Targeting Oncogenic KRAS Using Peptide Nucleic Acid Oligomers Attached to Cell-Penetrating Peptides

Approximately 30% of tumors contain an activating mutation in the oncogene KRAS, leading to increased cell proliferation that often promotes non-small cell lung cancers, colorectal adenocarcinomas, pancreatic ductal adenocarcinomas (PDAC), and other cancers. Among the most common point mutations in KRAS is G12D, an example of an oncogenic sequence present in tumor cells but not normal cells. We developed peptide nucleic acid (PNA) oligomers that selectively bind KRAS G12D sequences and fused them with novel cell-penetrating peptide flanking regions (CPP-PNA-G12D) then evaluated them. Electrophoretic mobility shift assays demonstrated in vitro binding to and selectivity for KRAS G12D over wild-type KRAS and KRAS G12C. Cells and nuclei were able to uptake CPP-PNA-G12D at high efficiency as shown by fluorescent microscopy and flow cytometry. Cell viability assays showed a striking dose-response effect in on-target cells expressing KRAS G12D, while relatively sparing off-target cells expressing KRAS G12C. CPP-PNA-G12D constructs were effective against a panel of PDAC cell lines and in female Balb/c mice bearing patient-derived xenografts. These results show promise for an enhanced PNA-delivery peptide conjugate strategy as a potential therapeutic strategy to selectively target KRAS mutant cancer cells, with the potential to expand this technology to additional cancer-derived mutant oncogenes.