Single Shot vs. Cocktail: A Comparison of Mono- and Combinative Application of miRNA-Targeted Mesyl Oligonucleotides for Efficient Antitumor Therapy

SIMPLE SUMMARY: Current approaches to the treatment of oncological diseases are still suffering from a lack of efficiency and selectivity and are accompanied by pronounced non-specific toxic effects. This study evaluated the antitumor potential of highly selective multitarget antisense downregulation of small non-coding RNA molecules—microRNAs—where dysregulation in cells frequently triggers oncotransformation and tumor development. We report herein that combinations of recently developed mesyl phosphoramidate oligonucleotides, targeted to multifunctional miRNA regulators miR-17, miR-21 and miR-155, exhibited potent synergistic antiproliferative and antimigrative effects on highly aggressive tumor cells. Furthermore, the significant antitumor activity of a cocktail of three antisense oligonucleotides targeted to miR-21, miR-17, and miR-155 almost completely suppressed lymphosarcoma RLS(40) tumor growth and exerted prominent antimetastatic effects in a melanoma B16 model. Such treatment elicited no sign of in vivo toxicity and even exhibited remedial effects on the liver of tumor-bearing mice. ABSTRACT: Rational combinations of sequence-specific inhibitors of pro-oncogenic miRNAs can efficiently interfere with specific tumor survival pathways, offering great promise for targeted therapy of oncological diseases. Herein, we uncovered the potential of multicomponent therapy by double or triple combinations of highly potent mesyl phosphoramidate (µ) antisense oligodeoxynucleotides targeted to three proven pro-oncogenic microRNAs—miR-17, miR-21, and miR-155. A strong synergism in the inhibition of proliferation and migration of B16 melanoma cells was demonstrated in vitro for pairs of µ-oligonucleotides, which resulted in vivo in profound inhibition (up to 85%) of lung metastases development after intravenous injection of µ-oligonucleotide-transfected B16 cells in mice. A clear benefit of µ-21-ON/µ-17-ON and µ-17-ON/µ-155-ON/µ-21-ON combination antitumor therapy was shown for the lymphosarcoma RLS(40) solid tumor model. In vivo administration of the µ-17-ON/µ-155-ON/µ-21-ON cocktail into RLS(40)-bearing mice elicited fourfold delay of tumor growth as a result of strong inhibition of tumor mitotic activity. It was discovered that the cocktail of µ-21-ON/µ-17-ON/µ-155-ON led to a twofold decrease in total destructive changes in murine liver, which indicates both the reduction in toxic tumor burden and the absence of specific toxicity of the proposed therapy.