Numerous types of oligonucleotide modifications have been developed since automated synthesis of DNA/RNA became a common instrument in the creation of synthetic oligonucleotides. Despite the growing number of types of oligonucleotide modifications under development, only a few of them and, moreover, their combinations have been studied widely enough in terms of their influence on the properties of corresponding NA constructions. In the present study, a number of oligonucleotides with combinations of 3′-end lipophilic (a single cholesteryl or a pair of dodecyl residues) and phosphate backbone modifications were synthesized. The influence of the combination of used lipophilic groups with phosphate modifications of various natures and different positions on the efficiency of cell penetration was evaluated. The obtained results indicate that even a couple of phosphate modifications are able to affect a set of oligonucleotide properties in a complex manner and can remarkably change cellular uptake. These data clearly show that the strategy of using different patterns of modification combinations has great potential for the rational design of oligonucleotide structures with desired predefined properties.

Lipophilic oligonucleotide conjugates represent a powerful tool for nucleic acid cellular delivery, and many methods for their synthesis have been developed over the past few decades. In the present study, a number of chemical approaches for the synthesis of different fork- and comb-like dodecyl-containing oligonucleotide structures were performed, including use of non-nucleotide units and different types of phosphate modifications such as alkyl phosphoramidate, phosphoryl guanidine, and triazinyl phosphoramidate. The influence of the number of introduced lipophilic residues, their mutual arrangement, and the type of formed modification backbone on cell penetration was evaluated. The results obtained indicate great potential in the developed chemical approaches, not only for the synthesis of complex oligonucleotide structures but also for the fine-tuning of their properties.

Background and Objectives: Aggressive cancer development is characterized by rapid tumor growth and progressive immune dysfunction. Tumor-derived microRNAs (miRNAs) emerge as master regulators of both malignant transformation and immune evasion, making them promising therapeutic targets. Using the highly aggressive CT-26 peritoneal adenomatosis model, this study explored the potential of selective miRNA inhibition to simultaneously suppress tumor growth and overcome immunosuppression. Methods and Results: Our results revealed that inhibition of miR-155, miR-21, and miR-17 by methylsulfonyl phosphoramidate (mesyl) oligonucleotides exhibited markedly different therapeutic profiles. miR-155 inhibition demonstrated minimal efficacy. miR-21 suppression provided early tumor regression and prevented cancer-associated thymic atrophy, translating into extended survival. miR-17 inhibition displayed delayed but superior tumor growth inhibition, significantly reducing pathologically elevated polymorphonuclear myeloid-derived suppressor cell (MDSC) populations, and nearly doubled animal lifespan. Combination therapy targeting all three miRNAs integrated these complementary mechanisms, maintaining consistent anti-tumor efficacy across early and late stages while providing thymic protection and MDSC reduction. Importantly, therapeutic responses in vivo substantially exceeded predictions based on in vitro tumor cell proliferation and motility measurements, revealing critical contributions of systemic immunomodulation. Conclusions: These findings demonstrate that miRNA inhibition reshapes tumor–immune interactions, positioning anti-miRNA therapeutics as immunomodulatory agents for effective colorectal cancer treatment.

Numerous types of oligonucleotide modifications have been developed since automated synthesis of DNA/RNA became a common instrument in the creation of synthetic oligonucleotides. Despite the growing number of types of oligonucleotide modifications under development, only a few of them, and moreover, their combinations have been studied wide enough in terms of their in-fluence on the properties of corresponding NA constructions. In the present study, a number of oligonucleotides with combinations of 3′ end lipophilic (single cholesteryl or pair of dodecyl residues) and phosphate backbone modifications were synthesized. The influence of the combi-nation of used lipophilic groups with phosphate modifications of various nature and different position on the efficiency of cell penetration was evaluated. Obtained results indicate that even a couple of phosphate modifications are able to affect a set of oligonucleotide properties in a complex manner and can remarkably change cellular uptake. These data clearly show that the strategy of using different patterns of modification combinations has great potential for the ra-tional design of oligonucleotide structures with desired predefined properties.