The molecular mechanisms linking immune cell signaling to osteoclastogenesis remain incompletely defined. Here, we identify an Annexin A1 (AnxA1)-Dectin-1 axis as a key driver of osteoclast differentiation. Dectin-1 (CLEC7A), a myeloid C-type lectin receptor best known for β-glucan recognition, is shown to bind the endogenous ligand AnxA1 on pre-osteoclasts, thereby promoting their maturation. In Dectin-1 deficient mice, reduced osteoclast numbers resulted in increased bone volume, whereas β-glucan-induced Dectin-1 activation enhanced osteoclastogenesis. Within the bone marrow niche, AnxA1 was abundantly expressed on B220+ B cells, and γ-irradiation markedly increased its surface translocation both in vitro and in vivo. γ-irradiated B220+ B cells exhibited strong Dectin-1 binding capacity and robustly stimulated osteoclast differentiation in a Dectin-1-dependent manner. These findings establish the AnxA1-Dectin-1 interaction as a critical immune-skeletal communication pathway, revealing a mechanism by which radiation exposed immune cells can accelerate bone resorption. Targeting this axis offers a potential strategy to mitigate radiation-induced bone degradation and preserve skeletal homeostasis.

PURPOSE:To determine the benefit, measured as complete removal of a tumor so that no tumor cells are detectable during histopathologic examination of the resection margin (R0 resection rate), of induction chemotherapy plus chemoradiotherapy (CRT) compared with chemotherapy alone for unresectable pancreatic tumors. PATIENTS AND METHODS:CONKO-007, an investigator-initiated open-label, multicentric, phase III randomized clinical trial, enrolled 525 patients with unresectable tumors, and 495 patients received induction chemotherapy (402 with fluorouracil, irinotecan, and oxaliplatin [FOLFIRINOX] and 93 with gemcitabine). Patients without progression after 3 months of induction chemotherapy (n = 336) were randomly assigned for continuation of the same chemotherapy (n = 167) or CRT (n = 169; 50.4Gy concurrently with gemcitabine). Resectability was centrally reassessed by a panel of surgeons. Surgery was recommended if possible. After an interim analysis, the primary end point was changed from overall survival (OS) to overall R0 resection rate because of slow recruitment. The median follow-up was 76 months. Important planned secondary end points were R0 resection rate in the surgically treated population and OS. RESULTS:The primary end point (overall R0 resection rate) was not significantly different between treatment arms with 25% (43 of 169) in the CRT arm versus 18% in the chemotherapy arm (30 of 167; P = .113). Secondary end point analysis showed that surgery was performed equally often (P = .91); R0 resection rate in patients who underwent surgery was higher after CRT, 69.4% (43 of 62) compared with chemotherapy alone: 50.0% (30 of 60 patients, P = .04). Other parameters of resection (ratio of R0/R1/R2/no resection) also favored CRT (P = .02). No difference in OS was seen between treatment arms (hazard ratio [HR], 0.937 [95% CI, 0.747 to 1.174]; P = .57; randomly assigned intention-to-treat patients). Surgery was associated with longer OS (P < .001, HR, 0.525 [95% CI, 0.408 to 0.676]). CONCLUSION:Although not improving overall R0 resection rate or survival, CRT enables a R0 resection in surgically treated patients more often than chemotherapy alone.

Background Even in the area of immune therapies, multimodal treatment of head and neck squamous cell carcinoma (HNSCC) is a big challenge. Small molecule kinase inhibitors (smKI), that target the DNA damage repair (DDR) system, have been described to alter, in addition to their radio-sensitizing effects, the immune phenotype of HNSCC. Thereby, the ATM and ATR kinases are key mediators of the DDR. However, the consequences these changes of the tumor cell phenotype have on immune cells are still poorly understood. Consequently, we here investigated how single and combination treatment of HNSCC cells with an ATM (ATMi) or an ATR inhibitor (ATRi) in combination with hypo-fractionated radiotherapy (RT) differently affects the activation of human cytotoxic CD8 + T cells regarding proliferation, activation marker surface expression and cytokine secretion. Methods Human papillomavirus (HPV)-negative (Cal-33, HSC4) and HPV-positive (UM-SCC-47, UD-SCC-2) HNSCC tumor cells were treated with hypo-fractionated RT of 2 x 5 Gray (Gy) in combination with AZD0156 (ATMi) or VE-822 (ATRi) and co-cultured with human CD8 + T cells for 96 h. T cell activation was quantified by CFSE-signal detected proliferation rates, activation marker expression on surfaces of the T cells, and by secretion of interferon gamma (IFN-γ) in the supernatants of the co-cultures via ELISA. Results In 2D co-cultivation settings RT-, HPV-status- and inhibitor-dependent influences on Tcell activation were observed. Thereby, a stronger activation of T cells could be achieved after co-cultivation with ATRi-treated HNSCC tumor cells compared to ATMi. However, the addition of immune checkpoint inhibitors did not lead to enhanced T cell activation. In 3D co-cultures, a shift from RT-induced to a more inhibitor-induced effect on human T cells was visible and confirmed the superiority of ATRi, especially in combination with additional RT. Conclusion The combination of RT + ATRi resulted in increased T cell activation compared to the combined treatment with ATMi, respectively. This suggests an advantage of ATRi in comparison to ATMi in combination with RT for induction of beneficial anti-tumor immune responses in HNSCC.

[This corrects the article DOI: 10.3389/fonc.2025.1695468.].

The local immune effects of cancer radiotherapy remain poorly characterized in humans due to limited access to irradiated tissue. Mechanistic insights largely derive from preclinical models employing tumor-intact, neoadjuvant-like settings. Here, we present real-world immunoprofiling data from breast cancer patients undergoing breast-conserving surgery with (n = 20) or without (n = 29) intraoperative radiotherapy (IORT). Postoperative wound fluid samples were analyzed by flow cytometry, multiplex cytokine profiling, and bulk RNA-sequencing, alongside systemic immune monitoring in peripheral blood. IORT triggered rapid local accumulation of distinct innate immune cell subsets and cytokines mediating recruitment, activation, and innate-adaptive crosstalk, accompanied by systemic features consistent with emergency hematopoiesis. Transcriptomic profiling of wound fluid mononuclear cells revealed enrichment of proinflammatory IL-6-JAK/STAT3 signaling. In vitro, irradiation of primary breast tissue cells recapitulated key cytokine patterns and led to robust senescence induction, suggesting irradiated, senescent normal tissue cells as drivers of early immune activation in postsurgical radiotherapy. These data provide direct clinical evidence that radiotherapy shapes local and systemic immune responses, offering mechanistic insights with clear relevance for tumor immunology and the development of rational radiotherapy‒immunotherapy combination strategies.

Neoadjuvant therapies incorporating immune checkpoint inhibitors (ICIs) have shown promise in locally advanced head and neck squamous cell carcinoma (HNSCC). However, biomarkers for pathological complete response (pCR) remain undefined. In the CheckRad-CD8 trial (NCT03426657), we performed RNA sequencing on pre- and post-treatment biopsies from 77 locally advanced HNSCC patients treated with induction chemoimmunotherapy. Of these, 42 patients achieved pCR, while 35 had residual disease (RD). Differentially expressed genes (DEGs) and pathways were identified using DESeq2 and gene set enrichment analysis. Tumor immune microenvironment analysis, utilizing eight RNAseq deconvolution methods, assessed 266 gene signatures and 38 curated immunotherapy signatures. Baseline intratumoral CD8+ T-cell density, stromal tumor lymphocyte infiltration, and combined PD-L1 proportion score were associated with pCR. Pretreatment analysis identified 830 DEGs between pCR and RD, with T and B-cell-related pathways enriched in pCR samples. Logistic regression models indicated the significance of T and B cells and IFN-gamma signaling in predicting pCR. Furthermore, a new CheckRad-7-gene signature, with an AUC of 0.902 in the training cohort, effectively predicted pCR and survival, serving as a robust biomarker for prognosis and treatment response in HNSCC.

Low dose radiation therapy (LDRT) is commonly applied for its pain and symptom-relieving effects in the treatment of different benign diseases, such as chronic degenerative and inflammatory, or hyperproliferative disorders. Most clinical trials report a beneficial therapeutic effect of LDRT and further, robust preclinical evidence on the biological modes of action of LDRT is existent. In chronic degenerative and inflammatory diseases such as osteoarthritis, LDRT can ameliorate inflammatory processes and impacts positively on the bone metabolism. A key mechanism is the modulation of the endothelium and the phenotype of macrophages. In the bone, the deposition of new bone matrix is supported, while bone degradation is diminished. In hyperproliferative disorders, the main mode of action is the inhibition of the differentiation and proliferation of fibroblasts and myofibroblasts, along with a modulation of inflammatory mediators, such as cytokines. Even though comprehensive preclinical evidence supports the use of LDRT, biological mechanistic insights from randomized clinical trials is mostly missing for LDRT and indicates a significant translational gap. Apart from preclinical data, the evidence for LDRT is based largely on observational clinical trials, with only limited randomized and placebo-controlled trials available. In the future, rigorously designed randomized disease-specific studies with standardized protocols, translational research programs and objectifiable clinical and biological endpoints are needed to establish LDRT as precise and evidence-based therapy.

Background and purpose Glioblastoma is the most aggressive malignant brain tumor with an overall poor prognosis despite advanced chemoradiation approaches. Immunotherapeutic strategies have not been beneficial to date. Even being present only at low level in the brain, dendritic cells (DCs) have the potential to promote anti-tumor immune responses. In this study we aimed to gain insight into the interactions between glioblastoma tumor cells, DCs and T cells to understand the molecular and cellular mechanisms driving immune alterations in glioblastoma during standard treatments for optimizing immune therapies in the future. Material and methods Impact of the conventional chemoradiation (RCT) treatment scheme of glioblastoma cells on conventional DCs type 1 and 2 (cDC) was tested in a syngeneic murine cell culture setting. GL261-luc2 glioblastoma cells were treated and subsequently co-cultured with cDC1-like and cDC2-like cells. Their immunological status was determined as follows: Expression of activation and immune checkpoint markers was quantified via flow cytometry. Cytokine and chemokine secretion was measured by bead-based immunoassays. Mixed lymphocyte reactions with either CD4+ or CD8+ T cells were performed to determine the potential of cDCs in stimulating T cell proliferation. Results The cellular contact of cDC1-like cells with RCT-treated glioblastoma cells shifted their immune phenotype to a more activated one, whereas the activation of cDC2-like cells was limited. Furthermore, the extracellular profile of inflammatory and immunoregulatory cytokines and chemokines was highly dependent on the tumor cell treatment scheme in co-culture with cDC1-like cells, with the most pronounced effect after RCT. These modifications in the activation status of cDC1- and cDC2-like cells after tumor cell contact subsequently resulted in significantly enhanced CD8+ and CD4+ T cell proliferation. Conclusion Current glioblastoma cell treatment impacts on the subsequent activation of cDCs and T cells and should serve as basis for improving immunotherapeutic strategies of brain tumors.