siRNA conjugated to nuclear export signal peptides suppressed the BCR/ABL leukemia gene by up to 96% in human CML cells, dramatically outperforming unconjugated siRNA at the same doses.
96% Gene SilencingsiRNA linked to an HIV-1 REV nuclear export signal peptide suppressed the BCR/ABL leukemia gene to just 4% expression at 200 nM, vs. 36% with unmodified siRNA
What the researchers found
Two siRNA-NES peptide conjugates were synthesized: one linked to a TFIIIA-derived NES peptide and another to an HIV-1 REV-derived NES peptide. The HIV-1 REV conjugate suppressed BCR/ABL expression to 4.0% (96% silencing) at 200 nM and 6.3% at 50 nM. The TFIIIA conjugate suppressed to 8.3% at 200 nM and 11.6% at 50 nM. By comparison, native siRNA only suppressed to 36.3% at 200 nM and 30.2% at 50 nM. Complexing the conjugates with amphiphilic peptideβ7 enabled non-toxic cellular uptake with excellent silencing efficiency.
Why it matters
Gene silencing with siRNA has enormous therapeutic potential but is limited by poor cellular uptake and intracellular trafficking. By conjugating siRNA to NES peptides, the researchers achieved near-complete gene silencing at standard doses — and the peptide-based delivery system avoids the toxicity associated with lipid-based transfection agents. This could advance gene therapy for CML and other cancers driven by known gene fusions.
How the study worked
Researchers synthesized siRNA-NES peptide conjugates using solid-phase fragment coupling, linking NES peptides (from TFIIIA and HIV-1 REV) to the 5' end of sense strands. They tested gene silencing efficiency in human CML cell line K562 at multiple concentrations. Cellular uptake was achieved using complexation with an amphiphilic carrier peptide (peptideβ7), and cytotoxicity was assessed.
What this study cannot tell us
This is an in vitro study using a single cell line (K562), and results need validation in animal models and other CML cell lines. The study did not assess off-target gene silencing effects. In vivo pharmacokinetics, biodistribution, and immune responses to the peptide-siRNA conjugates are unknown. The amphiphilic peptide delivery system needs further optimization for in vivo use.
How to read the evidence
This is an in vitro proof-of-concept study in a single cell line. While the gene silencing results are striking, the approach has not been tested in animal models or clinical settings.
When this study was published
Published in 2017, this study demonstrated early proof of concept for NES peptide-siRNA conjugates. The peptide-oligonucleotide conjugate field has continued to advance since publication.
The bigger picture
Peptide-nucleic acid conjugates represent a growing class of therapeutics that combines the targeting precision of peptides with the gene-modulating power of oligonucleotides. This study's success in dramatically improving siRNA potency through simple peptide conjugation validates the approach and could be applied to other gene targets beyond BCR/ABL — potentially advancing personalized gene therapy for various cancers.
Questions still open
- Can these peptide-siRNA conjugates achieve similar gene silencing levels in vivo in animal models of CML?
- Would this approach work for other oncogenic fusion genes beyond BCR/ABL?
- How does the peptideβ7 delivery system compare to newer peptide and nanoparticle delivery methods?
Common questions
How do peptides improve gene silencing?
Could this approach treat leukemia?
Read the original research
Silencing of BCR/ABL Chimeric Gene in Human Chronic Myelogenous Leukemia Cell Line K562 by siRNA-Nuclear Export Signal Peptide Conjugates.
Nucleic acid therapeutics, 27(3), 168-175
Citation
Shinkai, Yasuhiro; Kashihara, Shinichi; Minematsu, Go; Fujii, Hirofumi; Naemura, Madoka; Kotake, Yojiro; Morita, Yasutaka; Ohnuki, Koichiro; Fokina, Alesya A; Stetsenko, Dmitry A; Filichev, Vyacheslav V; Fujii, Masayuki. (2017). Silencing of BCR/ABL Chimeric Gene in Human Chronic Myelogenous Leukemia Cell Line K562 by siRNA-Nuclear Export Signal Peptide Conjugates.. Nucleic acid therapeutics, 27(3), 168-175. https://doi.org/10.1089/nat.2016.0647