Scientists identify a delivery pathway for antisense therapies

Antisense oligonucleotides, or ASOs, are emerging as precision tools for suppressing disease-causing proteins, but their effectiveness depends on a difficult journey through the cell. A new study from researchers at the Cancer Research UK Scotland Institute and the University of Glasgow has identified a molecular route that helps an anticancer ASO reach its target inside pancreatic cancer cells. The findings, published in the Journal of Cell Biology, reveal how two cell-surface receptors guide the therapy into the cell, position it near the nucleus, and ultimately promote the release of the drug’s active molecules.

ASOs are short, chemically modified strands of DNA designed to recognize specific messenger RNA molecules. Messenger RNA carries genetic instructions from DNA to cellular protein-making machinery. When an ASO binds to its matching messenger RNA, the hybrid molecule can be recognized and destroyed by cellular enzymes, preventing production of the corresponding protein. This strategy has already shown promise in several inherited and neurodegenerative diseases, and researchers are investigating whether it can be used to silence mutant proteins that drive cancer growth.

The study focused on cET-ASO^KRas, an antisense drug developed by Ionis Pharmaceuticals to target messenger RNAs encoding mutant KRAS. KRAS proteins act as molecular switches that regulate cell growth and division. Mutations that lock KRAS in an active state can fuel uncontrolled proliferation and are common in pancreatic, colorectal, and lung cancers. In laboratory models, treatment with cET-ASO^KRas reduced mutant KRAS levels and inhibited the growth of pancreatic cancer cells and tumor-like spheroids.

Although ASOs are known to enter cells through endocytosis, the detailed trafficking process has remained poorly understood. During endocytosis, the cell surface folds inward and encloses external material in a membrane-bound compartment called an endosome. For an ASO to work, it must avoid being permanently trapped or degraded inside these compartments. It must instead reach the cell’s interior, escape from the endosome, and encounter its target messenger RNA in the cytoplasm or near the nucleus.

The researchers found that cET-ASO^KRas first binds to CD44, a receptor protein located on the surface of pancreatic cancer cells. CD44 is frequently abundant in aggressive tumors and has been associated with cancer stem-cell properties, nutrient uptake, invasion, and resistance to treatment. Binding to CD44 initiated a signaling cascade that activated a second receptor, EPHA2. This receptor then promoted the internalization of the ASO into endosomes and helped direct those endosomes toward the nucleus.

This positioning step proved critical. The nucleus is the compartment where most messenger RNA is produced and processed before being transported into the cytoplasm. By anchoring ASO-containing endosomes close to the nucleus, EPHA2 appears to place the therapeutic cargo near a major source of potential molecular targets. The study suggests that EPHA2 does more than participate in uptake: it acts as a trafficking organizer that determines where the ASO-containing compartments travel and how effectively the drug can reach the cell’s RNA.

Once near the nucleus, the endosomal membranes became damaged and leaky. This allowed cET-ASO^KRas to escape into the cytoplasm, where it could bind to mutant KRAS messenger RNA. The researchers demonstrated the importance of this pathway by removing CD44 or EPHA2 from pancreatic cancer cells. They also tested altered forms of EPHA2 that could no longer anchor endosomes near the nucleus. In each case, the ASO became less effective at lowering KRAS production and suppressing tumor growth.

The study also uncovered a cellular defense mechanism that limits antisense therapy. When endosomal membranes become leaky, the cell responds by forming stress granules, temporary assemblies of RNA and proteins that help protect and reorganize genetic messages during cellular stress. The researchers found that these structures can contribute to the repair or sealing of damaged endosomes, reducing the amount of ASO that escapes into the cytoplasm. In effect, the cell’s protective response can restrict the drug’s access to its target.

Blocking this response with ISRIB, a compound that inhibits stress-granule formation, enhanced the ability of cET-ASO^KRas to suppress KRAS production in laboratory experiments. The finding raises the possibility that drugs designed to improve endosomal escape could be combined with ASOs to increase their potency. However, because stress responses are also important for normal cell survival and tissue protection, such combinations would require careful testing to determine their safety and therapeutic window.

The researchers propose that the CD44–EPHA2 pathway could be exploited to improve the delivery of ASOs and other nucleic-acid medicines to aggressive tumors. Since both receptors are highly expressed in subsets of pancreatic cancer, they may provide a natural entry route that can be used to direct therapeutic molecules into particularly difficult-to-treat cells. The work does not yet establish an effective treatment for patients, but it identifies a series of molecular checkpoints that could guide the design of more efficient antisense therapies. By understanding how cancer cells import, transport, and restrict these drugs, scientists may be able to turn their own trafficking systems into a delivery advantage.

News Publication Date: 11 August 2026

Web References: Journal of Cell Biology: https://rupress.org/jcb ; DOI: https://doi.org/10.1083/jcb.202507217

References: Marco et al., 2026, Journal of Cell Biology, DOI: 10.1083/jcb.202507217