Sequence-related off-target effect of Dz13 against human tumor cells and safety in adult and fetal mice following systemic administration.

The oligonucleotide Dz13, a DNA enzyme that cleaves c-Jun mRNA, is capable of inhibiting various model tumors in mice. However, to date, a thorough examination of its target specificity in tumor cells has not been performed. In addition, an evaluation of its safety in a mammalian whole organism system has not been carried out. Dz13 mutated oligonucleotides were designed and tested in a proliferation assay. Dz13 was also tested for its safety in vivo when administered intravenously in a bolus dose, or systemically in an in utero assay. While Dz13 down-regulated target gene (c-Jun) expression in human tumor cells, c-Jun siRNA failed to cause cell growth inhibition. Furthermore, alteration of contiguous G motifs in Dz13 flanking arms inhibits cell death activity, but removal of the same from the catalytic core can increase cell death activity. A 20mer (truncated) derivative Dz13 exhibited similar activity. Dz13 was not toxic to blood and solid tissues in adult or fetal mice, though slight hepatotoxicity was noted with histology. It was also void of adverse effects to the physiological processes of angiogenesis and apoptosis. Collectively, the data support the safety of Dz13 and its activity attributed to off-target effects.