Researchers Uncover CD44–EPHA2 Endosomal Pathway That Could Unlock Antisense Therapy for Cancer
核心洞察
A study in the Journal of Cell Biology identifies a previously unknown trafficking pathway by which antisense oligonucleotides (ASOs) enter pancreatic cancer (搜索) cells and reach their RNA targets.
Researchers found that a KRAS (搜索)-targeting ASO binds the cell-surface receptor CD44, activating EPHA2 (搜索) to anchor ASO-containing endosomes near the nucleus, where lipid peroxidation allows escape into the cytoplasm.
Deleting CD44 or EPHA2 (搜索), or blocking stress granule formation with the drug ISRIB, modulated the ASO's ability to suppress mutant KRAS (搜索) and inhibit tumor growth.
Antisense oligonucleotides (ASOs) can selectively switch off disease-causing genes, yet their success in oncology has been limited by a fundamental challenge: scientists have not fully understood how these short strands of DNA enter cells, escape intracellular compartments, and reach their RNA targets. A new study published in the Journal of Cell Biology identifies a previously unknown trafficking pathway that could help overcome this barrier.
Researchers from the Cancer Research UK Scotland Institute (搜索), the University of Glasgow, and collaborators at Ionis Pharmaceuticals (搜索) found that a KRAS (搜索)-targeting ASO follows a specific route into pancreatic cancer (搜索) cells that is essential for silencing the cancer-driving gene. The study, led by postdoctoral researcher Sergi Marco and conducted in collaboration with Ionis Pharmaceuticals, was carried out under Jim C. Norman, Professor at the Cancer Research UK Scotland Institute and University of Glasgow.
A Pathway from Cell Surface to Nucleus
Although ASOs have transformed treatment for several rare genetic diseases, progress in cancer has been slower because most molecules become trapped inside membrane-bound endosomes after entering tumor cells. Only a small fraction escapes into the cytoplasm or nucleus, where ASOs bind messenger RNA (mRNA) and trigger its degradation. Improving intracellular delivery is widely considered one of the biggest challenges in advancing ASO therapies for cancer.
Using a constrained ethyl ASO targeting mutant KRAS (搜索)—called cET-ASOKRas (搜索) and developed by Ionis—the team discovered that productive uptake begins when the ASO binds directly to the cell-surface receptor CD44. This interaction activates signaling that phosphorylates a second receptor, EPHA2 (搜索), which then directs ASO-containing endosomes to accumulate near the nucleus. Once positioned near the nucleus, the endosomal membranes undergo lipid peroxidation, making them leaky and allowing the ASOs to escape into the cell, where they can bind their target mRNA and suppress KRAS expression.
Functional Validation of the Pathway
Norman and colleagues found that interfering with this pathway by deleting CD44 or EPHA2 (搜索) from pancreatic cancer (搜索) cells, or expressing mutants of EPHA2 that cannot anchor ASO-containing endosomes to the nucleus, prevented cET-ASOKRas (搜索) from reducing KRAS (搜索) levels and inhibiting tumor growth. Treating pancreatic cancer cells with cET-ASOKRas reduces mutant KRAS levels and inhibits tumor growth in the lab.
A Cellular Brake on ASO Efficacy
The researchers also discovered that cells 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 (搜索) to suppress KRAS (搜索) production.
Clinical Implications for Aggressive Tumors
Notably, CD44 and EPHA2 (搜索) 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 (搜索) to aggressive tumors," said Marco.