Targeting Cancer Gene Dependencies with Anthrax-Mediated Delivery of Peptide Nucleic Acids

• Published in: ACS chemical biology Vol. 15; no. 6; pp. 1358 - 1369
• Main Authors: Lu, Zeyu, Paolella, Brenton R, Truex, Nicholas L, Loftis, Alexander R, Liao, Xiaoli, Rabideau, Amy E, Brown, Meredith S, Busanovich, John, Beroukhim, Rameen, Pentelute, Bradley L
• Format: Journal Article
• Language: English
• Published: United States 19-06-2020
• Subjects: Antigens, Bacterial - chemistry; Bacterial Toxins - chemistry; Cell Line, Tumor; Cell Survival - drug effects; Drug Carriers - chemistry; Drug Delivery Systems; Genetic Therapy; Humans; Neoplasms - genetics; Neoplasms - therapy; Oligonucleotides, Antisense - administration & dosage; Oligonucleotides, Antisense - pharmacology; Peptide Nucleic Acids - administration & dosage; Peptide Nucleic Acids - pharmacology; Phosphoproteins - genetics; RNA Splicing Factors - genetics
• ISSN: 1554-8929; 1554-8937
• DOI: 10.1021/acschembio.9b01027

Antisense oligonucleotide therapies are important cancer treatments, which can suppress genes in cancer cells that are critical for cell survival.
has recently emerged as a promising gene target that encodes a key splicing factor in the SF3B protein complex. Over 10% of cancers have lost one or more copies of the
gene, rendering these cancers vulnerable after further suppression.
is just one example of a CYCLOPS (Copy-number alterations Yielding Cancer Liabilities Owing to Partial losS) gene, but over 120 additional candidate CYCLOPS genes are known. Antisense oligonucleotide therapies for cancer offer the promise of effective suppression for CYCLOPS genes, but developing these treatments is difficult due to their limited permeability into cells and poor cytosolic stability. Here, we develop an effective approach to suppress CYCLOPS genes by delivering antisense peptide nucleic acids (PNAs) into the cytosol of cancer cells. We achieve efficient cytosolic PNA delivery with the two main nontoxic components of the anthrax toxin: protective antigen (PA) and the 263-residue
-terminal domain of lethal factor (LF
). Sortase-mediated ligation readily enables the conjugation of PNAs to the C terminus of the LF
protein. LF
and PA work together in concert to translocate PNAs into the cytosol of mammalian cells. Antisense
PNAs delivered with the LF
/PA system suppress the
gene and decrease cell viability, particularly of cancer cells with partial copy-number loss of
. Moreover, antisense
PNAs delivered with a HER2-binding PA variant selectively target cancer cells that overexpress the HER2 cell receptor, demonstrating receptor-specific targeting of cancer cells. Taken together, our efforts illustrate how PA-mediated delivery of PNAs provides an effective and general approach for delivering antisense PNA therapeutics and for targeting gene dependencies in cancer.