The research team, led by Suzanne M. de la Monte of the Departments of Pathology and Laboratory Medicine, Neurology, Neurosurgery, and Medicine at Rhode Island Hospital, together with Ming Tong, obtained six-millimeter cores of the anterior cerebellar vermis from the New South Wales Brain Tissue Research Centre in Sydney, Australia. The samples came from six male donors with alcohol use disorder and six matched male controls, all between fifty and seventy years of age. The groups were closely matched for age, years of drinking, postmortem interval, and brain pH, but differed dramatically in lifetime alcohol exposure: the AUD donors had consumed an average of roughly 2,784 kilograms of alcohol over their lifetimes, compared with about 42 kilograms in the controls. Consistent with the toxic burden, the AUD brains weighed significantly less, averaging 1,335 grams against 1,505 grams in controls.

What makes this study technically distinctive is its methodological breadth. Rather than relying on a single assay, the investigators processed the fresh frozen tissue through parallel pipelines: duplex enzyme-linked immunosorbent assays to quantify oligodendrocyte and astrocyte proteins, magnetic bead-based multiplex panels to measure twenty-one cytokines, chemokines, and trophic factors, seven-plex assays for total and phosphorylated Akt pathway signaling proteins, and custom QuantiGene 2.0 multiplex RNA hybridization panels to quantify messenger RNA transcripts for glial genes, the insulin and insulin-like growth factor system, and the Notch pathway. Every assay was run in triplicate under code, normalized to internal reference standards, and analyzed with two-way analysis of variance and post hoc multiple comparison tests.

The oligodendrocyte findings were striking. Protein analysis revealed significantly elevated levels of CNPase, an enzyme associated with immature myelin, and myelin oligodendrocyte glycoprotein, or MOG, a marker of mature oligodendrocytes, in the AUD cerebellar white matter. The RNA analysis was even more revealing, detecting broad upregulation of immature and mature myelin genes alike: KLK6, a serine protease linked to myelin degradation, along with CNPase, myelin basic protein, proteolipid protein, and MOG were all significantly increased. At first glance, elevated myelin gene expression might seem like good news, but the authors interpret it as a sign of dysfunction rather than health. In experimental models of alcohol-related brain damage, similar upregulation appears in subacute stages of injury, before the later collapse of myelin gene expression. The pattern suggests oligodendrocytes struggling to compensate for damaged myelin, much like a factory running overtime to replace a product that keeps failing.

The elevation of KLK6 is particularly telling. Previous work has shown that inhibiting this protease in oligodendrocytes is associated with cellular maturation and increased myelin thickness and volume. Its upregulation in the AUD samples, the authors argue, corresponds with a failure of oligodendrocytes to fully mature, which would compromise the synthesis and maintenance of the myelin sheaths that give white matter its integrity. This interpretation dovetails with earlier lipidomic mass spectrometry studies showing altered myelin lipid composition in alcohol-related brain damage, and with diffusion tensor imaging studies demonstrating disruption of white matter microstructural integrity in living patients with alcohol use disorder.

Beneath these cellular changes, the study uncovered disruptions in two master signaling systems. The first is the insulin and insulin-like growth factor pathway, which supports cell growth, survival, and energy metabolism throughout the brain. While mRNA levels of insulin pathway genes showed only modest, statistically insignificant shifts, the protein-level analysis told a sharper story: total Akt, a central kinase in the pathway, was significantly reduced, as was GSK-3β and its serine-9 phosphorylated form. These reductions suggest impaired signaling through the PI3K-Akt axis, which experimental models of chronic ethanol exposure have repeatedly implicated in neurodegeneration. The second system is the Notch pathway, a developmental signaling network that also regulates oligodendrocyte myelin synthesis and maintenance in the adult brain. Here the RNA assays revealed significant reductions in ASPH, aspartyl-asparaginyl-beta-hydroxylase, and HES1, a downstream Notch transcriptional target. ASPH is the enzyme that hydroxylates Notch receptors’ EGF-like domains, enabling the cleavage and nuclear translocation that activates the pathway. Its suppression, the authors propose, would throttle Notch signaling and thereby cripple the oligodendrocyte functions needed to sustain central nervous system myelin.

Perhaps the most surprising result concerns neuroinflammation, long considered a primary driver of alcohol-related brain damage. The comprehensive cytokine and chemokine survey found that among twenty-one inflammatory mediators measured, only one, the pro-inflammatory cytokine IL-16, differed significantly between groups, and it was reduced, not elevated, in the AUD tissue. IL-16, a chemoattractant for CD4-positive T cells that has been implicated in inflammatory demyelinating diseases, was also the most abundantly expressed inflammatory factor in the cerebellar samples. The authors note that these findings contrast with studies linking increased neuroinflammation to short-term, binge, or developmental alcohol exposures, but align with other experimental data showing that chronic ethanol consumption can suppress immune and cytokine-mediated responses. On balance, the results do not support persistent chronic neuroinflammation as the prime mediator of white matter degeneration in this cohort.

One trophic factor did stand out: hepatocyte growth factor, or HGF, was significantly reduced in the AUD cerebellum. HGF plays a key role in preventing neuronal death and promoting cell survival, and its loss corresponds with the neuronal loss observed in the cerebellar cortex in alcohol-related brain damage. Given HGF’s pro-angiogenic and anti-inflammatory effects, its reduction may also bear on the blood-brain barrier disruption documented in this condition. The other growth factors measured, including nerve growth factor, vascular endothelial growth factor, stem cell factor, fibroblast growth factor, and stromal cell-derived factor, showed no significant AUD-related changes.

The study has clear limitations that the authors acknowledge candidly. Six brains per group is a modest sample, constrained by the scarcity of donors with uncomplicated alcohol-related brain damage free of other substance use disorders. All donors were male, reflecting the male predominance of heavy drinking in Australia, and the analysis captured only the endpoint of disease rather than its progression. The authors call for future work examining earlier timepoints and including donors with periods of abstinence, which would help assess whether the cerebellar white matter pathology is reversible. Encouragingly, prior neuroimaging studies have shown that cerebellar atrophy can be partially reversed with abstinence, making the identification of actionable disease stages clinically meaningful.

The translational horizon is perhaps the most exciting aspect of the work. Because oligodendrocytes and other brain cells release cell-type-specific membrane vesicles called exosomes into the bloodstream, the authors propose that the molecular signatures identified here could eventually be detected and monitored non-invasively through liquid biopsy approaches, analyzing exosomes isolated from peripheral blood. Such a test could allow clinicians to track alcohol-related oligodendrocyte pathology in living patients, stage the disease, and evaluate whether interventions, from abstinence to potential therapies targeting insulin/IGF-Akt signaling or Notch networks, are working. For a disorder that is among the most common and preventable causes of cerebellar degeneration worldwide, moving diagnosis from the autopsy table to the blood draw would represent a genuine leap forward in the fight against alcohol-related brain damage.

Subject of Research: Molecular mechanisms of alcohol-related cerebellar white matter degeneration in humans

Article Title: Molecular and biochemical pathologies in human alcohol-related cerebellar white matter degeneration

Article References: Molecular and biochemical pathologies in human alcohol-related cerebellar white matter degeneration. (n.d.). https://doi.org/10.3389/adar.2025.15342

Image Credits: AI Generated

DOI: 10.3389/adar.2025.15342

Keywords: alcohol use disorder, cerebellum, white matter, oligodendrocytes, myelin, insulin/IGF signaling, Akt, GSK-3β, Notch pathway, ASPH, neuroinflammation, postmortem brain tissue

Hepatocellular carcinoma, the most common primary liver cancer, remains one of the world’s deadliest malignancies. It is the third leading cause of cancer-related death globally, and although viral hepatitis, alcohol consumption, aflatoxin exposure and poor diet all contribute to its development, the clinical picture is dominated by a single grim statistic: most patients are diagnosed at an advanced stage, when surgical options such as resection, transplantation or ablation are no longer viable. Approved drug therapies for advanced disease, including multikinase inhibitors such as sorafenib, lenvatinib and cabozantinib, and antibody combinations built around agents like bevacizumab and atezolizumab, have extended survival only modestly. The field’s persistent hunger for molecules with new structures and new mechanisms is what makes the KGA-1002 story notable.

The compound’s origin lies in the chemistry of Artemisia, the genus that gave the world artemisinin. Sesquiterpenoid dimers, molecules in which two sesquiterpene units are joined, have repeatedly shown stronger antitumor activity than their monomeric parents, but their scarcity in plants has historically blocked serious drug development. The Kunming group sidestepped that bottleneck through biomimetic synthesis: using a Diels-Alder reaction, they assembled KGA-1002 from dehydrocostus lactone, an abundant natural sesquiterpenoid, on a ten-gram scale. The resulting dimer inhibited the proliferation of three hepatocellular carcinoma cell lines with IC50 values of 5.9, 6.9 and 6.3 micromolar against HepG2, Huh7 and SK-Hep-1 cells respectively, outperforming sorafenib and beating the parent monomer dehydrocostus lactone by roughly five- to seven-fold.

Identifying what a small molecule actually touches inside a cell is the hardest part of natural product pharmacology, and the team attacked it with a battery of orthogonal techniques. A drug affinity responsive target stability assay, which exploits the fact that ligand-bound proteins resist enzymatic digestion, flagged a protein band that survived pronase treatment only in the presence of KGA-1002. Mass spectrometry of that band yielded 49 candidate proteins, which transcriptomic profiling and bioinformatics narrowed to six. The decisive experiment was genetic: when the researchers silenced each candidate in liver cancer cells, only knockdown of GRP94, the endoplasmic reticulum-resident member of the heat shock protein 90 family, blunted the drug’s antiproliferative and anti-migratory effects. Surface plasmon resonance then measured direct binding, with a dissociation constant of 454 nanomolar, and a cellular thermal shift assay confirmed that KGA-1002 stabilizes GRP94 inside cells.

The structural detail goes further than most target-identification studies dare. KGA-1002 carries an alpha, beta-unsaturated carbonyl motif, a well-known covalent warhead, and molecular dynamics simulations showed that this group is essential for stabilizing the GRP94-ligand complex. Mass spectrometric sequencing of the treated protein revealed a peptide whose mass had increased by exactly the molecular weight of the drug, and secondary fragmentation localized the covalent bond to serine 106, a hydroxyl-bearing residue ideally positioned for nucleophilic attack on the unsaturated carbonyl. When the team mutated serine 106 to alanine, binding affinity collapsed from 522 nanomolar to 461 micromolar, a nearly thousand-fold loss. Critically, KGA-1002 did not stabilize the cytosolic family members HSP90alpha or HSP90beta, whose indiscriminate inhibition has doomed pan-HSP90 drugs in clinical trials. That isoform selectivity, aided by an additional contact with GRP94-specific asparagine 276, is arguably the compound’s most clinically relevant property.

With the target pinned down, the downstream biology fell into place. GRP94’s day job is folding, assembling and trafficking client proteins inside the endoplasmic reticulum, and its inhibition floods the ER lumen with misfolded polypeptides. Transcriptomic analysis of treated cells showed enrichment of ER-related pathways, upregulation of stress genes such as ERN1, ATF4 and DDIT3, and downregulation of ER trafficking genes. The canonical unfolded protein response sensors PERK and IRE1, normally held inactive by the chaperone BiP, were activated, driving expression and nuclear translocation of the death-promoting transcription factors XBP1 and CHOP. Because GRP94 also buffers calcium in the ER, the drug produced a dose-dependent rise in intracellular calcium, climbing to nearly 98 percent calcium-positive cells at 7.5 micromolar in both SK-Hep-1 and Huh7 lines. The unfolded protein response, in other words, was not a side effect but the engine of tumor killing.

The most novel mechanistic finding concerns AKT, the kinase at the heart of the PI3K survival pathway. KGA-1002 lowered AKT protein levels without touching its mRNA, and cycloheximide chase experiments showed the drug accelerating AKT degradation; proteasome and lysosome inhibitors each partially rescued the protein, implicating both disposal routes. The explanation proved to be a chaperone-client relationship: GRP94 physically holds AKT, and pulldown assays demonstrated that KGA-1002 disrupts that interaction, both in cell lysates and with purified proteins. Destabilized AKT could no longer phosphorylate SKP2, the F-box substrate-recognition protein of an E3 ubiquitin ligase that normally tags the cell cycle brake P21 for destruction. Deprived of AKT’s stabilizing phosphorylation, SKP2 itself was degraded through the proteasome, P21 accumulated in the nucleus, and the cells arrested in G0/G1 and died. Clinical databases reinforced the story: both GRP94 and SKP2 are overexpressed in hepatocellular carcinoma tissues and correlate with poor survival.

The death program did not stop at apoptosis. With AKT signaling crippled, the antioxidant defenses of the cell, maintained through the AKT-mTOR axis, Nrf2 and GSK-3beta, eroded, and reactive oxygen species accumulated. Mitochondrial membrane potential collapsed, lipid peroxidation measured as malondialdehyde rose, the ferroptosis gatekeeper GPX4 fell, and labile iron climbed, all hallmarks of ferroptosis, the iron-dependent form of regulated cell death. The ROS scavenger N-acetylcysteine and the ferroptosis inhibitor liproxstatin-1 each blunted these effects, confirming causality. KGA-1002 thus kills liver cancer cells along two converging routes, ER stress-driven apoptosis and AKT-dependent ferroptosis, both traceable to a single upstream lesion at GRP94.

In vivo, the compound held up. In nude mice bearing subcutaneous SK-Hep-1 tumors, intraperitoneal KGA-1002 at 15, 30 and 60 milligrams per kilogram over 60 days shrank tumors by 44.1, 52.1 and 53.5 percent, with the top dose matching sorafenib; direct intratumoral injection performed even better, reaching 61.6 percent inhibition. Tumors from treated animals showed reduced Ki67 staining and elevated phosphorylated IRE1 and PERK, confirming that the ER stress mechanism operates in living tissue. The decisive target-validation experiment came from xenografts grown from GRP94-knockdown cells: with the target partially removed, the drug’s antitumor effect and its suppression of Ki67 were significantly weakened, establishing that KGA-1002’s efficacy is GRP94-dependent. Safety readings were reassuring, with no weight loss, behavioral changes, liver or kidney function abnormalities, and no histopathological organ damage even at 150 milligrams per kilogram in a separate subacute study.

The study’s authors are careful about scope, and so should readers be. The work rests on cell lines and subcutaneous mouse models, not orthotopic liver tumors or patients, and a selectivity index of roughly 1.5 to 1.7 over normal hepatocytes, while adequate, leaves room for optimization. Yet the conceptual payoff is substantial: GRP94 has been implicated in breast cancer metastasis and multiple myeloma, and the authors note it is also overexpressed in colon, esophageal and bladder cancers, so a validated, covalent, isoform-selective inhibitor scaffold is a tool the wider oncology community can build on. By showing exactly where the molecule docks, which residue it attacks, and how that single molecular event cascades through protein folding, calcium handling, AKT stability, SKP2 degradation and ferroptosis, the Kunming team has delivered something rarer than another cytotoxic natural product: a mechanistically coherent proof that GRP94 is a druggable vulnerability in liver cancer, and a lead compound engineered to exploit it.

Subject of Research: A selective GRP94 inhibitor derived from a guaianolide sesquiterpenoid dimer as a therapeutic agent against hepatocellular carcinoma

Article Title: Guaianolide dimer KGA-1002 targets GRP94 and triggers unfolded protein response-associated degradation of SKP2/AKT axis as a novel antihepatoma agent

Article References: Li, Q.-H., Li, T.-Z., Wang, Y.-C., Huang, X.-Y., Ma, W.-J., Li, F.-J., Huang, F.-D., Hu, M.-M., & Chen, J.-J. (2026). Guaianolide dimer KGA-1002 targets GRP94 and triggers unfolded protein response-associated degradation of SKP2/AKT axis as a novel antihepatoma agent. Journal of Advanced Research, 88, 1077-1093. https://doi.org/10.1016/j.jare.2026.01.010

Image Credits: AI Generated

DOI: 10.1016/j.jare.2026.01.010

Keywords: hepatocellular carcinoma, GRP94, KGA-1002, guaianolide dimer, unfolded protein response, AKT, SKP2, P21, ferroptosis, endoplasmic reticulum stress, natural products, drug discovery

The cells in question are senescent vascular smooth muscle cells, and recent single-cell lineage-tracing studies have pushed a striking reframing of atherosclerosis as a tumor-like disease driven by these very cells. Within plaques, vascular smooth muscle cells undergo clonal expansion, dedifferentiation, and metabolic reprogramming, forming pathological structures that resemble solid tumors. The senescent subset behaves like drug-resistant dormant tumor cells: they persist indefinitely, resist apoptosis, and remodel their surroundings through the senescence-associated secretory phenotype, a cocktail of inflammatory signals that drives necrotic core expansion and thins the fibrous cap that keeps plaques from rupturing. Selectively killing these cells, an approach known as senolysis, has already shown promise for extending lifespan in animal studies, but translating that promise into cardiovascular medicine has been hampered by toxicity concerns with existing drug candidates.

The new study began with a deceptively simple observation. When the researchers modeled senescence in human aortic smooth muscle cells by exposing them to palmitate, a lipid that mimics the lipotoxic stress of atherosclerosis, the cells entered a stable senescent state marked by elevated beta-galactosidase activity and upregulation of the cell-cycle inhibitors p16 and p21. Crucially, the cells also ramped up production of heat shock protein 90 alpha, or HSP90α, a chaperone molecule famous in oncology as a scaffold that supports the survival of tumor cells. Given the parallels between tumorigenesis and atherogenesis, the team hypothesized that senescent smooth muscle cells might exploit the same HSP90α machinery to maintain homeostasis and evade death in the hostile plaque microenvironment.

Proteomic analysis after HSP90α knockdown revealed what that machinery was protecting. Silencing HSP90α specifically activated the PERK/eIF2α/ATF4/CHOP arm of the endoplasmic reticulum stress response, suggesting that high HSP90α levels actively restrain this stress pathway in senescent cells. The team then turned to human tissue, integrating four published single-cell RNA sequencing datasets covering 40 samples of human atherosclerotic lesions from carotid endarterectomy and coronary arteries. In senescent smooth muscle cells identified by co-expression of p21 and p16, HSP90α was highly expressed, but the CHOP stress marker was conspicuously absent. Immunofluorescence of human carotid plaques confirmed the same spatial dissociation, and cultured senescent cells showed suppression of the PERK branch specifically, while the ATF6 and IRE1 branches of the unfolded protein response remained untouched.

The mechanism behind that selective suppression proved to be an elegant piece of molecular scaffolding. Prior work had shown that the kinase AKT can bind to the autophosphorylation site of PERK and block its activation. Using protein-protein docking, co-immunoprecipitation, and domain mapping, the researchers demonstrated that HSP90α holds AKT and PERK together in a ternary complex, with the middle region of HSP90α, amino acids 284 through 620, sufficient to bind both partners. In senescent cells this interaction intensifies, stabilizing AKT and keeping PERK dormant. When HSP90α was removed, AKT degraded rapidly through the proteasome, PERK signaling surged, and the senescent cells began to die. Reactivating the pathway with thapsigargin, a specific inducer of endoplasmic reticulum stress, collapsed mitochondrial membrane potential and pushed the cells into apoptosis while reducing their senescence markers.

The downstream killing mechanism runs through calcium. PERK activation is known to tighten physical contacts between the endoplasmic reticulum and mitochondria, and the team documented exactly that: after HSP90α knockdown or thapsigargin treatment, transmission electron microscopy showed expanded mitochondria-associated ER membranes, fluorescent probes confirmed elevated mitochondrial calcium, and the calcium flux funneled through the mitochondrial calcium uniporter, MCU. Blocking mitochondrial calcium uptake with ruthenium red, or silencing MCU directly, rescued the cells from apoptosis. In other words, the senescent cells survive only as long as PERK stays suppressed; once the brake is released, calcium floods the mitochondria, membrane potential collapses, and the cell self-destructs.

Having defined the target, the team went hunting for a drug. They compiled a dataset of 112 natural products with documented anti-atherosclerotic activity from a literature search spanning 1947 to 2024, then docked each compound against the crystal structure of HSP90α using three independent docking programs and a robust rank aggregation method. The top hit was salvianolic acid A, or SAA, a water-soluble polyphenol from Salvia miltiorrhiza, the red sage root used in traditional Chinese medicine. Its docking score rivaled that of 17-DMAG, a well-characterized synthetic HSP90 inhibitor. Two independent binding assays sealed the case: a cellular thermal shift assay showed that SAA stabilizes HSP90α against heat denaturation, and a biotinylated SAA probe pulled down endogenous HSP90α from cell lysates, confirming direct physical binding.

SAA’s effects on senescent cells were strikingly selective. At concentrations of 20 to 100 micromolar, it triggered apoptosis in senescent smooth muscle cells, reduced p16 and p21, and suppressed secretion of the inflammatory SASP factors IL-1α and IL-6, while leaving normal smooth muscle cells unharmed. Mechanistically, SAA disrupted the HSP90α-AKT-PERK ternary complex, shifted AKT ubiquitination from the K63-linked form toward K48-linked chains that mark proteins for proteasomal destruction, and thereby reactivated PERK signaling. Overexpressing HSP90α reversed all of these effects, and knocking down PERK rescued the cells, confirming that the pathway runs through the complex the team had identified. A cross-linking assay even captured the intact 340-kilodalton ternary complex and watched it dissolve after SAA treatment.

The in vivo results were equally compelling. In ApoE-deficient mice fed a high-fat diet for 20 weeks, intraperitoneal SAA from week 9 onward significantly reduced plaque area, shrank necrotic cores, thickened fibrous caps, and cut lipid accumulation in the aorta, while lowering serum IL-6. Using adeno-associated viruses to manipulate HSP90α specifically in vascular smooth muscle cells, the researchers showed that VSMC-specific knockdown increased p21-CHOP colocalization in plaques, whereas overexpression blunted SAA’s effects and caused a rebound of p21-positive cells. Co-immunoprecipitation from mouse aortas confirmed that SAA weakened the HSP90α-AKT-PERK interaction in living tissue, closing the loop between the cell culture mechanism and the animal outcome.

What makes this work resonate beyond the lab bench is SAA’s clinical head start. Unlike geldanamycin-derived HSP90 inhibitors, whose toxicity has blocked every approval attempt in oncology, SAA is already in a phase II trial for diabetic microangiopathy and two phase I trials for angina pectoris and diabetes, suggesting a tolerability profile that could accelerate translation. The authors caution that mouse-to-human translation is complex and that whether SAA can actually reverse plaque progression will require endpoint clinical trials. Still, the study delivers something the senolytics field has lacked: a senolytic strategy grounded in a defined survival mechanism of the target cells, delivered by a natural compound with human safety data, and validated from molecular docking all the way to plaque stabilization. If the findings hold, the humble red sage root may offer a way to evict the zombie cells that make aging arteries fragile.

Subject of Research: Targeting the HSP90α-AKT-PERK complex in senescent vascular smooth muscle cells as a senolytic strategy against atherosclerosis

Article Title: Salvianolic Acid a Disrupts the HSP90α‐AKT‐PERK Ternary Complex to Alleviate Atherosclerosis by Activating Endoplasmic Reticulum Stress of Senescent Vascular Smooth Muscle Cells

Article References: Guan, X., Lu, M., Cui, X., Zhang, D., Zhang, L., Lin, L., Li, Y., Hu, Y., & Li, C. (2026). Salvianolic Acid a Disrupts the HSP90α‐AKT‐PERK Ternary Complex to Alleviate Atherosclerosis by Activating Endoplasmic Reticulum Stress of Senescent Vascular Smooth Muscle Cells. Advanced Science, Article e77891. https://doi.org/10.1002/advs.77891

Image Credits: AI Generated

DOI: 10.1002/advs.77891

Keywords: atherosclerosis, senescence, senolytics, HSP90α, PERK, endoplasmic reticulum stress, vascular smooth muscle cells, salvianolic acid A, SASP, mitochondrial calcium, AKT, plaque stability

The drug targets the phosphatidylinositol-4,5-bisphosphate 3-kinase, AKT, mechanistic target of rapamycin signaling cascade, a central growth and survival pathway that is frequently dysregulated in both canine and human cancers. When this pathway runs amok, it drives neoplastic cells to proliferate relentlessly, evade apoptosis, crank up metabolism, and, in the case of lymphoid malignancies, stimulate the production of vascular endothelial growth factor, a molecule that supports tumor neovascularization. Because single-node inhibitors of the pathway often deliver only brief or incomplete responses, likely due to well-known feedback loops within the signaling network, the researchers turned to VDC597, a compound that blocks PI3K along with both mTOR complexes, mTORC1 and mTORC2, thereby hitting the pathway at multiple points simultaneously.

In their experiments, the team tested VDC597 against two canine cell lines: 1771, derived from a spontaneously occurring B-cell lymphoma, and CLL1390, derived from chronic lymphocytic leukemia. Both lines had previously been documented to carry mutations in or constitutively express activated proteins of the PI3K-AKT-mTOR pathway, making them appropriate models for pathway-targeted therapy. Western blot analysis showed that a 24-hour treatment with the drug produced a clear, dose-dependent reduction in phosphorylated AKT at the serine 473 residue, the molecular signature of pathway activation. The leukemia line proved more sensitive, showing significant suppression at concentrations as low as 0.2 micromolar, while the lymphoma line required a full micromolar dose to achieve statistically significant inhibition.

Timing experiments revealed that the drug’s effects on signal transduction are both rapid and durable. Following a single 1 micromolar dose, phosphorylation of AKT dropped quickly and remained at roughly half of control levels for a full 24 hours. Downstream phosphorylation of 4EBP1, a translation-regulating target of mTORC1, fell even more sharply, with statistically significant suppression measurable from half an hour after treatment through the two-hour mark. The researchers verified these biochemical findings by immunohistochemistry on fixed cell pellets, observing reduced perinuclear and cytoplasmic staining for both phosphoproteins after drug exposure, an encouraging confirmation that the compound shuts down signaling across the entire pathway rather than just a single branch.

The functional consequences were equally striking. After 72 hours of exposure, VDC597 halved the viable cell population at concentrations within or near what is pharmacologically achievable, with mean half-maximal inhibitory concentrations of 1.41 micromolar for CLL1390 and 2.56 micromolar for 1771, values informed by an earlier phase I trial of the drug in tumor-bearing dogs. Live-cell imaging, tracking fluorescently labeled nuclei and dead-cell stains over 48 hours, showed that the drug did not merely slow proliferation: it actively killed the lymphoma cells, with cell death increasing in a dose-dependent manner and becoming significantly elevated at concentrations of 0.25 micromolar and above. Enzyme-linked immunosorbent assays further demonstrated that VDC597 suppressed vascular endothelial growth factor production in both cell lines, again in a dose-dependent fashion, suggesting the drug may undermine the angiogenic support system that lymphoid tumors rely upon.

Because combination therapy, not single agents, ultimately determines how well targeted drugs translate into clinical benefit, the team paired VDC597 with the three chemotherapy drugs most commonly used in canine lymphoma protocols: dexamethasone, doxorubicin, and vincristine. The results were revealing. Combining VDC597 with dexamethasone produced genuinely synergistic growth inhibition, quantified by combination indices below 1 using the Chou-Talalay method, with the effect strongest at lower drug concentrations. Pairing the drug with doxorubicin yielded additive to mildly synergistic effects at lower doses, though the highest doxorubicin concentration produced antagonism, possibly because PI3K inhibition dampens the reactive oxygen species generation through which doxorubicin promotes apoptosis. Vincristine, whose mechanism overlaps with the pathway’s role in microtubule function during mitosis, showed only additive to mildly antagonistic interactions.

The strong synergy with dexamethasone is mechanistically compelling. Glucocorticoids kill lymphoid cells through receptors whose nuclear translocation and downstream signaling are potentiated by PI3K-AKT-mTOR inhibition, a finding previously documented in human B-cell acute lymphoblastic leukemia. The Colorado State results thus support the hypothesis that adding a dual PI3K/mTOR inhibitor to standard chemotherapy could deepen responses or sensitize resistant tumors, particularly in lymphoma, where the clinical reservoir of effective options is thin.

Importantly, the study went beyond cell culture to examine pathway activation in actual patients. Using tissue microarrays built from 118 lymph node samples collected from 84 dogs with spontaneous B-cell lymphoma, the researchers scored phosphorylated AKT and phosphorylated 4EBP1 by immunohistochemistry, employing both traditional manual Allred scoring and artificial intelligence-assisted whole-slide analysis with Visiopharm software to generate finer-grained H-scores. The two approaches correlated well, validating the use of machine learning tools for quantitative pathology in veterinary specimens. The phosphorylation signals proved highly variable from tumor to tumor, underscoring that not every canine B-cell lymphoma is driven by an equally active PI3K-AKT-mTOR pathway.

Two clinically meaningful correlations emerged. First, tumors with lower expression of major histocompatibility complex class II, a known adverse prognostic marker measured by flow cytometry, showed significantly higher levels of phosphorylated AKT, linking aggressive immune phenotype to stronger pathway activity. Second, samples taken after relapse following CHOP chemotherapy showed higher phosphorylated 4EBP1 than matched pre-treatment samples, a result that retained significance in paired manual scoring. However, no correlation was found between either phosphoprotein and progression-free interval, overall survival, WHO stage or substage, or flow cytometric immunophenotypic markers, and phosphorylated AKT did not rise in parallel with phosphorylated 4EBP1 in the relapse samples. The authors caution against overinterpreting these limited associations and suggest several possible explanations, including AKT phosphorylation at sites not detected by the assay, alternative 4EBP1 kinases such as PIM2 or RAS/MAPK signaling, or mutations downstream of AKT.

The study has clear limitations that its authors acknowledge. Only one cell line each was tested for lymphoma and leukemia, so the full heterogeneity of canine lymphoid malignancies, including T-cell lymphoma and acute lymphoblastic leukemia, remains unexplored. No washout experiments were performed to determine how long signaling stays suppressed after the drug is withdrawn, information that would be essential for designing oral dosing schedules. And the finding of elevated phosphorylated 4EBP1 without corresponding phosphorylated AKT in relapsed tumors awaits mechanistic confirmation. Nevertheless, the core message is clear: VDC597 collapses PI3K-AKT-mTOR signaling, kills lymphoid cancer cells in vitro at achievable concentrations, synergizes with dexamethasone, and may sensitize tumors to standard chemotherapy. As dogs with spontaneous diffuse large B-cell lymphoma are increasingly recognized as valuable models for human non-Hodgkin lymphoma, these results position dual PI3K/mTOR inhibition as a strategy worth advancing toward larger cell line panels, animal studies, and ultimately clinical trials in both species.

Subject of Research: Evaluation of the dual PI3K/mTOR inhibitor VDC597 against canine B-cell lymphoma and chronic lymphocytic leukemia cells in vitro, with immunohistochemical assessment of PI3K-AKT-mTOR pathway activation in spontaneous canine B-cell lymphoma.

Article Title: In vitro effects of the PI3K/mTOR dual-inhibitor, VDC597, in canine lymphoma and leukemia

Article References: Meuten, T., Brill, S. A., Brady, R. V., Farrell, K. B., Rose, B. J., Schlein, L. J., & Thamm, D. H. (2026). In vitro effects of the PI3K/mTOR dual-inhibitor, VDC597, in canine lymphoma and leukemia. Veterinary Oncology, 3(1), Article 13. https://doi.org/10.1186/s44356-026-00065-4

Image Credits: AI Generated

DOI: 10.1186/s44356-026-00065-4

Keywords: canine lymphoma, canine leukemia, VDC597, PI3K, mTOR, AKT, 4EBP1, signal transduction, chemotherapy, immunohistochemistry, veterinary oncology, drug combination