Oncolytic Hairpin DNA Pair: Selective Cytotoxic Inducer through MicroRNA-Triggered DNA Self-Assembly.

Artificial nucleic acids have attracted much attention as potential cancer immunotherapeutic materials because they are recognized by a variety of extracellular and intracellular nucleic acid sensors and can stimulate innate immune responses. However, their low selectivity for cancer cells causes severe systemic immunotoxicity, making it difficult to use artificial nucleic acid molecules for immune cancer therapy. To address this challenge, we herein introduce a hairpin DNA assembly technology that enables cancer-selective immune activation to induce cytotoxicity. The designed artificial DNA hairpins assemble into long nicked double-stranded DNA triggered by intracellular microRNA-21 (miR-21), which is overexpressed in various types of cancer cells. We found that the products from the hairpin DNA assembly selectively kill miR-21-abundant cancer cells in vitro and in vivo based on innate immune activation. Our approach is the first to allow selective oncolysis derived from intracellular DNA self-assembly, providing a powerful therapeutic modality to treat cancer.

anti-syn Unnatural Base Pair Enables Alphabet-Expanded DNA Self-Assembly.

Self-assembly properties and diversity in higher-order structures of DNA enable programmable tools to be used to construct algorithms at the molecular level. However, the utility of DNA-based programmable tools is hampered by the low orthogonality to natural nucleic acids, especially in complex molecular systems. To address this challenge, we report here the orthogonal regulation of DNA self-assembly by using an unnatural base pair (UBP) formation. Our newly designed UBP AnN:SyN is formed in combination with anti and unusual syn glycosidic conformation with high thermal stability and selectivity. Furthermore, AnC worked as a pH-sensitive artificial nucleobase, which forms a strong base pair with cytosine under a weak acidic condition (pH 6.0). The orthogonal AnN:SyN base pair functioned as a trigger for hybridization chain reaction to provide long nicked double-stranded DNA (ca. 1000 base pairs). This work represents the first example of the orthogonal DNA self-assembly that is nonreactive to natural four-letter alphabets DNA trigger and expands the types of programmable tools that work in a complex environment.

Floxuridine Oligomers Activated under Hypoxic Environment.

Floxuridine oligomers are anticancer oligonucleotide drugs composed of a number of floxuridine residues. They show enhanced cytotoxicity per floxuridine monomer because the nuclease degradation of floxuridine oligomers directly releases highly active floxuridine monophosphate in cells. However, their clinical use is limited by the low selectivity against cancer cells. To address this limitation, we herein report floxuridine oligomer prodrugs that are active under hypoxia conditions, which is one of the distinguishing features of the microenvironment of all solid tumors. We designed and synthesized two types of floxuridine oligomer prodrugs that possess hypoxia-responsive moieties on nucleobases. The floxuridine oligomer prodrugs showed lower cytotoxicity under normoxia conditions (O2 = 20%), while the parent floxuridine oligomer showed similar anticancer effects under hypoxia conditions (O2 = 1%). The floxuridine oligomer prodrug enabled tumor growth suppression in live mice. This would be the first example demonstrating the conditional control of the medicinal efficacy of oligomerized nucleoside anticancer drugs.