The research, led by Kamila Maliszewska-Olejniczak of Warsaw University of Life Sciences together with colleagues at the Nencki Institute of Experimental Biology and the National Centre for Nuclear Research in Poland, examined how deleting the large-conductance calcium-activated potassium channel, known as BKCa, alters the way glioblastoma cells respond to ultra-high dose rate electron irradiation. This irradiation regime is the laboratory cousin of FLASH radiotherapy, an emerging modality that delivers radiation at dose rates exceeding 40 Gy per second in millisecond bursts. Preclinical work has repeatedly suggested that FLASH delivery spares normal tissue while preserving tumor kill, a phenomenon called the FLASH effect, thought to involve transient oxygen depletion and reduced reactive oxygen species chemistry. Yet the underlying biology remains stubbornly unclear, and the new findings suggest that ion channels may be part of the answer.

BKCa channels are not passive bystanders in glioblastoma. They are overexpressed in established cell lines such as U87MG and T98G, in glioblastoma stem-like cells, and in primary cells from patient biopsies, and a glioma-specific splice variant called gBKCa is highly expressed in the disease. These so-called oncochannels support migration and invasion by driving the ion and water efflux needed for cell shrinkage during movement, and they are functionally upregulated under hypoxia, contributing to chemoresistance. Crucially, a mitochondrial isoform, mitoBKCa, helps govern mitochondrial function and oxidative stress, and previous work by the same group showed that its loss elevates mitochondrial reactive oxygen species in U87MG cells. Because ionizing radiation acts largely through oxidative chemistry, the team hypothesized that BKCa deletion might reshape the cellular response to ultra-high dose rate beams.

To test this, the researchers used CRISPR-Cas9 genome editing to generate U87MG cells lacking the pore-forming alpha subunit encoded by KCNMA1, then exposed both wild-type and knockout cells to a 9 MeV electron beam delivered by a modified intraoperative linear accelerator operating in FLASH mode at an average dose rate of 150 Gy per second, with total irradiation times under 40 milliseconds. Doses of approximately 2, 3 and 5 Gy were verified with radiochromic film and a real-time inductive dosimetry system, with flasks positioned in a slab phantom under ambient oxygen conditions. The team then interrogated the cells with a comprehensive battery of assays: clonogenic survival, fluorescence-based ROS measurement, BrdU-DAPI cell-cycle analysis, Annexin V and propidium iodide staining, PARP1 cleavage detection, the alkaline comet assay, gamma-H2AX flow cytometry, 53BP1 immunofluorescence, quantitative PCR for fourteen DNA repair genes, and Western blotting.

The first surprise was what did not change. Clonogenic survival, the gold-standard endpoint of radiobiology, declined dose-dependently in both cell lines, from full survival in untreated controls to roughly 27 percent at 5 Gy in wild-type cells and about 35 percent in knockout cells, but the differences between genotypes were not statistically significant at any dose. Deleting BKCa, in other words, did not make the cells more resistant or more sensitive in terms of long-term colony-forming capacity. Yet beneath this deceptively calm surface, the molecular machinery was behaving very differently. Knockout cells accumulated significantly more reactive oxygen species after 3 Gy, reaching levels of 4.66 relative units compared with 2.21 in wild-type cells, consistent with the idea that the channel helps maintain mitochondrial redox homeostasis and that its absence leaves cells more vulnerable to radiation-induced oxidative stress.

The cell-cycle response also diverged sharply. Thirty minutes after irradiation, wild-type cells distributed themselves across G0/G1, S and G2/M phases, whereas the knockout cells piled up dramatically in G0/G1, reaching nearly 75 percent of the population compared with about 48 percent in irradiated wild-type cells. Notably, the genotoxic chemotherapeutic etoposide produced a classic G2/M arrest in both lines, showing that the two cell lines respond differently to distinct forms of DNA damage and that the G0/G1 accumulation is a specific feature of the ultra-high dose rate response in channel-deficient cells. The authors caution that their data do not establish a direct causal mechanism linking BKCa deletion to this checkpoint redistribution, and that future work on specific checkpoint regulators will be needed.

Cell death signaling told a subtler story. Both cell lines showed reduced viability and increased early apoptosis after irradiation, but without significant differences between genotypes. Cleaved PARP1, a caspase-generated marker of apoptotic signaling, rose significantly in knockout cells but not in wild-type cells, although the between-genotype comparison did not reach significance and Western blotting of the cleaved-to-full-length PARP1 ratio showed no genotype-dependent difference. The most striking finding, however, concerned DNA damage signaling itself. Despite suffering comparable or greater DNA strand damage, as confirmed by the alkaline comet assay with tail DNA rising to more than 80 percent in irradiated knockout cells, the knockout cells accumulated far less gamma-H2AX, the phosphorylated histone that marks double-strand breaks, reaching only about 24 percent positive cells versus nearly 70 percent in irradiated wild-type cells. Formation of 53BP1 foci, which recruit repair complexes to damaged chromatin and bias repair toward non-homologous end joining, was likewise significantly reduced in the knockout cells.

The authors are careful to stress that reduced gamma-H2AX and 53BP1 should not be read as an absence of DNA damage. The comet assay proves the damage is there. Rather, the findings point to impaired damage recognition and altered assembly of repair complexes, a dysregulation of the early DNA damage response rather than a reduction in the insult itself. This interpretation is reinforced by the transcriptional data. Irradiated knockout cells upregulated double-strand break repair genes including ATM, BRCA1 and RAD51 relative to irradiated wild-type cells, while simultaneously downregulating single-strand break repair genes dependent on PARP enzymes, including PARP1, PARP2, PARP3 and XRCC1. The team had previously implicated BKCa as a regulator of the DNA damage response under oxidative stress caused by particulate matter exposure, and the new results extend that concept to ionizing radiation delivered at ultra-high dose rates.

The study has clear limitations that the authors acknowledge candidly. All experiments used a single isogenic U87MG model in vitro, so validation in additional cell lines and patient-derived glioblastoma models is essential, and no conventional dose-rate control was included, meaning the observed effects cannot be attributed specifically to the FLASH effect as opposed to the irradiation conditions used. Nevertheless, the work identifies BKCa as a genuine modulator of the early molecular response of glioblastoma cells to ultra-high dose rate irradiation, spanning redox balance, cell-cycle distribution, DNA damage signaling, apoptotic markers and repair gene transcription. Given that potassium channels can be targeted pharmacologically or genetically, the findings open a plausible path toward combining channel modulation with FLASH radiotherapy and temozolomide, although the authors emphasize that the present data provide no evidence yet of BKCa-dependent radiosensitization. As clinical FLASH trials accelerate, understanding which molecular levers distinguish tumor from normal tissue responses may prove decisive, and this study suggests that an ion channel once studied mainly for its role in cell migration may be one of those levers.

Subject of Research: How BKCa potassium channel deletion modulates the DNA damage response of glioblastoma cells to electron ultra-high dose rate irradiation

Article Title: BKCa channel deletion modulates the DNA damage response to electron ultra-high dose rate irradiation in glioblastoma cells

Article References: Maliszewska-Olejniczak, K., Fryc, M., Kustra, A., Wiktorska, K., Lenartowicz-Gasik, A., Soroka, W., Rzadkiewicz, J., Żochowska, M., Kulawiak, B., & Bednarczyk, P. (2026). BKCa channel deletion modulates the DNA damage response to electron ultra-high dose rate irradiation in glioblastoma cells. Journal of Neuro-Oncology, 179(3), Article 95. https://doi.org/10.1007/s11060-026-05804-z

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05804-z

Keywords: glioblastoma, BKCa channel, FLASH radiotherapy, ultra-high dose rate irradiation, DNA damage response, gamma-H2AX, 53BP1, reactive oxygen species, U87MG cells, apoptosis, DNA repair, ion channels

The clinical context makes the urgency clear. For decades, randomized trials of adjuvant chemoradiotherapy after pancreatic surgery, including landmark studies from the European Study Group for Pancreatic Cancer and the RTOG, have produced conflicting or marginal survival benefits. More recent trials such as PREOPANC and PREOPANC-2 have tested neoadjuvant chemoradiotherapy against chemotherapy-first strategies, with results that have done little to resolve the controversy. Meanwhile, the LAP07 and CONKO-007 trials failed to demonstrate clear survival advantages for adding radiation in locally advanced disease. The authors argue that these disappointments reflect a deeper problem: conventional radiotherapy was designed and optimized purely as a cytotoxic tool, with little attention to how radiation doses, fractionation schedules, target volumes and delivery techniques shape the immune microenvironment of the tumor.

The immunological rationale for combining radiation with immunotherapy rests on a growing body of preclinical evidence. Radiation can kill cancer cells in ways that release tumor antigens and danger signals, triggering what is known as immunogenic cell death. This process can recruit and activate dendritic cells, which carry tumor antigens to lymph nodes and prime CD8-positive T cells capable of recognizing and destroying malignant cells throughout the body, including at sites never directly irradiated. This systemic effect, called the abscopal response, has long been considered rare and unpredictable. But work from multiple laboratories, including studies of the DNA exonuclease Trex1 and the cGAS-STING DNA sensing pathway, has revealed that whether radiation stimulates or suppresses immunity depends exquisitely on dose, fractionation and timing, parameters that clinicians have historically chosen without immunological consideration.

Pancreatic cancer presents unique obstacles to this strategy. The disease is characterized by an exceptionally immunosuppressive tumor microenvironment, dominated by dense stromal desmoplasia, cancer-associated fibroblasts, immunosuppressive macrophages, myeloid-derived suppressor cells and regulatory T cells that collectively exclude or exhaust cytotoxic lymphocytes. The tumor’s low mutation burden limits the availability of neoantigens that could be recognized by the immune system. Landmark clinical trials of checkpoint inhibitors in pancreatic cancer, including ipilimumab as a single agent, the durvalumab and tremelimumab combination, and the PRINCE and CCTG PA.7 studies of immunotherapy added to chemotherapy, have all failed to deliver meaningful survival improvements outside the rare subset of patients with microsatellite instability. The authors stress that this track record does not mean immunotherapy is hopeless in pancreatic cancer, but rather that checkpoint blockade alone cannot overcome the disease’s profound immune barriers without complementary interventions.

Here, radiotherapy could serve as the missing catalyst. Preclinical studies in pancreatic cancer models have shown that radiation can increase tumor infiltration by effector T cells, polarize tumor-associated macrophages toward pro-inflammatory phenotypes, and enhance the efficacy of checkpoint blockade, CD40 agonist antibodies, and even CAR T cell therapies directed against targets such as mesothelin and claudin 18.2. Radiation conditioning has been shown to mitigate antigen escape in CAR T cell approaches, and low-dose irradiation can reprogram macrophage differentiation in ways that support T cell function. These findings suggest that radiation, delivered with the right parameters, could transform a cold, immune-excluded pancreatic tumor into one that is susceptible to systemic immunotherapy.

Crucially, the authors emphasize that the details of radiation delivery matter enormously. Preclinical work has demonstrated that ablative stereotactic doses, conventional fractionation, and hypofractionated schedules each produce distinct immunological fingerprints. High single doses may trigger the Trex1-mediated degradation of cytosolic DNA, actually blunting the interferon response that drives antitumor immunity, whereas certain fractionated schedules preserve and amplify cGAS-STING signaling. The sequencing of immunotherapy relative to radiation also matters: studies have shown that the timing of PD-1 blockade relative to tumor irradiation determines whether abscopal responses are induced. Emerging technologies such as magnetic resonance-guided adaptive radiotherapy, FLASH ultrahigh dose-rate irradiation, pulsed low-dose-rate techniques, proton and carbon ion therapy, and spatially fractionated approaches offer clinicians an expanding toolkit for sculpting the immunological consequences of each radiation session.

The article also highlights next-generation immunotherapeutic partners that may prove more suitable than conventional checkpoint inhibitors for combination with radiation in pancreatic cancer. Personalized mRNA neoantigen vaccines have already demonstrated the ability to expand tumor-specific T cells in resected pancreatic cancer patients, and mutational KRAS-targeted vaccine strategies combined with dual checkpoint blockade have shown encouraging results in early trials. Agonist CD40 antibodies capable of activating antigen-presenting cells, Toll-like receptor agonists, IL-15 and IL-2 pathway modulators, STING agonists, adenosine pathway blockers such as CD73 and A2A receptor inhibitors, and stromal reprogramming agents including focal adhesion kinase inhibitors and TGF-beta antagonists all represent rational partners. Novel platforms including tumor-targeted cytokines, radiopharmaceuticals, boron neutron capture therapy, and radiotherapy-activated prodrugs that release immune agonists only within irradiated tissue further expand the possibilities for precisely timed, spatially controlled immune activation.

The authors also draw attention to an often-overlooked variable: the tumor-draining lymph nodes and circulating lymphocytes. Elective nodal irradiation, a mainstay of conventional radiotherapy field design, has been shown in preclinical studies to attenuate the combinatorial efficacy of stereotactic radiation and immunotherapy by depleting the very lymphoid structures needed to prime systemic immunity. Radiation-induced lymphopenia, a common toxicity of large-field abdominal irradiation, may undermine the systemic immune benefits of radioimmunotherapy. Newer approaches that minimize exposure of lymphoid organs, preserve lymphatic drainage, and exploit artificial intelligence-guided treatment planning to spare circulating lymphocytes may be essential for unlocking the full potential of combined regimens. Proton therapy, with its reduced exit dose, offers a physically grounded strategy for reducing lymphocyte exposure compared with photon techniques.

Looking forward, the authors propose a decision map for clinical development that incorporates biomarker-guided patient selection, adaptive trial designs, and rational sequencing of optimized radiation backbones with selected immunotherapeutic agents. Advances in radiomics, genomic models of radiation sensitivity, liquid biopsy, and imaging technologies such as FAPI-PET may allow clinicians to identify which patients and which tumors are most likely to respond to specific radioimmunotherapy combinations. Biomarkers of immune activation, including circulating tumor DNA kinetics, immune cell signatures, and imaging features of the tumor microenvironment, could enable real-time adaptation of treatment strategies. The authors argue that progress will depend on moving beyond empirical combinations toward mechanistically informed designs in which every element of the radiation prescription, from dose and fractionation to target volume and delivery modality, is chosen deliberately for its immunological consequences.

Ultimately, the perspective reframes localized pancreatic cancer as a disease that may finally yield to a truly integrated therapeutic approach. Rather than viewing radiotherapy and immunotherapy as competing strategies with individually disappointing track records, the authors make a compelling case that the two modalities, when co-optimized at the level of physics, biology and clinical trial design, could simultaneously improve local tumor control and suppress the micrometastatic disease that drives most deaths from this cancer. With pancreatic cancer projected to become the second leading cause of cancer-related death in the United States by 2040, and with current treatment paradigms delivering only marginal gains, the stakes of getting this combination right could not be higher. The blueprint laid out by Colin and colleagues offers the field a rigorous, immunologically grounded path forward, one that transforms radiation from a purely destructive force into an active partner in mobilizing the patient’s immune system against one of medicine’s most lethal malignancies.

Subject of Research: Combining optimized radiotherapy with next-generation immunotherapy for localized pancreatic ductal adenocarcinoma.

Article Title: Challenges and opportunities in combining radiotherapy and immunotherapy for localized pancreatic cancer

Article References: Colin, G., Streel, S., Deutsch, E., Galluzzi, L., & Foidart, P. (2026). Challenges and opportunities in combining radiotherapy and immunotherapy for localized pancreatic cancer. Nature Reviews Gastroenterology & Hepatology. https://doi.org/10.1038/s41575-026-01250-4

Image Credits: AI Generated

DOI: 10.1038/s41575-026-01250-4

Keywords: pancreatic cancer, radiotherapy, immunotherapy, immune checkpoint blockade, localized pancreatic ductal adenocarcinoma, tumor microenvironment, abscopal effect, immunogenic cell death, stereotactic body radiation therapy, FLASH radiotherapy, biomarker-guided trials, stromal reprogramming