The researchers, led by Mami Amaki and Yasutomo Imai, hypothesized that caspase-1 might control IL-33 release from keratinocytes in vivo. Their reasoning drew on a parallel case: IL-1α, like IL-33, is a nuclear cytokine stored under steady-state conditions, and its extracellular release requires caspase-1. Previous studies, however, had suggested that IL-33 release is independent of caspase-1, but those conclusions came largely from non-cutaneous tissues or in vitro systems. In the airway epithelium, for example, allergen protease-activated stress granule assembly and gasdermin D fragmentation have been shown to control IL-33 secretion without caspase-1. The Japanese team suspected that the skin might operate by different rules, and their new findings support that idea.

The first technical step was to establish where caspase-1 actually resides in skin. Using immunofluorescence staining of mouse skin sections with a Cy3-conjugated anti-caspase-1 P10 polyclonal antibody, the researchers detected caspase-1 immunoreactivity in the nuclei of epidermal keratinocytes. No specific staining appeared in caspase-1/11-deficient mice, which served as negative controls. This was a significant observation because earlier studies had concluded that caspase-1 expression was restricted to hematopoietic cells, conclusions based largely on the absence of detectable interleukin-1 beta-processing activity and the limited sensitivity of the detection methods available at the time. Subsequent work with improved methodologies has revealed low-level but functional caspase-1 expression in epithelial cells, including keratinocytes. For caspase-1 to be involved in the release of a nuclear alarmin like IL-33, the protease would need to be present in keratinocyte nuclei, and the new staining data confirm exactly that.

Next, the team examined what happens to nuclear IL-33 when the skin is stimulated. They applied 20 microliters of 0.5 percent 2,4-dinitrofluorobenzene (DNFB), a contact-sensitizing hapten dissolved in acetone and olive oil, to the left ear of mice while the right ear received vehicle alone. Six hours later, they processed the ear skin for immunofluorescence staining for IL-33, using an affinity-purified rabbit anti-mouse IL-33 polyclonal antibody detected with a biotinylated goat anti-rabbit IgG secondary antibody and streptavidin-conjugated Alexa Fluor 594, with nuclei counterstained using DAPI. The disappearance of nuclear IL-33 staining in keratinocytes was interpreted as evidence that IL-33 had been released into the extracellular space, an established surrogate readout that parallels findings in experimental allergic rhinitis, where allergen challenge induces a rapid loss of IL-33 staining in nasal epithelial cells alongside increased IL-33 levels in nasal lavage fluids.

The result was striking. In wild-type mice, IL-33 fluorescence in the epidermis was substantially reduced six hours after DNFB treatment, consistent with the team’s previous report that cutaneous stimulation triggers extracellular IL-33 release in vivo. In caspase-1/11-deficient mice, however, IL-33 immunoreactivity remained clearly detectable in the nuclei of epidermal keratinocytes at the same time point. In other words, deleting caspase-1/11 prevented the DNFB-induced loss of keratinocyte IL-33. Notably, quantitative real-time PCR showed that DNFB application increased Il33 mRNA expression in both wild-type and caspase-1/11-deficient mice, even though nuclear IL-33 staining persisted in the knockout animals. This indicates that Il33 transcription is induced by DNFB independently of IL-33 release, meaning the protease is specifically required for the release step rather than for the transcriptional response.

To test whether this release mechanism matters for actual disease, the researchers crossed their caspase-1/11-deficient mice with the hK14mIL33tg transgenic line, which overexpresses murine IL-33 in keratinocytes under the control of the human keratin-14 promoter. These IL33tg mice spontaneously develop atopic dermatitis-like skin inflammation. When caspase-1/11 was deleted in this background, the resulting IL33tg Casp1/11KO mice exhibited markedly attenuated skin inflammation compared with IL33tg mice. Histological examination of hematoxylin and eosin-stained skin sections showed pronounced leukocyte and eosinophil infiltration accompanied by epidermal hyperplasia in IL33tg mice, while these pathological features were minimal in the double-deficient animals, indicating a substantially reduced inflammatory response in the absence of caspase-1/11.

The molecular signature of the type 2 immune response told the same story. Quantitative PCR analysis of skin tissue, performed with a TaqMan RNA-to-Ct Kit and an ABI7900HT sequence detection system, revealed significant reductions in the expression of type 2 cytokines including Il4, Il5, and Il13, as well as Prg2, which encodes eosinophil peroxidase and serves as a specific marker of murine eosinophils. The reduction in Prg2 expression was consistent with the histological findings showing markedly reduced eosinophil infiltration in IL33tg Casp1/11KO mice. Together, these data indicate that caspase-1/11 deficiency suppresses IL-33-driven type 2 immune responses in the skin, dampening the entire downstream allergic cascade that IL-33 normally sets in motion through ILC2 activation.

The findings carry important caveats that the authors address candidly. The knockout mice used in the study have historically been described as caspase-1-deficient, but they are now recognized to carry a combined deficiency of both caspase-1 and caspase-11, because the Casp1 and Casp11 genes lie in close genomic proximity within the same gene cluster, resulting in simultaneous disruption of both loci in this strain. The potential contribution of caspase-11 therefore cannot be formally excluded. However, previous studies indicate that epithelial inflammasome-related responses, including IL-33 regulation, are mainly mediated by caspase-1 rather than caspase-11. Caspase-11 is primarily implicated in noncanonical inflammasome signaling in myeloid cells and localizes predominantly in the cytoplasm, making its direct involvement in the nuclear export of IL-33 from keratinocytes less likely. The authors also note that loss of nuclear staining does not directly quantify extracellular IL-33 levels, so future studies using biochemical measurements will be needed to confirm the release mechanism.

There is another puzzle worth noting. Several studies have suggested a role for caspase-1 in IL-33 inactivation rather than release, since IL-33 can be inactivated after maturation by caspase-1. If caspase-1-mediated inactivation were essential in vivo, IL-33-transgenic mice lacking caspase-1/11 would be expected to show exacerbated skin inflammation, yet the opposite was observed. The authors also point out that pharmacological inhibition of caspase-1 may not fully reflect its role in alarmin release, because for IL-1α the presence of caspase-1 protein, rather than its enzymatic activity, can be required for secretion. Because caspase-1/11 was deleted in all cells in the mice used, the possibility that caspase-1 deficiency in immune cells influences IL-33-induced skin inflammation cannot be excluded, though the marked reduction in inflammation suggests that caspase-1/11 deficiency affects an early step in IL-33-driven skin inflammation, most likely IL-33 release from keratinocytes.

The broader implication is that alarmin biology may be tissue-specific in ways the field has not fully appreciated. IL-33 can be released independently of caspase-1 in other tissues, notably the airway epithelium, where gasdermin D-mediated pathways dominate. But in the skin, the new evidence suggests that caspase-1 is involved in the pathogenic release of IL-33 from keratinocytes in vivo, and that this release step is a critical control point for atopic dermatitis-like inflammation. If the findings hold up in biochemical assays and in human tissue, they could reshape how researchers think about targeting IL-33 in atopic dermatitis, pointing to the release machinery within keratinocytes as a potential therapeutic frontier alongside the IL-33-blocking antibodies already in clinical development.

Subject of Research: Immunology

Article Title: Deficiency of inflammatory caspases attenuates IL-33–mediated dermatitis

Article References: Amaki, M., Murata, T., Kanazawa, N., & Imai, Y. (2026). Deficiency of inflammatory caspases attenuates IL-33–mediated dermatitis. Journal of Cutaneous Immunology and Allergy, 9, Article 16358. https://doi.org/10.3389/jcia.2026.16358

Image Credits: AI Generated

DOI: 10.3389/jcia.2026.16358

Keywords: atopic dermatitis, IL-33, caspase-1, keratinocytes, alarmin, skin inflammation, type 2 cytokines, innate lymphoid cells, Deficiency, inflammatory, caspases, attenuates

The breakthrough came from a technical challenge. Unlike in the nematode C. elegans, where cell corpses can be spotted with Nomarski microscopy, dying cells are invisible in live Drosophila tissues. Steller’s laboratory first developed a technique using the vital dye acridine orange to visualize apoptotic cells in live fly embryos. Screening a collection of 129 chromosomal deletions covering more than half of the genome, only three overlapping deletions on the third chromosome produced embryos completely lacking acridine orange staining. A smaller deletion, Df(3R)H99, narrowed the interval, and chromosomal walking across the entire H99 region allowed the team to isolate the genes responsible for the cell-death phenotype.

Reaper was the first gene identified in that interval. Strikingly, its mRNA distribution largely anticipated the pattern of apoptosis in the Drosophila embryo, suggesting that the gene acts as a global convergence point for many different signaling pathways. Subsequent studies confirmed that reaper is a direct transcriptional target of an extraordinary range of inputs: Hox genes, segmentation genes, steroid hormone signaling, p53, microRNAs, JNK signaling, and histone-modifying enzymes. In contrast to its vast regulatory region, reaper encodes a tiny 65-amino-acid protein bearing an N-terminal IAP-binding motif (IBM) that mediates direct binding to and neutralization of DIAP1, the major inhibitor of apoptosis in flies.

That mechanism introduced a principle that now underpins cell death regulation across higher animals: apoptosis can be triggered by precisely controlled expression of IAP antagonists, rather than activation of caspases alone. DIAP1 is an essential survival factor required to prevent unwanted caspase activation in virtually all somatic cells. In living cells, DIAP1 and its mammalian counterpart XIAP repress caspases by direct binding and ubiquitylation. Deleting the RING domain of either protein completely abrogates anti-apoptotic activity, demonstrating that the E3-ligase function of these IAPs is essential and evolutionarily conserved. Once Reaper accumulates in a doomed cell, it binds DIAP1 and promotes self-conjugation and degradation of the protein, removing the major brake on caspase activity in a rapid switch of cell fate.

Reaper did not act alone. Shortly after its isolation, two additional pro-apoptotic genes, head involution defective (hid) and grim, were identified in the same H99 region, and a fourth family member, sickle, was found in 2002. Collectively known as RHG genes, they share an N-terminal IBM, a role in developmental apoptosis, and regulation by multiple developmental and stress pathways. Hid, a 410-amino-acid protein, is a direct molecular target of the Ras-MAPK pathway: survival signals activate MAPK, which phosphorylates and inhibits Hid, thereby saving cells that are primed to die. This mechanism is used, for example, to match the number of glial cells in the Drosophila CNS midline to neurons, which secrete the TGFα-like ligand Spitz that activates EGFR only on glial cells in contact with neurons.

The RHG proteins also cooperate through hetero-multimerization. Reaper and Grim contain an α-helical GH3 domain that promotes multimerization and localization to the outer mitochondrial membrane. Co-expression of grim with reaper or hid induces significantly higher levels of cell death than expression of these genes individually. Hid localizes to mitochondria via its C-terminal transmembrane domain and can recruit Reaper to the mitochondrial outer membrane, allowing more effective killing. Some cell types, including embryonic neuroblasts, do not express Hid and are killed by coordinated expression of reaper, grim, and possibly sickle, underscoring that different cell types have differential requirements for these proteins.

The conceptual bridge to mammals came six years after reaper, with the identification of Smac/DIABLO, Omi/HtrA2, and ARTS as mitochondrial IAP antagonists. The IBM is structurally conserved between Drosophila and mammalian IAP-antagonists and is required for IAP-binding and cell killing. Smac/DIABLO and Omi/HtrA2 reside in the mitochondrial intermembrane space and require mitochondrial outer membrane permeabilization to access cytosolic IAPs. ARTS, by contrast, shares no obvious sequence homology with RHG proteins but many functional similarities with Reaper: it does not require MOMP, acts upstream of cytochrome c and Smac/DIABLO, induces ubiquitin-proteasome-mediated degradation of XIAP, and is transcriptionally induced upon DNA damage by direct binding of p53 to its promoter. Inactivation of ARTS in mice elevates XIAP protein levels and attenuates stem cell apoptosis, suggesting ARTS may be a functional analog of Reaper.

Beyond the core machinery, Drosophila has proven indispensable for understanding caspase regulation in vivo. The initiator caspase Dronc is homologous to mammalian caspase-9 and requires binding to Dark, the Apaf-1 homolog, to form the apoptosome. Drice and Dcp-1 are caspase-3-like effector caspases that carry out cellular demolition. Although cytochrome c appears not strictly required for apoptosome activation in flies, mutations can delay developmental apoptosis, consistent with the idea that cytochrome c accelerates rather than initiates the caspase cascade. Mitochondrial dynamics and reactive oxygen species also critically influence cell death outcomes, and the Drosophila apoptosome functions analogously to its mammalian counterpart, making the fly a powerful model for caspase biology.

One of the most striking lessons from the fly is that apoptosis is not merely a demolition crew. Over the last two decades, Drosophila has emerged as a leading model for non-lethal roles of caspases in development, tissue remodeling, cell differentiation, proliferation, and neuronal remodeling. The first mechanistic proof that apoptotic caspases can drive differentiation without inducing apoptosis came from mouse lens fiber cell differentiation, overturning the dogma that caspases are inherently lethal. In Drosophila, caspase activity is essential for spermatid individualization, where inhibition prevents cytoplasmic clearance and results in male sterility. During metamorphosis, larval neurons prune their axons and dendrites in response to the steroid hormone ecdysone, and this remodeling requires localized activation of Dronc selectively within neurites destined for removal. Robust maintenance of DIAP1 and survival pathways in the soma ensures apoptotic thresholds are never reached, allowing a micro-apoptotic program powerful enough to remodel defined domains while preserving viability.

Drosophila also revealed that apoptotic cells can release mitogenic signals to stimulate proliferation of neighboring cells, a phenomenon now generally referred to as apoptosis-induced proliferation (AiP). Cells undergoing apoptosis in response to DNA damage stimulate proliferation of neighboring cells and aid tissue regeneration, mediated by p53-driven transcriptional activation of reaper and hid, inhibition of DIAP1, and de-repression of caspases. JNK signaling stimulates a positive feedback loop between p53 and RHG genes that amplifies the initial stimulus. The mitogens secreted by apoptotic cells include Wingless, Decapentaplegic, and Hedgehog. Because AiP is evolutionarily conserved, these findings carry obvious implications for tissue regeneration and cancer: chemotherapy using DNA-damaging agents may cause AiP, which in turn may contribute to the formation of metastases.

In 1994, PCD was basically synonymous with apoptosis. Since then, many forms of non-apoptotic PCD have been described, including autophagy-dependent developmental cell death, regulated necrosis, pyroptosis-like inflammatory death, and immune-induced death. While a direct physiological role of reaper in these processes remains to be demonstrated, reaper may contribute under pathological conditions. When apoptosis is blocked by caspase inhibitors, Eiger, the fly TNF homolog, can induce necroptosis in a process requiring the initiator caspase Dronc. Since Dronc is inhibited by DIAP1 and this repression is relieved by RHG proteins, reaper and its partners may affect other forms of cell death when core apoptotic pathways are genetically or pharmacologically inhibited.

Due to its genetic and anatomical accessibility, Drosophila continues to drive conceptual advances with relevance to cancer, neurodegeneration, immunity, and regeneration. Over the past three decades, the fly has provided fundamental insights into apoptosis, the non-lethal use of apoptotic proteins, alternative death pathways, and proliferation-death coupling. Many processes controlled by RHG proteins in Drosophila mirror phenomena in vertebrates, and RHG genes will remain essential tools for probing how a constitutively expressed cell suicide program is contained by the layered checkpoints that evolution has built from worms to flies to mammals.

Subject of Research: The legacy of the Drosophila reaper gene in apoptosis research

Article Title: Thirty years of reaper: lessons learned from programmed cell death in Drosophila

Article References: Steller, H. (2026). Thirty years of reaper: lessons learned from programmed cell death in Drosophila. Frontiers in Cell Death, 5, Article 1770008. https://doi.org/10.3389/fceld.2026.1770008

Image Credits: AI Generated

DOI: 10.3389/fceld.2026.1770008

Keywords: apoptosis, reaper, Drosophila, caspases, IAP, programmed cell death, Thirty, years, lessons, learned, programmed, cell

5-fluorouracil, often abbreviated 5-Fu, has been a cornerstone of colorectal cancer treatment for decades. It works by interfering with DNA synthesis, forcing rapidly dividing cells to self-destruct. Yet its clinical performance remains constrained by two persistent problems: limited efficacy in many patients and a spectrum of serious side effects that can force dose reductions or treatment interruptions. These limitations have driven an intensive search for compounds that could sensitize tumors to 5-Fu, allowing lower doses to achieve the same or better effect. The new study positions a bacterial fermentation product as a candidate for exactly that role.

The research team, led by scientists at the Research Institute for Gastroenterology and Liver Diseases at Shahid Beheshti University of Medical Sciences in Tehran, took a systematic approach to comparing three different preparations of L. reuteri, a strain catalogued as IBRC-M 10755. They tested live bacteria, heat-killed bacteria, and the cell-free supernatant, the liquid fraction left behind after the bacteria are removed, which contains the bacterium’s secreted metabolites, proteins, and other molecules. Each preparation was applied to SW-480 cells, a well-established laboratory model of colorectal cancer, both alone and in combination with 5-fluorouracil across concentrations ranging from 1 to 100 micromolar, over 24 to 48 hours.

The results revealed a striking hierarchy among the three preparations. Live L. reuteri, tested at multiplicities of infection of 1, 10, and 100, had no effect on cancer cell viability at any concentration. Heat-killed bacteria at the highest multiplicity of infection, 100, reduced viability by up to 85 percent. The cell-free supernatant, tested at total protein concentrations of 1, 10, 25, and 50 micrograms per milliliter, cut viability by up to 78 percent at 25 micrograms per milliliter and 65 percent at 50 micrograms per milliliter, with statistical significance relative to untreated cells. The pattern suggests that whatever anticancer activity the bacterium possesses resides largely in what it secretes rather than in the living organism itself.

To understand how the supernatant killed the cancer cells, the researchers turned to the molecular machinery of apoptosis. Using quantitative real-time PCR, they measured the expression of five genes that act as regulators and executors of programmed cell death: Bax, a pro-apoptotic member of the Bcl-2 family; Bcl-2, its anti-apoptotic counterpart; and the initiator and executioner caspases 8, 9, and 3. Treatment with live bacteria, heat-killed bacteria at the highest dose, and the supernatant at 25 to 50 micrograms per milliliter all significantly increased the expression of Bax, caspase-3, caspase-8, and caspase-9. The simultaneous engagement of both the extrinsic pathway, signaled through caspase-8, and the intrinsic pathway, signaled through caspase-9, points to a broad activation of the cell’s suicide program rather than a single narrow trigger.

Flow cytometry provided independent confirmation. Cells stained with fluorescent markers that distinguish early apoptotic cells from late apoptotic and necrotic ones showed a dose-dependent increase in apoptosis following supernatant treatment, rising in step with the concentration of total protein applied. This dose-response relationship is an important technical detail, because it indicates a genuine pharmacological effect rather than random toxicity. It also aligns the gene expression data with the functional outcome: cells exposed to higher concentrations of the bacterial supernatant not only talked the apoptotic talk at the RNA level but actually walked the walk, dying at measurably higher rates.

The most clinically intriguing result emerged when the supernatant was combined with 5-fluorouracil. Co-treatment with the cell-free supernatant and a relatively low 10 micromolar dose of the drug produced greater expression of apoptosis-related genes and a higher apoptosis rate than either agent achieved alone. In practical terms, the bacterial metabolites appeared to lower the threshold at which the cancer cells capitulated to the chemotherapy. If this synergy could be reproduced in a living tumor, it might eventually allow oncologists to achieve therapeutic effects with reduced 5-Fu exposure, potentially sparing patients some of the drug’s harsh side effects, which include bone marrow suppression and gastrointestinal toxicity.

The study also examined the inflammatory dimension of the interaction. 5-fluorouracil is known to provoke inflammatory signaling, and chronic inflammation in the tumor microenvironment can undermine treatment. When SW-480 cells received the combined treatment, the drug-induced elevation of messenger RNA for two key inflammatory cytokines, tumor necrosis factor alpha and interleukin-1 beta, was significantly blunted. However, the researchers noted an important caveat: when they measured the actual secreted protein levels of these cytokines by enzyme-linked immunosorbent assay, the reduction was not consistently reflected. This discordance between mRNA and protein levels is a familiar challenge in molecular biology and underscores that transcriptional changes do not always translate cleanly into changes in secreted signaling molecules.

The authors are careful to frame their findings as preliminary. Because the work was conducted entirely in vitro, on a single cell line in culture dishes, it cannot speak to how the supernatant would behave in the far more complex environment of a human tumor, where immune cells, blood supply, and drug metabolism all intervene. The researchers explicitly call for formal combination-index analysis, a mathematical framework for quantifying whether two agents are truly synergistic, additive, or antagonistic, as well as for validation in animal models before any therapeutic claims can be made. The study was funded by the Iran National Science Foundation and the Research Institute for Gastroenterology and Liver Diseases, and the authors declare no competing interests.

Even with those caveats, the study contributes a well-characterized data point to an increasingly active field exploring how probiotic derivatives might complement cancer chemotherapy. The observation that the cell-free supernatant outperformed both live and heat-killed bacteria is particularly noteworthy, because a cell-free preparation would avoid the safety concerns associated with administering live microorganisms to immunocompromised cancer patients. If subsequent work identifies the specific molecules in the L. reuteri supernatant responsible for sensitizing SW-480 cells to 5-fluorouracil, the door could open to standardized, purified adjunct therapies built from the chemistry of the gut microbiome. For now, the message is one of cautious optimism: a familiar probiotic’s secretions, in a petri dish at least, appear to help a fifty-year-old chemotherapy drug finish the job it was designed to do.

Subject of Research: Probiotic-derived cell-free supernatant as an adjunct to 5-fluorouracil chemotherapy in colorectal cancer cells

Article Title: Cell-free supernatant of Limosilactobacillus reuteri enhances 5-fluorouracil-induced apoptosis in SW-480 colorectal cancer cells: an in vitro study

Article References: Saeedi Niasar, M., Sadeghi, A., Tarzemani, S., Safarpour, H., Alipour, S., Ghazvinian, Z., Yazdani, E., & Raeisi, H. (2026). Cell-free supernatant of Limosilactobacillus reuteri enhances 5-fluorouracil-induced apoptosis in SW-480 colorectal cancer cells: an in vitro study. BMC Complementary Medicine and Therapies. https://doi.org/10.1186/s12906-026-05611-z

Image Credits: AI Generated

DOI: 10.1186/s12906-026-05611-z

Keywords: Limosilactobacillus reuteri, 5-fluorouracil, colorectal cancer, apoptosis, cell-free supernatant, probiotics, SW-480 cells, chemotherapy, caspases, Bax, Bcl-2, in vitro study

Bortezomib is not a new molecule. The drug, best known for its role in treating multiple myeloma and mantle cell lymphoma, works by blocking the proteasome, the cellular machinery that degrades damaged or unwanted proteins. When proteasomal degradation grinds to a halt, misfolded proteins accumulate, stress pathways ignite and cells that cannot cope are pushed into programmed death. Earlier clinical and laboratory observations had suggested that bortezomib has activity against CTCL, but the molecular wiring behind that activity had never been fully mapped. The research team, led by Kirti S. Prabhu and Shahab Uddin, set out to answer two linked questions: does bortezomib modulate SKP2-associated cell-cycle regulation in CTCL cells, and can it be combined effectively with the platinum chemotherapy drug cisplatin?

To do this, the investigators used two well-characterized human CTCL cell lines, H9 and HH, exposing them to escalating concentrations of bortezomib and measuring viability with cell counting assays, then probing the consequences with fluorescence imaging and flow cytometry. The drug proved remarkably potent. The 24-hour concentration that killed half the cells, the IC50, was just 5.25 nanomolar in H9 cells and an even lower 1.82 nanomolar in HH cells. Values in the low nanomolar range are notable because they sit comfortably within concentrations achievable in clinical practice, lending translational weight to the laboratory findings. The team then asked what kind of death the cells were dying, and the answer was unambiguous: apoptosis, the orderly suicide program that cancer cells often manage to evade.

The apoptotic signature emerged at several levels simultaneously. Flow cytometry revealed a rising sub-G0/G1 population, a classic hallmark of cells with fragmented DNA, alongside an increase in Annexin V-positive cells, which flag the externalization of phosphatidylserine, an early molecular signal of apoptosis. Immunoblotting showed activation of the caspase cascade, the proteolytic machinery that executes cell death: caspase-8, caspase-9 and caspase-3 were all cleaved into their active forms, and PARP, a DNA repair enzyme that caspase-3 slices as a finishing blow, was cleaved as well. The intrinsic, or mitochondrial, arm of apoptosis was clearly engaged, because the ratio of the pro-death protein Bax to the pro-survival protein Bcl-2 increased, and the mitochondrial membrane potential collapsed, a depolarization event that releases apoptogenic factors from the intermembrane space into the cytosol.

To confirm that this death was truly caspase-dependent, the researchers pre-treated cells with z-VAD-FMK, a broad-spectrum inhibitor that shuts down all caspases. The inhibitor significantly blunted bortezomib-induced apoptosis, demonstrating that the caspase cascade is a functional component of the drug’s cytotoxicity rather than a bystander effect. That finding matters because it anchors bortezomib’s action in a defined, druggable death pathway, one that can be monitored and potentially amplified by rational drug combinations.

Perhaps the most mechanistically revealing part of the study concerns reactive oxygen species, or ROS. Bortezomib treatment increased both cellular and mitochondrial ROS and simultaneously depleted intracellular glutathione, the cell’s principal endogenous antioxidant buffer. This double hit, more oxidants and less antioxidant capacity, creates a state of oxidative stress that damages mitochondrial membranes and feeds the apoptotic circuit. The causal contribution of ROS was tested with N-acetyl-L-cysteine, a glutathione-replenishing antioxidant. When NAC was present, bortezomib’s disruption of the cell cycle, its induction of apoptosis and its activation of caspases were all partially reduced. In other words, oxidative stress is not the whole story, but it is a genuine upstream driver of the cytotoxic program, and the partial rescue suggests that bortezomib kills CTCL cells through converging ROS-dependent and ROS-independent routes.

The study also connected bortezomib’s effects to cell-cycle control, an area where CTCL cells are particularly vulnerable. The team observed a marked suppression of SKP2, S-phase kinase-associated protein 2, an E3 ubiquitin ligase component famous for tagging the cyclin-dependent kinase inhibitors p21 and p27 for destruction. When SKP2 falls, its targets accumulate, and that is exactly what the researchers documented: levels of p21 and p27 rose while the cyclin-dependent kinases CDK4 and CDK6, which drive cells through the G1 checkpoint, declined. This SKP2-p21/p27 axis functions as a brake on proliferation, and bortezomib effectively re-engages that brake. Because SKP2 is an oncogenic driver in many lymphoid malignancies, its suppression offers a candidate pharmacodynamic vulnerability, a measurable molecular endpoint that clinicians could track to confirm that the drug is hitting its intended target in patients.

Combination therapy was the final piece of the puzzle. Platinum-based agents such as cisplatin are mainstays of oncology, but their use in CTCL is limited by toxicity and modest durable benefit. Using the Chou-Talalay method, a widely accepted mathematical framework for quantifying drug interactions through the combination index, the researchers tested whether bortezomib and cisplatin act cooperatively. At selected dose pairings, bortezomib enhanced cisplatin-induced loss of viability and apoptosis, and the interaction was strongly synergistic at 5 nanomolar bortezomib combined with 10 micromolar cisplatin. Synergy means the combination kills more cells than the sum of the two drugs acting alone, a property that could, in principle, allow lower doses of each agent and a narrower toxicity profile. The mechanistic logic is plausible: bortezomib’s ROS generation and caspase priming may lower the apoptotic threshold that cisplatin-induced DNA damage must cross to trigger cell death.

The authors are careful to frame these results as a foundation rather than a clinical verdict. All of the experiments were performed in established cell lines, and the study’s own conclusions call for validation in primary CTCL samples from patients and in in vivo models before the strategy can move toward the clinic. That caveat is standard and appropriate, yet the work still carries real significance. It converts a clinical observation, that bortezomib has activity in CTCL, into a mechanistic account involving ROS accumulation, glutathione depletion, mitochondrial depolarization, caspase activation and SKP2 pathway suppression, and it nominates a specific synergistic drug pairing for further testing. For a disease with limited durable options in its advanced stages, that combination of mechanistic depth and translational direction is exactly the kind of progress that translational medicine aims to deliver, and it gives CTCL researchers a clear set of molecular signposts to follow in the next phase of preclinical and clinical evaluation.

Subject of Research: Proteasome inhibitor bortezomib-induced ROS-dependent mitochondrial apoptosis and SKP2 signaling suppression in cutaneous T-cell lymphoma cells

Article Title: Bortezomib induces ROS-dependent mitochondrial apoptosis and suppresses SKP2 signaling in cutaneous T-cell lymphoma cells

Article References: Prabhu, K. S., Suleman, M., Habeeba, U., Ahmad, F., Kuttikrishnan, S., Pamiloza Mateo, J. M., Anamangadan, G., Farooqui, A., Salameh, I. M., Bhat, A. A., & Uddin, S. (2026). Bortezomib induces ROS-dependent mitochondrial apoptosis and suppresses SKP2 signaling in cutaneous T-cell lymphoma cells. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-09039-4

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09039-4

Keywords: cutaneous T-cell lymphoma, bortezomib, SKP2, reactive oxygen species, mitochondrial apoptosis, caspases, p21, p27, cisplatin, proteasome inhibitor, glutathione, drug synergy

The findings carry broad implications for male reproductive biology, inflammatory infertility research, and the fundamental question of how a highly specialized cell reprograms or discards the standard machinery of programmed cell death. Spermatozoa are transcriptionally silent cells. Once released from the testis and matured in the epididymis, they can no longer produce new proteins, synthesize DNA, or regulate their own gene expression. This limitation makes them an exceptional model for understanding which components of the apoptotic apparatus survive in a cell that has essentially frozen its molecular inventory.

To investigate how sperm respond to inflammatory conditions, the researchers exposed mature human sperm samples to TNF-α under controlled laboratory conditions and then assessed hallmarks of apoptosis, including phosphatidylserine externalization, mitochondrial membrane potential, caspase activation, and DNA fragmentation. In most somatic cells, binding of TNF-α to TNFR1 initiates a cascade: the receptor trimerizes, recruits the adaptor protein TRADD, and assembles a multiprotein complex known as Complex I. From there, signaling branches toward survival via NF-κB activation or toward death through Complex II and caspase-8, which in turn activates the executioner caspases-3 and -7.

In the sperm cells, however, this cascade appeared to stall at a very early stage. The study found that although TNFR1 is present on the sperm surface and can bind TNF-α, the downstream signaling that normally follows receptor engagement is functionally incomplete. The adaptor proteins required to transmit the death signal are either absent, sequestered, or otherwise nonfunctional in the mature gamete. Without a competent signalosome, the receptor behaves largely as a passive binding site rather than an active trigger of apoptosis.

The authors describe this phenomenon as TNFR1-associated apoptotic resistance. In essence, the receptor’s presence creates a misleading impression: the cell appears equipped to respond to TNF-α, but the molecular wiring behind the receptor has been dismantled during spermiogenesis. This is a biologically coherent outcome. During the dramatic remodeling that converts a round spermatid into a streamlined sperm cell, most of the cytoplasm is discarded, along with the organelles and protein pools that somatic cells rely upon for signaling. What remains is a compact, highly specialized cell optimized for delivery of the paternal genome, not for orchestrating complex signaling conversations with its environment.

Importantly, the resistance was not absolute or indiscriminate. The researchers found that sperm could still undergo forms of cell death, but these appeared to proceed through pathways that do not depend on the canonical TNFR1-driven route. Mitochondrial dysfunction, oxidative stress, and membrane damage can all compromise sperm function and viability, and these stressors operate independently of the receptor pathway. The distinction matters clinically: it suggests that inflammatory conditions rich in TNF-α, such as those seen in male reproductive tract infections, may impair fertility through mechanisms other than classic apoptosis, for example by damaging membranes, disrupting the acrosome, or generating reactive oxygen species.

The implications extend to assisted reproduction as well. Semen processing techniques, sperm selection methods, and culture conditions all expose gametes to variable inflammatory and oxidative environments. Understanding that mature sperm are intrinsically resistant to TNF-α-mediated apoptosis clarifies why simply bathing sperm in inflammatory cytokines does not selectively eliminate damaged cells through this route, a consideration that could inform future sperm selection strategies designed to enrich for the healthiest subpopulations. If TNFR1 signaling is inert, then therapeutic or diagnostic approaches that assume its functionality in sperm need to be reconsidered.

From an evolutionary perspective, apoptotic resistance in the mature gamete raises fascinating questions. On one hand, insensitivity to inflammatory death signals could protect sperm during their transit through tissues that are sometimes inflamed, allowing them to reach the oocyte even under hostile conditions. On the other hand, some scientists have argued that apoptosis-like changes in sperm serve as a quality control mechanism, marking defective cells for removal. The new findings suggest that this quality control, if it exists in mature sperm, does not operate through the TNFR1 axis, pointing instead to other regulators that remain to be fully characterized.

The study also adds to a growing literature on death receptor signaling in germ cells. Earlier work established that immature germ cells express functional death receptors and can respond to Fas ligand and TNF family cytokines, and that this responsiveness diminishes as cells mature. The present work sharpens that picture by demonstrating, with modern flow cytometric, biochemical, and functional assays, that the block in mature sperm occurs at the level of receptor-proximal complex assembly rather than at the death execution machinery itself. In other words, some executioner components persist in the gamete, but the ignition switch that would engage them has been disconnected.

Looking ahead, the researchers suggest several directions for follow-up work. Characterizing exactly which adaptor proteins are lost or inactivated during spermiogenesis, determining whether any residual TNFR1 signaling influences sperm motility or fertilization capacity through non-apoptotic routes, and testing whether similar resistance mechanisms operate in sperm of other species are all natural next steps. There is also therapeutic potential: if the mechanisms that confer apoptotic resistance can be understood in molecular detail, they might inspire strategies to protect somatic cells from inflammatory death in conditions such as sepsis or neurodegeneration, or conversely, to sensitize unwanted cells to TNF-α. For now, the study stands as an elegant demonstration that even the most fundamental programs of cell biology are not universal, and that the human spermatozoon, in its stripped-down simplicity, has rewritten the rules of the death receptor pathway to suit its singular purpose.

Subject of Research: TNFR1-mediated apoptotic resistance in mature human spermatozoa exposed to TNF-α

Article Title: TNFR1-associated apoptotic resistance in mature human spermatozoa under TNF-α exposure

Article References: Barbonetti, A., Tonni, C., Donatelli, V., Castellini, C., Moretto, C., Tienforti, D., Augello, F. R., Cinque, B., & Palumbo, P. (2026). TNFR1-associated apoptotic resistance in mature human spermatozoa under TNF-α exposure. Cell Death Discovery. https://doi.org/10.1038/s41420-026-03355-w

Image Credits: AI Generated

DOI: 10.1038/s41420-026-03355-w

Keywords: TNFR1, TNF-α, apoptosis, human spermatozoa, male fertility, Cell Death Discovery, death receptor signaling, sperm selection, inflammatory cytokines, spermiogenesis, caspases, assisted reproduction

The research, published in Annals of Hematology, took a direct approach to a question that has lingered at the edge of AML biology for years. Rather than inferring apoptotic behavior from broad molecular signatures, the team prospectively measured messenger RNA expression of apoptosis-related genes in bone marrow mononuclear cells from 90 patients with newly diagnosed AML. Every sample came from patients at the start of their treatment journey, before therapy could reshape the transcriptional landscape of their leukemia. That design choice matters, because it allowed the investigators to ask whether the apoptotic wiring present at diagnosis could predict what happened next — how long patients lived, how they responded to treatment, and whether their disease returned.

When the researchers clustered patients according to their apoptosis gene expression profiles, two biologically distinct groups emerged, and the differences between them were striking. The first cluster carried a transcriptional pattern that, on its surface, looked almost reassuring: relatively higher expression of the classic anti-apoptotic gene BCL2, the very gene targeted by one of modern hematology’s most celebrated drugs. The second cluster told a more complicated story. These patients showed coordinated upregulation of a battery of pro-apoptotic genes, including BCL2L11 (better known as BIM), BBC3 (PUMA), BID, BAD, BIK, and BAX — genes whose protein products are supposed to push cells toward self-destruction. At the same time, the cells appeared to shift their survival strategy away from BCL2 and toward alternative anti-apoptotic regulators, with increased expression of MCL1 and BCL2L1, which encodes the survival protein BCL-xL.

That combination — more pro-death genes, but a survival apparatus rebuilt around different guardians — might seem paradoxical, and the clinical outcomes made the paradox impossible to ignore. Patients in the second cluster had significantly inferior overall survival. The researchers also observed reduced expression of CASP3 and CASP7, the executioner caspases that carry out the final, irreversible steps of apoptosis, in this high-risk group. Lower levels of these molecular executioners, the authors suggest, may mean that even when the death signal is triggered, the cell’s machinery for completing the process runs less efficiently. In other words, the leukemic cells of Cluster 2 patients appeared to be shouting the commands for self-destruction while simultaneously dismantling the equipment needed to obey them.

The timing of the study gives its findings particular weight. The treatment of AML has been transformed in recent years by venetoclax, a BCL2 inhibitor that, when combined with the hypomethylating agent azacitidine — a regimen known as VenAza — has become a backbone of therapy for older patients and those unfit for intensive chemotherapy. Venetoclax works by neutralizing BCL2, removing one of the main shields that leukemic cells use to resist apoptosis. If a patient’s leukemia depends heavily on BCL2, the drug should work well. If the cells have quietly reorganized their survival machinery around MCL1 or BCL-xL, the drug’s leverage diminishes. The Lodz team’s data fit that logic with unsettling precision: among patients treated with venetoclax plus azacitidine, those in Cluster 2 demonstrated significantly shorter event-free survival.

The biological features of Cluster 2 help explain why. The researchers noted that this subgroup displayed a monocytic immunophenotype, a characteristic that previous studies had already associated with reduced sensitivity to BCL2-targeted therapy. Monocytic AML cells tend to rely more on MCL1 and other alternative survival proteins than on BCL2 itself, making venetoclax a less effective key for that particular lock. Combined with the transcriptional evidence of increased MCL1 and BCL-xL expression and diminished executioner caspase activity, the picture that emerges is of a leukemia subtype that is not merely more aggressive, but differently engineered — one whose apoptotic architecture is fundamentally less vulnerable to the therapies now widely deployed against it.

Then comes the study’s most provocative single finding. When the researchers examined individual genes rather than cluster-level patterns, one stood out: BIK. Higher BIK mRNA expression was associated with poorer survival and with a lack of response to venetoclax-azacitidine therapy, and the association held up as an independent prognostic marker. The paradox here is sharp. BIK is a pro-apoptotic gene, a member of the BH3-only family whose role is to help tip cells into death. Higher expression of a death-promoting gene should, intuitively, be good news. Instead, in this cohort, it flagged the patients most likely to fare badly. The authors highlight this paradoxical association explicitly, and it serves as a reminder that gene expression in cancer rarely obeys simple intuition — context, coordination, and the surrounding molecular machinery determine whether a signal means surrender or defiance.

Why might high BIK expression accompany worse outcomes? The study’s cluster-level data suggest a plausible framework. In Cluster 2, BIK is upregulated alongside a host of other pro-apoptotic genes as part of a broader transcriptional state, one in which the cell simultaneously bolsters alternative survival pathways through MCL1 and BCL-xL and dampens the caspase machinery that would finalize apoptosis. In that setting, elevated BIK may be less a weapon than a distress signal — a marker of a cellular state in which death pathways are chronically activated yet chronically thwarted. Cells locked in such a standoff may be under persistent stress, and stress-adapted leukemic cells are often the most difficult to eradicate. BIK expression, on this reading, is not causing the poor prognosis but faithfully reporting it, which is precisely what a good biomarker should do.

The clinical implications ripple outward in several directions. First, the study demonstrates that apoptosis-related gene expression, measured at diagnosis, defines clinically distinct AML subgroups — a finding that could eventually inform how patients are risk-stratified beyond the current arsenal of cytogenetic and mutation-based markers. Second, the link between Cluster 2 biology and shortened event-free survival on venetoclax-azacitidine raises the possibility that expression profiling of apoptotic genes could help identify, upfront, which patients are unlikely to benefit from the regimen and might be better served by alternative or combination strategies, including agents targeting MCL1 that are currently in development. Third, the independent prognostic value of BIK offers a concrete, testable candidate for prospective validation in larger and more diverse cohorts.

Cautious interpretation remains essential. The cohort comprised 90 patients treated at a single center, and the findings, while internally coherent, will need replication before they reshape clinical practice. The authors themselves frame the results as demonstrating that dysregulation of apoptosis-related gene expression defines clinically distinct subgroups and may contribute to differences in prognosis and therapeutic response — a claim about mechanism and association rather than a prescription for immediate changes in care. Yet the conceptual shift the study proposes is substantial. AML has traditionally been classified by the mutations its cells carry; this work argues that how those cells manage life and death — the balance of pro- and anti-apoptotic forces, the choice of survival protein, the integrity of the caspase execution machinery — is itself a meaningful axis of disease biology. If subsequent studies confirm the pattern, the humble measurement of apoptosis gene mRNA could become a routine part of the diagnostic conversation, and the paradoxical signal from BIK could stand as a symbol of how much remains to be learned about why some leukemias die on command and others simply will not.

Subject of Research: Apoptosis-related gene expression profiling in acute myeloid leukemia and its association with patient clustering, prognosis, and response to venetoclax-based therapy

Article Title: Apoptosis gene expression analysis identifies biologically distinct AML clusters and BIK as an independent prognostic marker

Article References: Strzałka, K., Strzałka, P., Jarych, D., Wiśnik, A., Mikulski, D., Kościelny, K., Czemerska, M., Zawlik, I., Wierzbowska, A., & Pluta, A. (2026). Apoptosis gene expression analysis identifies biologically distinct AML clusters and BIK as an independent prognostic marker. Annals of Hematology. https://doi.org/10.1007/s00277-026-07268-7

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07268-7

Keywords: acute myeloid leukemia, apoptosis, gene expression profiling, BIK, venetoclax, azacitidine, BCL2, MCL1, prognostic marker, drug resistance, caspases, hematology