The study, “Endothelial TDP-43 Depletion Disrupts Core Blood-Brain Barrier Pathways in Neurodegeneration,” was published on March 14, 2025. The lead author, Omar Moustafa Fathy, an MD/Ph.D. candidate at the Center for Vascular Biology at UConn School of Medicine, conducted the research in the laboratory of senior author Dr. Patrick A. Murphy, associate professor and newly appointed interim director of the Center for Vascular Biology. The study was carried out in collaboration with Dr. Riqiang Yan, a leading expert in Alzheimer’s disease and neurodegeneration research.

This work provides a novel and significant exploration of how vascular dysfunction contributes to neurodegenerative diseases, exemplifying the powerful collaboration between the Center for Vascular Biology and the Department of Neuroscience. While clinical evidence has long suggested that blood-brain barrier (BBB) dysfunction plays a role in neurodegeneration, the specific contribution of endothelial cells remained unclear. The BBB serves as a critical protective barrier, shielding the brain from circulating factors that could cause inflammation and dysfunction. Though multiple cell types contribute to its function, endothelial cells — the inner lining of blood vessels — are its principal component.

“It is often said in the field that ‘we are only as old as our arteries’. Across diseases we are learning the importance of the endothelium. I had no doubt the same would be true in neurodegeneration, but seeing what these cells were doing was a critical first step,” says Murphy.

Omar, Murphy, and their team tackled a key challenge: endothelial cells are rare and difficult to isolate from tissues, making it even harder to analyze the molecular pathways involved in neurodegeneration.

To overcome this, they developed an innovative approach to enrich these cells from frozen tissues stored in a large NIH-sponsored biobank. They then applied inCITE-seq, a cutting-edge method that enables direct measurement of protein-level signaling responses in single cells — marking its first-ever use in human tissues.

This breakthrough led to a striking discovery: endothelial cells from three different neurodegenerative diseases — Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD) — shared fundamental similarities that set them apart from the endothelium in healthy aging. A key finding was the depletion of TDP-43, an RNA-binding protein genetically linked to ALS-FTD and commonly disrupted in AD. Until now, research has focused primarily on neurons, but this study highlights a previously unrecognized dysfunction in endothelial cells.

“It’s easy to think of blood vessels as passive pipelines, but our findings challenge that view,” says Omar. “Across multiple neurodegenerative diseases, we see strikingly similar vascular changes, suggesting that the vasculature isn’t just collateral damage — it’s actively shaping disease progression. Recognizing these commonalities opens the door to new therapeutic possibilities that target the vasculature itself.”

The research team believes this newly identified subset of endothelial cells could provide a roadmap to targeting this endothelial disfunction to stave off disease, and also to develop new biomarkers from the blood of patients with disease.

Funding was provided by startup funds from the UConn School of Medicine and Department of Cell Biology, Center for Vascular Biology and Calhoun Cardiology Center, American Heart Association Innovative Project Award 19IPLOI34770151 (to P.A.M.); NIH National Heart, Lung, and Blood Institute Grants K99/R00-HL125727 and RF1-NS117449 (to P.A.M); American Heart Association Predoctoral award 23PRE1027078 (to O.M.F.O.) R01-AG046929 and R01-NS074256 (to R.Y.) and NIH GM135592 (to B.H.).

Combatting the “undruggable” RAS genes

Patients with pancreatic cancer have an overall poor prognosis: in most patients, the disease has already spread at the time of diagnosis, resulting in limited treatment options. Nearly 90 percent of pancreatic cancers are driven by KRAS mutations, the most common cancer-causing gene mutation across cancer types, which researchers long considered “undruggable.” In 2021, the first KRAS inhibitor was approved to treat non-small cell lung cancer with KRAS G12C mutations, but with longer follow-up, it has become clear that KRAS-mutant cancers can quickly evolve to resist therapies targeted at one specific form of the gene mutation.

“We’ve been excited by the prospect of RAS inhibition for pancreatic cancer, which remains one of the deadliest and most difficult forms of cancer to treat,” said co-corresponding senior author Ben Stanger, MD, PhD, the Hanna Wise Professor in Cancer Research and director of the Penn Pancreatic Cancer Research Center. “While the first wave of KRAS inhibitors have had limited impact in cancer care, this research shows that newer RAS inhibition tools may have an immune stimulatory effect, making them ideal to pair with immunotherapy for longer and better treatment response.”

Previous research led by Stanger and Robert Vonderheide, MD, DPhil, director of the Abramson Cancer Center, who is also co-corresponding author on this study, showed that a small molecule inhibitor specifically targeting KRAS G12D, the form of the mutation more commonly found in pancreatic cancer, stimulated the immune system while shrinking tumors or stopping cancer growth in preclinical mouse models of pancreatic cancer.

A new type of RAS inhibitor

In this study, the researchers used RAS(ON) multi-selective inhibitors, the investigational agent daraxonrasib (RMC-6236) and the preclinical tool compound RMC-7977 (both discovered by Revolution Medicines, whose scientists contributed to the study). These inhibitors use a different mechanism of action than most other KRAS inhibitors (including that in the previous study) to target the active or ON-state of multiple forms of RAS mutations.

“The benefit of this ‘multi-selective’ approach is that the inhibitors are designed to inhibit multiple RAS mutations, so if the cancer mutates, and another type of RAS mutation emerges, the treatment may not necessarily stop working,” Vonderheide explained.

The research team found that not only was RAS(ON) multi-selective inhibition effective in preclinical pancreatic cancer models, but it was even more effective when combined with immunotherapy. Using the combination approach, all mouse models had tumor shrinkage and half had a complete response, meaning the tumor was eliminated.

The research team used a Penn-developed immunocompetent model considered the gold standard worldwide for assessing potential therapies for pancreatic ductal adenocarcinoma. This model allows the tumor to spontaneously evolve after implantation, making it possible to discern the drug’s impact on the surrounding tumor microenvironment. The research team found that RAS(ON) multi-selective inhibition reshaped the tumor microenvironment by bringing in more T cells and other immune cells, making the tumor particularly receptive to immunotherapy.

Next steps and clinical trial information

Daraxonrasib (RMC-6236) is already being tested in clinical trials across the United States. A clinical trial testing RAS(ON) inhibitors with other anticancer agents in certain patients with gastrointestinal solid tumors is now open at several sites across the country, including at Penn Medicine. Click here for more information about the study.

“We’re hopeful that we’re starting to crack the code on immunotherapy and RAS therapy for pancreatic cancer,” Vonderheide said. “After decades of limited progress, it’s encouraging to see new treatment approaches making their way into the clinic for patients.”

The study was supported by Revolution Medicines, the National Institutes of Health (R01CA252225, R01CA276512, P30DK050306, P30CA016520) the Department of Defense (W81XWH2210730), the Molecular Pathology and Imaging Core, A Love for Life, the Basser Center for BRCA, and the Penn Pancreatic Cancer Research Center.

Information for patients interested in joining a clinical trial: visit Penn Medicine’s Abramson Cancer Center Clinical Trial Information Service online or call 1-855-216-0098 to speak to a clinical trial navigator.

Editor’s note: Vonderheide is an inventor on patents relating to cancer cellular immunotherapy and KRAS immune epitopes.

In a recent study reported in the Feb. 15 issue of Nature Communications, scientists from The Jackson Laboratory (JAX) and UConn Health not only show how cancer hijacks this tightly regulated splicing and rearranging of RNA but also introduce a potential therapeutic strategy that could slow or even shrink aggressive and hard-to-treat tumors. This discovery could transform how we treat aggressive cancers, such as triple-negative breast cancer and certain brain tumors, where current treatment options are limited.

At the heart of this work, led by Olga Anczuków, an associate professor at JAX and co-program leader at the NCI-designated JAX Cancer Center, are tiny genetic elements called poison exons, nature’s own “off switch” for protein production. When these exons are included in an RNA message, they trigger its destruction before a protein can be made — preventing harmful cellular activity. In healthy cells, poison exons regulate the levels of key proteins, keeping the genetic machinery in check. But in cancer, this safety mechanism often fails.

Anczuków and her team, including Nathan Leclair, an MD/PhD graduate student at UConn Health and The Jackson Laboratory who spearheaded the research, and Mattia Brugiolo, a staff researcher who contributed his expertise, discovered that cancer cells suppress poison exon activity in a critical gene called TRA2β. As such, levels of TRA2β protein increase inside cancer cells, causing tumor proliferation.

Furthermore, the team found a correlation between levels of poison exons and patient outcomes. “We’ve shown for the first time that low levels of poison exon inclusion in the TRA2β gene are associated with poor outcomes in many different cancer types, and especially in aggressive and difficult-to-treat cancers,” said Anczuków. These include breast cancer, brain tumors, ovarian cancers, skin cancers, leukemias, and colorectal cancers, Anczuków explained.

Anczuków, Leclair, and Brugiolo then went on to see if they could increase the inclusion of the poison exon in the TRA2β gene and reactivate the kill switch. They found their answer in antisense oligonucleotides (ASOs) — synthetic RNA fragments that can be designed to increase poison exon inclusion in specific ways. When introduced into cancer cells, ASOs effectively flipped the genetic switch, restoring the body’s natural ability to degrade excess TRA2β RNA and inhibit tumor progression.

“We found that ASOs can rapidly boost poison exon inclusion, essentially tricking the cancer cell into turning off its own growth signals,” said Leclair. “These poison exons work like a rheostat, quickly adjusting protein levels — and that could make ASOs a highly precise and effective therapy for aggressive cancers.”

Interestingly, when researchers completely removed TRA2β proteins using CRISPR gene editing, tumors continued to grow — suggesting that targeting the RNA rather than the protein could be a more effective approach. “This tells us that poison-exon-containing RNA doesn’t just silence TRA2β,” explained Anczuków. “It likely sequesters other RNA-binding proteins, creating an even more toxic environment for cancer cells.”

Further studies will refine ASO-based therapies and explore their delivery to tumors. However, preliminary data suggest that ASOs are highly specific and do not interfere with normal cellular function, making them promising candidates for future cancer treatments. This research was supported by the National Institutes of Health and the NCI-designated JAX Cancer Center.