Small cell lung cancer (SCLC) is one of the most aggressive malignancies, characterized by rapid metastatic dissemination and poor overall survival. Despite harboring excessive alterations, expectedly resulting in immunogenic neoantigens, patients with SCLC remain largely refractory to immunotherapy. We found abundant frameshift mutations in SCLC, regarded as highly immunogenic, counterbalanced by a hyperactive nonsense-mediated decay (NMD) pathway, responsible for frameshift-mRNA degradation. NMD activity correlated with tumor mutational burden (TMB) across cancers, suggesting that SCLC and other TMBhigh cancers may depend on NMD to limit the accumulation of mutation-derived byproducts in order to maintain cellular homeostasis and evade immune recognition. In TMBhigh SCLC models, inhibition of NMD impaired cell proliferation and induced ER stress-dependent apoptosis due to the accumulation of misfolded proteins. Genetic and pharmacological NMD inhibition in vivo effectively controlled TMBhigh tumor growth without overt toxicity. By integrating genome and transcriptome sequencing with MHC-I immunopeptidomics and functional in vitro and in vivo assays, we identified that NMD inhibition boosted neoantigen expression and presentation by tumor cells and increased T cell recognition, thus enhancing overall tumor immunogenicity and further improving immunotherapy efficacy in vivo. Our work shows that SCLC – as a TMBhigh cancer – relies on NMD for survival and immune escape, uncovering a novel TMB-dependent tractable vulnerability for this devastating disease.

Physicochemical properties of CDRH3s and VH gene segment mutation frequencies

Trophoblast cell surface antigen 2 (TROP2) is a glycoprotein expressed on epithelial tumor cells and therefore an established target for antibody-drug conjugates (ADCs). Epstein-Barr virus (EBV)-positive gastric cancer is a molecularly distinct subtype characterized by unique immunological features, including frequent responsiveness to immune checkpoint inhibitors (ICIs). Nevertheless, a subset of these patients fails to benefit from ICI therapy, leaving an unmet need for non-immunotherapeutic treatment options. Tumors lacking TROP2, fail to respond to TROP2-directed ADCs. We therefore assessed the prevalence of TROP2 expression in gastric cancer including the EBV-positive subtype, which has not been characterized to date. TROP2 expression was evaluated by immunohistochemistry in 525 patients with gastric cancer classified according to TCGA molecular subtypes, representing the largest Caucasian cohort assessed for TROP2 to date. TROP2 expression differed significantly across molecular subtypes (p < 0.01), with EBV-positive tumors showing the highest median expression (H-score 150). Complete absence of TROP2, the expression pattern associated with treatment failure, was observed in only 3.7% of EBV-positive tumors, compared with 18.8% of chromosomal instability, 25.4% of genomically stable, and 36.2% of microsatellite instability tumors. Nearly all EBV-positive gastric cancers therefore express TROP2 at levels compatible with ADC targeting. These findings identify TROP2 as a target in EBV-positive gastric cancer and provide a rationale for clinical investigation of TROP2-directed ADCs in this molecularly defined population, particularly as a non-immunotherapeutic option for patients who fail ICI therapy.

Supplementary Figure S2: Kaplan-Meier statistics on median real-world overall survival (rwOS) in different subgroups

Small cell lung cancer (SCLC) is a highly aggressive cancer with one of the highest tumor mutational burden (TMB), but patients show only limited response to immunotherapy. The nonsense-mediated decay (NMD) pathway is responsible for the degradation of mutant transcripts thereby enabling tumors to cope with somatic alterations and contributing to immune evasion. We therefore hypothesized that inhibition of NMD in TMBhigh tumors such as SCLC may disrupt cellular homeostasis while promoting anti-tumor immunity. We have profiled the mutational landscape of >400 SCLC patients and generated >100 patient-derived xenotransplant models. Analysis of NMD activity in our SCLC cohort and across all cancers within the TCGA revealed a hyperactive NMD pathway in SCLC and other TMBhigh tumors, suggesting that an increased NMD efficiency may be required to cope with such an elevated mutational load. Inhibition of NMD in SCLC led to a massive accumulation of faulty transcripts resulting in cell cycle arrest and ER stress-dependent apoptosis, with the degree of cell death vulnerability correlating with the samples’ TMB. Accordingly, non-neoplastic cells and TMBlow tumors exhibited greater tolerance to NMD inhibition, whereas induction of hypermutation in TMBlow tumors rendered them susceptible to NMD inhibition, supporting a potential therapeutic index for in vivo treatment. Pharmacological NMD inhibition in immunocompromised mice successfully decreased tumor growth of TMBhigh tumors without overt toxicity, demonstrating for the first time a tumor-specific cell-autonomous vulnerability to NMD inhibition. We furthermore evaluated neoantigen expression and presentation after NMD inhibition in SCLC. Genome sequencing followed by transcriptome sequencing and HLA-I-binding modeling predicted an upregulation of hundred-thousands of neoantigens per sample upon NMD inhibition. HLA-I ligandomics revealed substantial changes in the presented peptidome of NMD inhibited samples, and in vitro assays confirmed a remarkably high immunogenicity of NMD-regulated neoantigens as well as an enhanced HLA-I-dependent T cell-mediated tumor killing upon NMD inhibition. Tumor-targeted inhibition of NMD in immunocompetent (C57BL/6) and immunocompromised mouse models (NSG and RAG1-KO) confirmed increased T cell infiltration and a T cell-dependent control of tumor growth in vivo, accompanied by a greater clonotype diversity as determined by single-cell TCR sequencing, consistent with an expanded neoantigen repertoire. We thus demonstrate for the first time a critical dependency of TMBhigh tumors on enhanced NMD activity to manage mutation-derived byproducts and sustain tumor growth. NMD inhibition in SCLC led to an unbearable accumulation of mutant transcripts which, on the one hand, triggered ER stress and cell-intrinsic apoptosis, and on the other hand, translated into neoantigens that enhanced tumor immunogenicity. This dual TMB-dependent vulnerability to NMD inhibition offers an opportunity for developing novel tumor-targeted therapies in SCLC and potentially other TMBhigh tumors. Lucia A. Torres Fernández, Volker Boehm, Joel Kaufmann, Agnieszka Rumińska, Jonas P. Becker, Maria Garcia Marquez, Beaunelle de Bruijn, Christian Müller, Nazanin Alavinejad, Laura Lovric, Johanna Bihler, Kian R. Weihrauch, Laura Kaiser, Marcel Schmiel, Lukas Maas, Filippo Beleggia, Olta Ibruli, Bianca Göbel, Vignesh Sakthivelu, Graziella Bosco, Liu Fanyu, Ariadne Androulidaki, Silvia von Karstedt, Maria Cartolano, Johannes Brägelmann, Justinas Valiulis, Joshua D’Rozario, Nina Wobst, Katja Höpker, Felix John, Jürgen Wolf, Alexander Quaas, Stefan Knapp, Poorya Davoodi, Anna Schöllhorn, Cécile Gouttefangeas, Hans-Georg Rammensee, Angelika B. Riemer, Hans C. Reinhardt, Hans A. Schlößer, Niels H. Gehring, Martin Peifer, Roman K. Thomas, Julie George. Inhibition of nonsense-mediated decay in small cell lung cancer promotes tumor cell-intrinsic death and T cell cytotoxicity [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr A073.

Die intraoperative Pathologie ist ein zentrales Instrument während der chirurgischen Eingriffe, wo die präzise Resektionsrandbeurteilung und die Einschätzung der Dignität von Tumoren maßgeblich über den funktionellen Erhalt und die onkologische Sicherheit entscheiden. In der Otorhinolaryngologie kommt die Methode v. a. bei Plattenepithelkarzinomen („squamous cell carcinoma“, SCC) der Mundhöhle, des Pharynx und des Larynx zum Einsatz. Die diagnostische Präzision ist für SCC insgesamt hoch, variiert jedoch je nach Lokalisation und wird insbesondere durch Vorbehandlungen wie Radiotherapie oder neoadjuvante Chemotherapie eingeschränkt. Für Nicht-SCC-Entitäten, z. B. Speicheldrüsentumoren oder Lymphome, ist die Aussagekraft intraoperativer Diagnostik deutlich begrenzter. Neue Technologien wie stimulierte Raman-Histologie und schnelle Immunohistochemie könnten zukünftig die intraoperative Diagnostik im Kopf-Hals-Bereich beschleunigen und weiter präzisieren.

Germinal center markers are expressed in lymphoid follicles.

Esophageal adenocarcinoma (EAC) demonstrates poor survival rates despite multimodal treatments, with significant inter-patient variability in response to standard pre-/perioperative therapies. This study investigates the relationship between adherens junction (AJ) protein expression in pre-treatment biopsies and response to neoadjuvant therapies in EAC. Mass spectrometry-based proteomics was performed on diagnostic biopsies from 157 EAC patients who subsequently received either perioperative FLOT chemotherapy or neoadjuvant CROSS radiochemotherapy. Protein expression profiles were analyzed with emphasis on AJ components. Findings were correlated with treatment response and histopathological parameters. We identified a distinct protein cluster enriched for AJ components that significantly correlated with response to FLOT chemotherapy. Among FLOT major responders, 94% exhibited high AJ expression. Low AJ expression occurred across histological subtypes, with varying frequencies: 27% in tubular-intestinal, 40% in mixed-type, and 50% in diffuse carcinomas. Low AJ expression was significantly associated with a pro-inflammatory tumor microenvironment and extracellular matrix (ECM) remodeling. AJ protein expression represents a potential predictive parameter for FLOT chemotherapy response in EAC and defines distinct phenotypes. The association between reduced AJ expression and inflammatory features suggests these tumors may represent candidates for further investigation of targeted therapeutic approaches, though the role of immunotherapy in this context remains to be determined. Pre-treatment AJ assessment could guide therapy selection to avoid ineffective therapies.

Chronic constipation comprises heterogeneous clinical entities, including slow-transit constipation (STC) and functional defecation disorders such as obstructed defecation syndrome (ODS). Although neuroenteric mechanisms are implicated, reproducible histomorphological correlates remain incompletely defined, partly due to methodological heterogeneity and lack of standardized quantification. The study characterizes the myenteric plexus morphology and neuroimmune cell distribution across clinically defined subgroups of functional bowel disorders using a standardized digital pathology approach. Retrospective observational cohort study at a tertiary colorectal referral center. A total of 100 patients after bowel surgery were included: ODS (n = 17), STC (n = 24), combined ODS + STC (n = 28), and a control cohort without clinically evident bowel motility disorders (n = 31). Digital morphometric assessment of ganglionic density and morphology, neuronal content (immunohistochemistry against MAP2, HuC/D), and the distribution of CD3-positive T-lymphocytes within and around myenteric ganglia were performed. Ganglionic density differed significantly between groups (p = 0.002), with increased density in ODS, whereas STC values were comparable to controls. Neuronal content per ganglion was preserved across all groups as demonstrated by MAP2 and HuC/D analyses. In contrast, the presence of CD3-positive lymphocytes was reduced in all constipation groups, most pronounced in STC, affecting both the intra- and periganglionic compartments. Functional bowel motility and defecation disorders appear to show distinct neuroarchitectural and neuroimmune patterns. Increased ganglionic density in ODS contrasts with preserved neuronal content and reduced presence of T-lymphocytes, particularly in STC. These findings represent associations rather than proven disease mechanisms, derived from comparison with a surgical rather than a healthy control cohort. Standardized digital morphometry nonetheless provides a reproducible framework for phenotypic characterization of chronic constipation and may support future studies linking enteric structure to function. Clinicaltrials.gov (NCT05016700; 09/12/2020).

Schematic overview laser microdissection

Künstliche Intelligenz (KI) wird in der digitalen Pathologie zunehmend eingesetzt, um die Gewebeklassifizierung, Zelldetektion, Biomarkerquantifizierung, das Grading und die Vorhersage klinisch relevanter molekularer Veränderungen zu unterstützen. Aktuelle KI-Anwendungen in der Pathologie bei internistischen und onkologischen Erkrankungen werden zusammengefasst, mit Schwerpunkt auf den wichtigsten algorithmischen Ansätzen, repräsentativen diagnostischen Anwendungsfällen und derzeitigen Grenzen der klinischen Implementierung. Die vorliegende narrative Übersicht über jüngste Fortschritte beschreibt wesentliche Modelltypen, darunter Gewebesegmentierungssysteme, Algorithmen zur Erkennung einzelner Zellen, schwach überwachtes Lernen und Foundation-Modelle, Tools zur Auswertung der Immunhistochemie sowie multimodale oder Sprache-basierte basierte Anwendungen. Repräsentative Studien aus der Nieren‑, Leber‑, Lungen-, gastrointestinalen, hämatologischen und Schilddrüsenpathologie werden besprochen. In vielen Situationen verbessert KI die Reproduzierbarkeit, Objektivität und Effizienz. Einige Systeme erreichen eine Genauigkeit, die mit der von Experten vergleichbar ist. Die meisten KI-Tools befinden sich noch in der Validierungsphase, und nur wenige sind in die routinemäßige klinische Nutzung übergegangen. Künstliche Intelligenz könnte die diagnostische und prädiktive Histopathologie weiter optimieren. Ihre Rolle bleibt assistierend. Eine breitere Implementierung wird durch verschiedene Hürden und Engpässe begrenzt. Der zukünftige Fortschritt hängt von prospektiver Validierung und der Integration in routinemäßige digitale Arbeitsabläufe ab.

BackgroundSoft tissue sarcomas (STS) carry a high risk of relapse or metastasis even after complete resection. (Neo-)adjuvant chemotherapy benefits only a subset of patients, underscoring the need for predictive biomarkers. Schlafen 11 (SLFN11) has emerged as a marker of sensitivity to DNA-damaging agents. This study evaluated SLFN11 as a prognostic and predictive biomarker for (neo-)adjuvant chemotherapy in STS.Materials and methodsSLFN11 expression was assessed by immunohistochemistry in 242 patients with STS across different disease stages, using the H-score and percentage of positive tumor cells. Sub-cohorts included patients receiving neoadjuvant therapy (n = 33), primary resection (n = 193), palliative first-line chemotherapy (n = 26), or a palliative salvage therapy with trabectedin (n = 22). Associations between SLFN11 levels, clinicopathological features, and survival were analyzed.ResultsIn the neoadjuvant cohort, SLFN11 expression correlated with pathological tumor regression after chemotherapy alone (rho = 0.73, p = 0.016) and chemotherapy ± radiotherapy (rho = 0.62, p = 0.011). Among primarily resected STS treated with adjuvant chemotherapy ± radiotherapy, SLFN11-high tumors were associated with significantly longer overall survival (OS) (p = 0.007) and disease-free survival (DFS) (p = 0.022). SLFN11 was independently associated with improved outcome (OS: HR 0.06, p = 0.002; DFS: HR 0.08, p = 0.004). In the palliative first-line chemotherapy cohort, SLFN11-high tumors showed improved OS (p = 0.005) and progression-free survival (PFS) (p = 0.024), and SLFN11 remained independently predictive (OS: HR 0.11, p = 0.001). In the trabectedin cohort, SLFN11-high tumors demonstrated longer OS (p = 0.04) and PFS (p = 0.024).ConclusionSLFN11 is a prognostic and potentially predictive biomarker in STS in the context of chemotherapy. Our results support a prospective validation, standardization of SLFN11 assessment, and consecutive clinical implementation.

PDAC patients show activated or non-activated tumor draining lymph nodes.

MYC family members have been extensively studied as undruggable transcription factors regulating oncogenic signaling in highly aggressive tumors such as small cell lung cancer (SCLC), via promoter binding. Here, leveraging the previously described Myc-driven SCLC mouse model (RPM), we generated RPM-Miz1 ΔPOZ (RPMM) mice to uncover a Myc-dependent regulation of neuroendocrine (NE) differentiation, via enhancers. Our functional and genomic analyses reveal that Miz1 facilitates Myc binding to low-affinity E-boxes at distal chromosomal regions, thereby enabling Myc occupancy at sites with otherwise limited intrinsic affinity. We further show that SCLC patients and cellular models share an enrichment of low-affinity E-Box Myc binding motifs at enhancer regions that loop to genes of classic neuroendocrine differentiation. Integrated epigenetic and genomic analyses with AI-modeling implicate Myc/Miz1 binding at enhancers as the determinant for the expression of bona-fide neuroendocrine genes. In RPMM tumors, the suppression of neuroendocrine identity is paralleled by a redistribution of Myc protein towards promoter-proximal regions, hyper-activation of Myc transcriptional programs, apoptotic priming and enhanced sensitivity to etoposide. Together, these findings uncover Miz1/Myc-engaged enhancers as a central hub for neuroendocrine lineage programs and provide a mechanistic basis for a targeted inhibition of Miz1 to boost chemosensitivity in SCLC.

Maintaining DNA damage response (DDR) protein homeostasis is vital for genome integrity. This requires coordinated crosstalk between repair factors, such as RAD51 and MRE11, and the ubiquitin-proteasome system. Here, we identified a new node in the DDR network – ubiquilin-1 (UBQLN1), a member of the ubiquilin protein family that act as shuttles to transport ubiquitinated substrates to the proteasome. We observed that the loss of UBQLN1 exposes RAD51 to ubiquitination and degradation, thus functionally repressing homologous recombination (HR). Mechanistically, we showed that UBQLN1 exhibits a non-canonical function whereby it stabilizes RAD51 localized to the sites of DNA damage by preventing its ubiquitination. Intriguingly, overexpression of UBQLN1 repressed HR-mediated DSB repair by engaging ubiquitinated MRE11, shifting repair towards mutagenic single-strand annealing. We also noted frequent overexpression of UBQLN1 in human tumors, and its association with an aggressive phenotype. Using a Ubqln1 overexpression allele, we demonstrated an oncogenic role of Ubqln1 in lung adenocarcinoma resulting in increased tumor mutational burden, in vivo. Lastly, we showed that Ubqln1 overexpression causes lung adenocarcinomas to sensitize to PARP1 inhibition and immune-checkpoint blockade in vivo. We also identified human patients with a deleterious mutation in UBQLN1 that results in a phenotype consistent with the role of UBQLN1 in HR. Taken together, our study of UBQLN1 reveals that this ubiquilin constitutes an important node in the DDR network, in part by inducing ubiquitin-independent RAD51 stabilization. Furthermore, UBQLN1 overexpression can serve as a predictor of clinical sensitivity to PARP1 inhibition and immune-checkpoint blockade, which has important implications for cancer patient treatment.

T cells surround B-cell cluster in PDAC TLS.

TLS in PDAC patients are active germinal centers.

Gene expression TLS-high vs. TLS-low tumor tissue

Supplementary Figure S3: In support of Fig. 5: PD-L1 expression in the different therapy subgroups