Degeneration of retinal ganglion cells can cause irreversible vision loss. Pluripotent stem cells (PSCs) could, in theory, be used to replace lost ganglion cells. However, past attempts at injection of these cells have failed because the cells are not able to reach the retina.

Now, researchers have successfully demonstrated that disrupting an eye structure long suspected of blocking the growth and survival of transplanted nerve cells—the internal limiting basement membrane (ILM)—may help restore vision in people with optic nerve damage.

The work suggests that altering or removing the thin layer of tissue, which separates the light-sensing retinal tissue at the back of the eye from the gel-like vitreous fluid that fills the eye, was needed for the survival and migration of donor human PSC-derived retinal ganglion cells into the retina of mice, rats, and nonhuman primates. This technique could help transplanted retinal ganglion cells survive and grow in people with blinding optic nerve damage.

This work is published in Science Translational Medicine in the paper, “The internal limiting basement membrane inhibits functional engraftment of transplanted human retinal ganglion cells in vivo.”

Damage, or optic neuropathy, occurs when retinal ganglion cells die of disease, inflammation, or injury and stop carrying electrical signals to the brain. Common causes of damage include glaucoma, optic nerve inflammation (optic neuritis), and ischemic optic neuropathy (sudden loss of blood flow to the optic nerve).

Healthy, functional human retinal ganglion cells can be grown in a lab, but most die when transplanted, said Thomas Vincent Johnson III, MD, PhD, a professor of ophthalmology at the Johns Hopkins Wilmer Eye Institute. “Even when the retinal ganglion cells survive, they remain on the retina’s surface and do not migrate into the tissue or form the connections with other nerve cells necessary to detect light,” he noted.

Researchers have speculated that the internal limiting membrane, present in many vertebrates, including humans, may be causing transplant failures.

Starting with immunosuppressed rodents, the researchers injected lab-grown human retinal ganglion cells (hRGCs) into the vitreous humors of mice with an inborn gene mutation that caused an incomplete, patchy internal limiting membrane to form. They then injected the human retinal ganglion cells into a second group of mice treated with an enzyme solution known to partially digest the membrane without damaging the eye. Lastly, they injected a third, control group of mice treated with an inactive sterile solution. After two weeks, the team observed transplantation survival in 95% of eyes (45/50) with the inborn structural defect, 80% of enzymatically disrupted eyes (32/40), and 75% of control group eyes (12/16).

The researchers then traced where the surviving human retinal ganglion cells settled and grew in the mice, noting that a much greater percentage reached the retinal ganglion cell layer in mice born with a patchy internal limiting membrane and in those treated with the enzyme.

Capturing 3D images of the migrated cells, the researchers say they observed that 2% (plus or minus 0.6%) and 7.1% (plus or minus 1.6%) surviving cells in enzyme-treated and mutant eyes, respectively, matured to form dendrites. In contrast, migration and maturation only occurred in 0.01% plus or minus 0.01% of surviving control human retinal ganglion cells.

Conducting similar experiments in larger eyes and donated eye tissue replicated the group’s findings, establishing evidence that the inner limiting membrane is indeed a structural obstacle to neuron replacement, the researchers noted. They also established a surgical procedure for retinal ganglion cell transplantation that could be used in clinical trials, thus advancing potential methods for restoring vision in humans with optic neuropathy.

While the study’s results are promising, Johnson cautions that further work is still needed before their experimental findings can be applied to people. “We know our methods are effective, but we don’t know if completely removing the internal limiting membrane helps or harms the retinal ganglion cells in the long run,” he said. “It will likely take several years before our findings could become available as an experimental therapy, but the methods we developed will guide the field moving forward.”

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“Natural blood clots can be slow to form and mechanically fragile, which limits their ability to stop severe bleeding and can compromise healing,” said Jianyu Li, PhD, senior author and professor of mechanical engineering and Canada research chair in tissue repair and regeneration. “Our work shows that, when engineered appropriately, red blood cells can play a central structural role, enabling the design of stronger and more functional biomaterials.”

Senior and corresponding author Li, together with first author Shuaibing Jiang, PhD, reported on the development in Nature, in a paper titled “Engineering tough blood clots for rapid hemostasis and enhanced regeneration.” In their paper the team concluded, “Our strategy enables instantaneous clotting and markedly enhanced fracture resistance despite low structural polymer content, while preserving the intrinsic bioactivity of blood clots to enhance hemostasis and regeneration.”

Jiang, now a postdoctoral associate at Harvard Medical School, led the research during his PhD studies at McGill. Researchers at the University of British Columbia, the Medical College of Wisconsin, the University of Colorado Boulder, the University of Toronto and the research institute Versiti also contributed.

“Blood clots are pivotal for hemostasis and regeneration, but they are mechanically weak and form slowly, posing risks for life-threatening hemorrhage and limiting broader applications,” the authors wrote. “These limitations are attributed to complex coagulation cascades, abundant mechanically ineffective cells, and little structural polymers.”

Previous efforts to crosslink red blood cells (RBCs) have used chitosan, a polymer derived from crustacean shells, but these led to brittle clots, ruptured cells, and inconsistent clotting. In “click clotting,” the clot structure is fundamentally strengthened through a fast, bio-safe chemical reaction that connects proteins on the red blood cell surface, forming a solid gel in just five seconds. Because the “click” reaction doesn’t interfere with normal blood chemistry, it can work alongside the body’s natural clotting process. As a result, the artificial cell‑based gel, called a “cytogel,” can be added to whole blood, where it becomes embedded within the body’s own fibrin clot.

Li added, “The technology enables both autologous clots (using the patient’s own blood) and allogeneic clots (using type-matched donor blood). Autologous clots can be prepared in approximately 20 minutes, while allogeneic clots can be prepared within about 10 minutes. Given typical clinical time constraints, this approach has strong potential for in-patient emergency care, wound management and related settings.”

The team confirmed their results through in vitro testing, as well as through tests in rodents. “In vivo studies demonstrate that EBCs can rapidly halt hemorrhage, promote tissue regeneration, mitigate inflammation and foreign body reactions, and prevent postoperative adhesion,” the authors stated. Of particular note was effective healing and regeneration observed in the injured liver, with performance exceeding that of a clinically used product tested also tested as part of the study. “Compared with previously reported biomaterials for liver regeneration, EBC demonstrated milder inflammation and more efficient tissue regeneration,” the authors noted. Analyses showed minimal evidence of immune reactivity and no toxicity in major organs.

The researchers say that while further study is required before the cytogel can be used in clinical settings, the research establishes a foundation for its design and application.  “Overall, EBC, as a native scaffolding material, can promote tissue regeneration with minimal inflammation and foreign body responses, and prevent postoperative adhesions, outperforming the clinically used products,” the scientists concluded. “This work may motivate the development and translation of highly cellularized materials for bleeding control, wound management, tissue repair and regenerative medicine.”

“Engineered blood clots have strong potential for broad clinical use and could improve outcomes across many medical situations,” Li said.

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Researchers at the U.S. National Institute of Standards and Technology (NIST) and EMD Millipore put forward the idea, arguing that twins could make drug distribution, which is also characterized by thousands of interactions, more resilient and efficient.

Lead author Perawit Charoenwut, a logistics researcher at NIST’s systems integration division, tells GEN, “A digital twin could be extremely helpful in all phases of the biopharmaceutical supply chain. Starting from demand planning triggered by global events such as pandemics, regional disease outbreaks, aging demographics, etc., through to being able to provide visibility on capacity requirements and limitations.”

In silico models could also provide solutions to disruption by identifying alternative supply options, such as distribution centers or regional inventories, in less time, Charoenwut says.

“Digital twins could also be helpful in evaluating different suppliers by running simulations on their potential performance, based on different demand scenarios versus their individual capacities and capabilities,” he continues.

Standards

In theory, digital twins are a good option for supply chain modeling and management. In practice, however, firms interested in the approach will need to overcome some technical challenges.

For example, one major hurdle is the lack of data standardization, according to study co-author Boonserm Kulvatunyou, PhD, a computer engineer at NIST. “Supply chain digital twins require data from across organizations and third-party sources,” he tells GEN. “The lack of industry standards creates challenges in obtaining all the necessary data.”

With this in mind, the NIST’s Industrial Ontology Foundry (IOF) is working with the National Innovation Institute for Manufacturing Biopharmaceuticals (NIIMBL) to develop open-source ontology and schema standards for connecting data.

Kulvatunyou says, “The aim is to provide a semantic foundation for connecting data and knowledge across the manufacturing and supply chain operations.

“Further work is being conducted to cover broader materials, processes, and quality data,” he says. “We would like to invite industry and academia to join this effort and benefit from these new standards.”

Industry interest

Biopharma firms interested in digital supply chains will also need to establish a solid data infrastructure, according to Charoenwut, who says companies should start small and pace themselves.

“We think that biopharma companies do believe that digital twins could make a significant difference in their supply chain efficiency and resiliency. Many of them are probably building prototypes and proofs-of-concept to demonstrate the value and potential benefits, but then soon realize the digital data foundation gaps that need to be addressed in parallel in order to fully adopt this technology.

“As digital twins can vary in detail and complexity, companies should strategize digital twin adoption by starting with lower-complexity cases based on available digital data and progressively moving up the scale to gain greater precision and new capabilities. In other words, the implementation of digital twins should be viewed as an evolution rather than a breakthrough,” he says.

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These nanoscale carriers are naturally designed for transport. They can survive digestion, move into circulation, and distribute cargo throughout the body, with studies suggesting they may even reach the brain during early development. Researchers have shown that these vesicles can influence central nervous system communication, particularly through interactions with microglia, which are crucial to the brain’s immune cells. The ability of milk exosomes to carry microRNAs and regulate epigenetic pathways, including DNA methyltransferase 1 (DNMT1), points to a sophisticated biological delivery system that the industry is now learning to harness.

That potential is especially compelling in drug manufacturing, where delivery often determines whether a therapy succeeds or fails. Traditional nanoparticles can trigger toxicity, instability, or poor absorption. Milk exosomes offer a more elegant alternative: they are biocompatible, naturally abundant, and scalable for pharmaceutical development.

Huiming Tu, MD, a researcher and clinician in the department of gastroenterology at the Affiliated Hospital of Jiangnan University in Wuxi, China, and his colleagues recently demonstrated this with ulcerative colitis. Their team developed an oral delivery platform called mEXOs@TOF, which loads the pan-JAK inhibitor tofacitinib into milk-derived exosomes. The resulting formulation showed strong pharmaceutical performance, including consistent particle size, high drug-loading efficiency, and strong stability during delivery.

More importantly, the therapy improved anti-inflammatory outcomes through multiple mechanisms. It lowered inflammatory mediators such as IL-6, IFN-γ, and nitric oxide, while increasing anti-inflammatory IL-10. It also reduced oxidative stress and suppressed activation of the JAK-STAT3 signaling pathway. In both laboratory and animal studies, the system delivered strong therapeutic benefits without detectable toxicity—an ideal benchmark for translational bioprocessing.

Cancer therapy is seeing similar innovation. Min Suk Shim, PhD, professor of nano-bioengineering at Incheon National University in the Republic of Korea, and colleagues focused on sonodynamic therapy, in which ultrasound activates a sensitizing drug to destroy tumors. Their challenge was improving intracellular delivery of chlorin e6 (Ce6), a common sonosensitizer.

The team engineered glutathione-responsive milk exosomes by incorporating a diselenide bond-bearing fatty amine derivative. This allowed the vesicles to remain stable during circulation but release Ce6 inside breast cancer cells, where glutathione concentrations are higher. Once ultrasound was applied, reactive oxygen species production increased dramatically, leading to significant cancer cell death in MCF-7 breast cancer models. The work shows how responsive bioprocess design can turn natural vesicles into precision-triggered therapeutics.

Meanwhile, scientists from Hong Kong and China have reviewed the broader landscape of milk exosomes in breast cancer treatment. Beyond acting as delivery vehicles for drugs like doxorubicin, paclitaxel, and 5-fluorouracil, milk exosomes may also have direct anti-tumor effects. They can promote apoptosis, interrupt the cell cycle, and regulate pathways such as NF-κB and STAT3. Combined with plant-derived compounds like curcumin and resveratrol, they form hybrid nanoparticles with enhanced therapeutic power.

For bioprocessing, the message is clear: milk exosomes are no longer a niche curiosity. They represent a scalable, safe, and highly adaptable platform for next-generation therapeutics—one that begins with biology’s oldest delivery system and may define medicine’s next one.

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Hagen Cramer, PhD, QurAlis’s CTO, thinks synthesizing oligonucleotides using enzymes could be more sustainable than traditional solid-phase synthesis methods, but challenges remain for the industry.

“Solid-phase synthesis is convenient—you can have everything automated, it’s fast, and can be used for [many] types of therapeutics,” he says. “However, because it’s a solid-phase synthesis, you have to wash away the external reagents with lots of solvents, and that’s why the mass intensity is high.”

By contrast, manufacturing RNA and DNA using a process that happens in nature and is aqueous-based uses fewer materials in the production of any given mass of product, notes Cramer. However, creating a wide selection of enzymes to manufacture multiple products remains a challenge for the industry.

“Enzymatic synthesis]was explored a long time ago, but it went away because people couldn’t figure out the challenges,” he points out. “But there’s now a lot more money in the industry as we have approved drugs and, hence, it’s now being reinvestigated.”

Other challenges include using enzymatic techniques for manufacturing above the 100-g scale and also speeding up these techniques to be comparable with solid-phase synthesis.

“With solid-phase synthesis, if you have a 20-mer oligonucleotide, you might have to take 80 chemical steps, and you can be efficient and complete all of that in a day, but—with an enzymatic approach—it’s going to take much longer and the development time is also large,” explains Cramer, adding that clinical-stage companies making smaller volumes may want to stick with solid-phase synthesis. But, he continues, commercial-stage companies producing large volumes of product may want to investigate enzymatic approaches as they become available.

“At a certain stage, if you’re working at commercial stage already, you can plan ahead and I think the industry will move toward these new approaches starting post-market,” he says.

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The Adaptive Agent-Oriented System Control (AAOSC) framework developed by a team from the Technical University of Denmark (DTU) and SiC Systems addresses that challenge through a decentralized control layer. In it, “specialized autonomous agent ‘hives’ [are] coordinating digital twin enabled manufacturing infrastructure and real-time communications protocols.” The latter lets biomanufacturers integrate models, make learning-based inferences, and control process systems.

Four AAOSC case studies were discussed in a recent paper by Seyed Soheil Mansouri, PhD, professor at DTU and co-founder and CSO of SiC Systems and Christopher J. Savoie, PhD, co-founder and CEO of SiC Systems, and inventor of the agentic AI technology behind Siri. Those case studies “demonstrate AAOSO’s prowess [in] reducing deviating durations, averting shutdowns in severe fault scenarios, and boosting efficiency through virtual quantum and classical sensing and decentralized reasoning, all while aligning with regulatory imperatives…”

Despite its capabilities in monitoring process, identifying discrepancies, and recommending solutions, agentic AI “is not yet fully ready for complete, independent control in biopharmaceutical manufacturing,” Mansouri tells GEN. “Any AI that directly affects medicine quality still needs strong human oversight and full approval. We are getting closer, but full integration requires official [regulatory] clearance.”

The AAOSC framework that Mansouri and colleagues built may be unique in the industry. It isn’t all-knowing and “God-like,” he points out. Instead, “our methods are grounded in physics, chemistry, and biology within an agent ‘hive’—an orchestration of rule-based, mathematically informed agents. So, AAOSC is, foundationally, a different philosophy of building AI [in which] humans are in control.”

First, run in shadow mode

To introduce agentic AI, Mansouri advises starting gradually. “Run the AI alongside your current control systems in shadow mode—it watches everything and gives recommendations, but doesn’t make any actual changes without human oversight. This lets the teams learn how it works without any risks to production. Once confident, you can slowly expand its role while always keeping humans in final control.”

Both the FDA and EMA require systems that are fixed rather than continuously learning, he points out, and that can complicate adoption. To minimize the potential for regulatory issues that may arise by integrating AI into manufacturing processes, “work closely with your quality and regulatory teams from the beginning.

“Always maintain clear human responsibility, so no one is left wondering who is accountable if something goes wrong. Strong cybersecurity is essential,” Mansouri adds, “because these AI agents connect and talk to each other.” Therefore, “Start small, test thoroughly, and talk to regulators early.”

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The researchers examined approximately 5.5 million neurons in more than 300 individual mice using single-cell sequencing and spatial transcriptomics. Results showed that neurons are organized into tight, overlapping, horizontal stripes from the top to the bottom of the nose based on the type of smell receptor expressed. This highly organized receptor map was consistent across mouse models and mirrored the organization of smell maps in the brain. Similar maps have been observed in vision, hearing, and touch.

Notably, the olfactory map was informed by a gradient of retinoic acid in the nose, which allowed each neuron to express the correct type of smell receptor based on its spatial location.  

“Our results bring order to a system that was previously thought to lack order, which changes conceptually how we think this works,” said Sandeep (Robert) Datta, PhD, professor of neurobiology at HMS and senior author and corresponding author of the study. “We show that development can achieve this feat of organizing a thousand different smell receptors into an incredibly precise map that’s consistent across animals.” 

The authors also found that the receptor map in the nose matches up with smell maps in the olfactory bulb of the brain, shedding insight into how information moves from the nose to the brain. 

While sensory maps that describe how receptors in the eye, ear, and skin are organized to capture and interpret auditory, visual, and touch information, mapping olfactory receptors has been a longstanding challenge due to high receptor diversity. As an example, mice have approximately 20 million olfactory neurons that express more than a thousand types of smell receptors, compared with only three main types of visual receptors for color vision. Each type of smell receptor detects a unique subset of odor molecules. 

The team is also studying smell receptors in human tissue to understand to what degree the smell map is consistent across species to inform treatments, such as stem cell therapies and loss of smell and its consequences, such as an increased risk of depression. 

“Smell has a really profound and pervasive effect on human health, so restoring it is not just for pleasure and safety but also for psychological well-being,” Datta said. “Without understanding this map, we’re doomed to fail in developing new treatments.” 

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The collaboration brings together the circVec platform and TraffikGene’s peptide amphiphile carrier system. The combination of these complementary technologies is designed to enable high-throughput screening of circVec delivery with enhanced tissue targeting. The aim is to identify optimized formulations capable of prolonged, efficient, and targeted delivery of non-viral circVec vectors into specific cell and tissue types.

“Combining TraffikGene’s carrier discovery capabilities with Circio’s innovative circular RNA scaffolds opens a compelling new avenue for the development of next-generation nucleic acid medicines,” said Javier Montenegro, PhD, principal investigator of the TraffikGene project at USC.

The collaboration will involve three stages: initial screening of peptide carriers combined with non-viral circVec vectors in vitro, physicochemical optimization of lead formulations, and in vivo evaluation in mouse models to assess expression kinetics, biodistribution, and delivery efficacy.

“Cutting edge delivery technologies are essential to reach new tissues in an efficient and safe manner,” added Thomas B Hansen, PhD, CTO of Circio. “This collaboration is an excellent opportunity to evaluate whether TraffikGene’s non-viral carriers can unlock the full potential of Circio’s circVec platform. In addition, it will allow us to evaluate circular RNA expression dynamics and tissue-specific performance in more detail, which are key research areas to identify new therapeutic applications for the circVec platform.”

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The work comes from researchers at the Icahn School of Medicine at Mount Sinai, who report that non‑immune cells—including muscle fibers and hepatocytes—play a decisive role in determining mRNA vaccine potency. Their paper, “mRNA vaccine immunity is enhanced by hepatocyte detargeting and not dependent on dendritic cell expression,” was published today. The findings overturn a long‑held assumption that mRNA vaccines must deliver their payload to dendritic cells to prime strong T‑cell responses.

“This study fundamentally changes how we think mRNA vaccines work,” said senior author Brian D. Brown, PhD, director of the Icahn Genomics Institute. “For years, the field has assumed that getting the mRNA into dendritic cells, the immune cells that activate T cells, was essential. We show that’s not the case. These cells are still important, but mRNA delivery to them is not required.”

To dissect how different cell types influence immunity, the team used a microRNA‑based technology developed in Brown’s lab that allows researchers to “turn off” mRNA expression in specific cell populations. By incorporating short microRNA target sequences into the mRNA, they selectively silenced expression in dendritic cells, hepatocytes, or muscle cells while leaving other tissues unaffected.

The results were striking. Silencing mRNA expression in dendritic cells did not impair T‑cell priming, including for SARS‑CoV‑2 antigens, suggesting that cross‑presentation by other cell types is sufficient to initiate immunity. “This was unexpected,” said Brown. “It tells us that other cells are producing the vaccine antigen and handing it off to the immune system.” In contrast, turning off expression in muscle fibers weakened the immune response, while turning off expression in hepatocytes tripled it.

“We found that hepatocytes actively dampen the immune response to mRNA vaccines,” said Sophia Siu, an MD/PhD student and co‑lead author. “This is notable because hepatocytes can take up a lot of mRNA, particularly when it’s injected intravenously. For vaccines, we discovered that we don’t want expression in hepatocytes. However, for mRNA therapeutics, hepatocyte expression can be beneficial because it may help prevent immunity to the mRNA-encoded protein.”

“In mice bearing tumor-associated antigen (TAA)-expressing lymphoma cells, miRT-mediated hepatocyte-silenced TAA mRNA vaccine enhanced immune response and reduced tumor burden,” wrote the authors. The approach also reduced hepatocyte death when mRNA was used to boost pre‑existing T cells, an important consideration for gene‑editing and CAR T–related applications.

“These results show that we can make mRNA cancer vaccines more effective simply by controlling where the mRNA‑encoded antigen is expressed,” said Joshua D. Brody, MD, director of the Lymphoma Immunotherapy Program at the Mount Sinai Tisch Cancer Center. “It’s a new lever for improving immunotherapy.”

Beyond oncology, the findings could influence the design of mRNA‑based vaccines for infectious diseases and therapeutics for autoimmune and genetic disorders. By tuning expression in specific cell types, researchers can amplify or dampen immune responses as needed.

“mRNA technology is transformative for medicine,” Brown said. “Our work provides a new set of design rules for mRNA vaccines and therapeutics. As this technology continues to evolve, understanding and controlling where mRNA is expressed will be critical.”

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“As tumors progress, cancer cells leave the original site and spread or metastasize to other organs where they seed new tumors,” said Xiang Zhang, PhD, William T. Butler, MD, Endowed Chair for Distinguished Faculty, professor of molecular and cellular biology, and director of the Lester and Sue Smith Breast Center at Baylor. “Our lab is interested in better understanding what cellular and molecular features support metastasis as these could guide the development of therapies to prevent, slow down, or eliminate them. In the current study, we first developed a new method to identify the makeup of metastatic niches.”

Zhang, also a member of Baylor’s Dan L Duncan Comprehensive Cancer Center, is senior and corresponding author of the team’s published paper in Cell, titled “Unbiased niche labeling maps immune-excluded niche in bone metastasis.”

During metastasis, cancer cells interact constantly with other normal cells in the body, and these interactions affect cell behavior, fate, and even response to therapies. “Numerous previous studies have elucidated the roles of specific microenvironment niches (i.e., cells that are immediately adjacent to cancer cells) in the progression of metastasis,” the authors wrote.

For their newly reported study the team developed the SAMENT technology. “Our method allowed us to identify specific cells encountered by cancer cells during metastasis,” said co-first author Fengshuo Liu, graduate student in the Cancer and Cell Biology Program working in the Zhang lab. “The method, called Sortase A–Based Microenvironment Niche Tagging (SAMENT), selectively labels normal cells that come into direct contact with cancer cells.”

The authors further explained, “By combining SrtA and synthetic ligand-receptor binding, we aim to label any cells that are physically encountered by cancer cells.”

The investigators’ tests using SAMENT revealed that pro-metastatic microenvironments of multiple cancer models in all the organs studied, including bone, lung, liver, and brain, shared common features, including an abundance of macrophage immune cells and shortage or absence of immune T cells, which typically help fight tumors. “Among all cell types, macrophages occur most frequently surrounding disseminated cancer cells and appear to be phenotypically re-programmed upon interaction with metastases,” they wrote.

Liu added, “However, bone metastases stood out. We were surprised to find that macrophages surrounding cancer cells in bone metastases activated a protein called estrogen receptor alpha (ERα). This protein is best known for its role in hormone-responsive breast cancer but is much less studied in macrophages or other immune cells.” The team added, “It also plays an important role in many other cell types, including macrophages, T cells, osteoblasts, and osteoclasts.”

The study showed that macrophages with active ERα signaling were not detected in normal bone or in primary tumors in other tissues. ERα-active macrophages were also present in human bone metastasis samples from patients with breast, lung and kidney cancers—including male patients. This showed that this finding is not limited to one cancer type or to women.

The researchers also investigated how cancer cells turned macrophages, which would typically fight cancer, into their allies. Cancer cells deliver small molecules called fatty acids (FAs) to macrophages, likely through tiny particles known as extracellular vesicles (EVs). These fatty acids activate a metabolic pathway in macrophages that turns on ERα signaling. “Taken together, our data indicate that ERα expression in macrophages is driven by cancer cell-derived FAs through paracrine interaction mediated by EVs,” they wrote.

Once ERα is active, macrophages become immunosuppressive—instead of helping the immune system attack cancer, they form a barrier that physically and chemically blocks T cells from reaching tumor cells. ERα-active macrophages act as bodyguards for metastatic cancer in bone.

“To test whether ERα in macrophages can drive bone metastasis, we genetically removed the ERα gene specifically from macrophages in mice,” Liu continued. “As a result, cancer cells were far less able to colonize bone in multiple cancer models. Tumors grew more slowly, and metastases in other organs that often arise from bone tumors were also reduced. Importantly, removing ERα from macrophages did not disrupt normal bone health—bone structure and remodeling remained intact.” In their paper the scientists stated, “Taken together, our results strongly support the hypothesis that ERα in macrophages plays an important role in bone colonization.”

“When macrophage ERα was genetically removed or when mice were treated with fulvestrant, an FDA-approved cancer drug that degrades estrogen receptors, T cells were able to enter metastatic lesions in bone and kill tumor cells,” Zhang said. “Our findings support conducting future human clinical trials to assess the value of estrogen-blocking therapies combined with other therapies to treat bone metastases across multiple cancer types, in both women and men.”

The authors added, “Furthermore, as shown in the final set of experiments, inhibition of ERα in macrophages may not be effective by itself but could synergize with immunotherapies because it facilitates T cell infiltration into static lesions.” The team acknowledged that they didn’t see any synergy between Erαknockout in macrophages and anti-PD1 treatment. However, they noted, “… it is still worth exploring the combinatory effects with other immunotherapies. Therefore, our findings may warrant future clinical trials on combined endocrine and immunotherapies on patients with bone metastases, and this combination may be extended to other cancer types and to patients of both genders.”

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