Decoding drug resistance and apoptosis in biliary tract cancers using 3D tumor models

Background Biliary Tract Cancers (BTCs), including cholangiocarcinoma and gallbladder cancer, are aggressive malignancies characterized by late diagnosis, high mortality, and intrinsic resistance to standard chemotherapeutic regimens like gemcitabine and cisplatin. A critical barrier to improving therapeutic outcomes is the historical reliance on 2D monolayer cultures. These conventional models fail to recapitulate the complex Tumor Microenvironment (TME), leading to poor predictive validity and high attrition rates in drug discovery. Scope This review critically examines the paradigm shift from reductionist 2D cultures to advanced 3D tumor models—as superior in vitro platforms for decoding drug resistance and apoptosis evasion in BTCs, while acknowledging that 2D model limitations represent only one component of a broader translational pipeline that includes animal models, biomarker gaps, and anatomical challenges. Key Insights The article highlights that 3D architectures uniquely recapitulate physiological barriers absent in monolayers, including hypoxia-driven metabolic reprogramming, dense Extracellular Matrix (ECM) shielding, and drug distribution gradients. These models reveal specific “multicellular resistance” (MCR) mechanisms, such as the dysregulation of the Bcl-2 rheostat (particularly Bcl-xL and Mcl-1 dependence). Furthermore, 3D systems provide a more accurate context for investigating alternative cell death pathways, including ferroptosis and necroptosis, and for identifying quiescent cancer stem cell populations protected by the niche. Conclusion 3D tumor models, particularly PDOs, serve as high-fidelity “clinical avatars” that bridge the translational gap between preclinical screening and precision oncology. While challenges regarding standardization, immune component integration, and scalability remain, the adoption of these physiologically relevant systems is imperative for developing effective combinatorial therapies and overcoming the profound chemoresistance inherent to BTCs.