DNA nanostructure-based drug delivery system (DDS) has become an advanced therapeutic strategy for cancer because of its unsurpassed editability, intrinsic biodegradability, and tunable multifunctionality. An intelligent DNA nanosystem integrating targeting, immunostimulation, and chemotherapy was constructed based on unmethylated cytosine-phosphate-guanine oligonucleotides (CpG ODNs) DNA nanohydrogels (CpG-MUC1-hydrogel). By facile one-step self-assembly, the cross-shaped DNAs (C-DNAs) assembled from pH-responsive I-motif sequences and targeted MUC1 aptamer-immunoadjuvant CpG-fused sequences (CpG-MUC1) were integrated into DNA nanohydrogels with controllable size by the hybridization of DNA linkers. Subsequently, DOX was successively intercalated into the base pairs of CpG-MUC1-hydrogel, resulting in CpG-MUC1-hydrogel/Dox that would disassemble and release DOX and CpGs at acidic conditions. After MUC1-mediated internalization, CpG-MUC1-hydrogel/Dox dissociated in the endo/lysosomes and induced favorable apoptosis of tumor cells. Afterward, liberated CpGs triggered vast cytokine secretion from immune cells which elicited potent immune response against malignancy. Notably, CpG-MUC1-hydrogel induced an apoptosis effect on MCF-7 cells via significantly increasing the Bax/Bcl2 ratios and a higher level of tumor necrosis factor (TNF-α) on RAW264.7 cells than naked CpGs. Our results demonstrated that self-assembled CpG-MUC1-hydrogel represented an attractive DDS for precise delivery, potent immunostimulating activity, and considerable combination efficiency with few adverse effects, which is expected to make breakthroughs in clinical translation.
Keywords: antitumor mechanisms; co-delivery systems; combination therapy; immunostimulation; multifunctional DNA nanohydrogels.