gene-silencing approaches.