Derepression of co-silenced tumor suppressor genes by nanoparticle-loaded circular ssDNA reduces tumor malignancy.

The co-silencing of multiple tumor suppressor genes can lead to escalated malignancy in cancer cells. Given the limited efficacy of anticancer therapies targeting single tumor suppressor genes, we developed small circular single-stranded DNA (CSSD) that can up-regulate the expression of co-silenced tumor suppressor genes by sequestering microRNAs (miRNAs) that negatively regulate these genes. We found that cancer patients with low tumor expression of the tumor suppressor genes KLF17, CDH1, and LASS2 had shortened survival times. The up-regulation of these genes upon transfection of artificial CSSD-9 inhibited tumor proliferation and metastasis and promoted apoptosis in vitro as well as in ex vivo and patient-derived xenograft models. In addition, CSSD is more stable and effective than current miRNA inhibitors, and transfecting CSSDs via nanoparticles substantially improved delivery efficiency. The use of a single CSSD can promote the inhibition of multiple tumor suppressor genes. This study provides evidence for the possibility of using CSSDs as therapeutic miRNA inhibitors to target the co-silencing of multiple tumor suppressor genes.