Antisense oligonucleotides (ASOs) have been proposed as a therapeutic approach to shut down the production of faulty proteins in a wide variety of diseases, including cancer. In a study to be published August 11 in the Journal of Cell Biology (JCB), researchers at the Cancer Research UK Scotland Institute and the University of Glasgow identify a pathway by which ASOs enter cells and reach their targets, suggesting new ways to enhance the effectiveness of antisense therapy.

ASOs are short strands of DNA designed to bind to specific protein-encoding messenger RNAs (mRNAs) inside cells. The resulting DNA–mRNA complexes can then be degraded by a cellular enzyme, preventing the mRNA from being used to generate a disease-causing protein. This could potentially halt the production of toxic proteins that underlie certain neurodegenerative disorders or switch off the expression of mutant proteins driving proliferation of cancer cells.

ASOs are taken up into cells via a process known as endocytosis. But exactly how this happens, and how the ASOs subsequently find their target mRNA, is unclear.

Despite the importance of endocytic trafficking for ASO efficacy, the mechanisms governing their uptake and intracellular routing remain poorly understood."

Jim C. Norman, Professor, Cancer Research UK Scotland Institute and University of Glasgow

Norman and colleagues, led by postdoctoral researcher Sergi Marco and conducted in collaboration with Ionis Pharmaceuticals, studied an ASO called cET-ASOKRasKRas

The researchers found that cET-ASOKRasKRasKRas

Norman and colleagues found that interfering with this pathway by deleting CD44 or EPHA2 from pancreatic cancer cells, or expressing mutants of EPHA2 that cannot anchor ASO-containing endosomes to the nucleus, prevented cET-ASOKRas

However, the researchers discovered that cells also have their own way of limiting the pathway and reducing the effectiveness of ASOs. When endosomes near the nucleus become leaky, cells initiate the formation of structures called stress granules that plug and repair the endosome membrane. Norman and colleagues found that blocking stress granule formation with a drug called ISRIB enhanced the ability of cET-ASOKras

Notably, CD44 and EPHA2 are both highly expressed in aggressive pancreatic cancers. CD44, in particular, is thought to promote tumor growth by promoting nutrient uptake and maintaining therapy-resistant cancer stem cells. "We propose that this receptor, which has been selected by pancreatic tumors for its ability to support tumor stemness and growth, could be exploited as a gatekeeper to an endocytic pathway capable of delivering therapeutic molecules like cET-ASOKras

"Our finding that chemical inhibition of the pathway that repairs endosomal membranes increases cET-ASOKRas

Source:

Journal reference:

Sergi, M., et al. (2026). EPHA2/CD44-directed trafficking enhances endosomal leakiness and antisense therapy delivery. Journal of Cell Biology. DOI: 10.1083/jcb.202507217. https://rupress.org/jcb/article/225/9/e202507217/282905/EPHA2-CD44-directed-trafficking-enhances-endosomal