Abstract
Despite recent medical advances, colorectal cancer (CRC) remains the second-leading cause of cancer-related death worldwide. For patients with KRAS wild-type metastatic CRC, the monoclonal antibody cetuximab, which targets the epidermal growth factor receptor (EGFR), is an approved treatment option. However, therapeutic success is often limited by the emergence of drug-resistant cancer cell populations within a few months. Therefore, alternative strategies to effectively target cetuximab-refractory CRC are urgently needed. Here, we sought to identify second-line therapeutic strategies using a CRC cell line with acquired cetuximab resistance as a model. Transcriptomic profiling of the resistant cells identified the apoptosis pathway as a potential therapeutic target, which was supported by their increased susceptibility to BH3-mimetics targeting the anti-apoptotic proteins MCL-1 and BCL-xL under both 2D and 3D culture conditions. These findings were validated in organotypic CRC slice cultures generated from cetuximab-resistant patient-derived xenografts (PDXs). Multiplex immunofluorescence staining demonstrated that BCL-xL inhibition effectively triggered apoptosis in heterogeneous PDX tumor slice models, including models harboring oncogenic BRAF mutations. Our findings suggest that cetuximab-resistant CRC retains apoptotic competence, and that BCL-xL inhibition serves as a robust alternative therapeutic strategy that is largely independent of the tumor mutational profile.
Data availability
The RNA-sequencing data for LIM1215-parental and -R1/R2 cells are available on the GEO website under accession number GSE299943. The RNA-sequencing data for the PDX models are available from Charles River Laboratories (Freiburg, Germany) upon request. Furthermore, uncropped western blots performed in this study are included in this publication. All data and materials reported in this publication will be shared by the lead contact upon request.
Code availability
The codes for the RNA sequencing analysis will be shared by the lead contact upon request.
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Acknowledgements
This work was supported by the Ministry of Science, Research and Arts Baden-Württemberg within the 3R-US project (33-7533-6-1522/2/3). MB is supported by the Deutsche Forschungsgemeinschaft (DFG) – CRC1479 (Project ID 441891347-S1), CRC 1160 (Project ID 256073931-Z02), CRC1453 (Project ID 431984000-S1), TRR167 (Project ID 259373024-Z01), TRR 359 (Project ID 491676693-Z01), TRR 353 (Project ID 471011418-SP02) and FOR 5476 UcarE (Project ID 493802833-P7) and by the German Federal Ministry of Education and Research (BMBF) within the National Decade against Cancer program PM4Onco–FKZ 01ZZ2322A (to MB and PM) and SATURN3 (01KD2206L to MB). Figures 1A and 6A were created with BioRender.com. The funders had no role in study design, data collection and analysis, publication decision, or manuscript preparation. We thank Dr. Oliver Seifert, Alexandra Kraske and Laura Böckmann (University of Stuttgart), as well as Kerstin Willecke (Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology) for their excellent technical support. We thank Kai Hirzel (University of Stuttgart) for 3D-printing the customized molds for tumor embedding, as well as Dr. Zeynab Najafova and Akshay Kanakan (Robert Bosch Center for Tumor Diseases) for providing PANC-1 and AsPC-1 cell lines.
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SA designed and performed the experiments, analyzed the data and prepared the figures. RS and LMW assisted with the cellular assays. MD and JT provided their expertise with slice cultures and multiplex immunofluorescence staining. JS and EO provided the PDX model data and tissues. TLE and SA performed RNA-seq on the LIM1215 cells. TLE, ACB and PM analyzed the RNA-seq data from cells and tissues. MAO designed the study, acquired the funding, and supervised the work with conceptual support from REK, RT, SAJ, MB and FE. SA and MAO wrote the manuscript. RT was involved in preparing the final manuscript. All authors reviewed the manuscript and provided feedback.
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All animal procedures were performed in an AAALAC-accredited facility and were in accordance with the Guide for the Care and Use of Laboratory Animals of the Society of Laboratory Animals (GV SOLAS). Animal experiments were approved by the Committee on the Ethics of Animal Experiments of the regional council (Regierungspräsidium Freiburg, Abt. Landwirtschaft, Ländlicher Raum, Veterinär- und Lebensmittelwesen permit-#: I-19/02 und G-23/086).
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Asmanidou, S., Thiel, J., Ekstrom, T.L. et al. BCL-xL as a therapeutic target in cetuximab-refractory colorectal cancer. Cell Death Dis (2026). https://doi.org/10.1038/s41419-026-08434-5
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DOI: https://doi.org/10.1038/s41419-026-08434-5
