Patient-Derived Gastric Cancer Assembloids: Advancing Tumor Microenvironment Modeling

Study Background and Research Question

Gastric cancer remains a formidable clinical challenge, ranking as the fifth most diagnosed carcinoma and the second leading cause of cancer-related mortality globally. The five-year survival rate for patients with advanced or metastatic disease is less than 10%, despite multimodal treatments involving surgery, chemotherapy, targeted, and immune-based therapies. One persistent obstacle in improving outcomes is the pronounced heterogeneity of gastric tumors, which contributes to variable drug responses and limits the efficacy of current personalized treatment approaches. Conventional three-dimensional (3D) in vitro tumor models, such as patient-derived organoids, capture some aspects of tumor biology but often fail to recapitulate the complex cellular and microenvironmental niche—particularly the influence of diverse stromal components. Therefore, the central research question addressed by Shapira-Netanelov et al. (2025) is how to develop an in vitro model that more accurately reflects the cellular heterogeneity and microenvironment of patient-specific gastric tumors, and how such a model can improve the prediction of drug responses and mechanisms of resistance (reference study).

Key Innovation from the Reference Study

The study's principal innovation lies in the development of a patient-derived gastric cancer assembloid model that integrates matched epithelial tumor organoids with autologous stromal cell subpopulations, including mesenchymal stem cells, cancer-associated fibroblasts, and endothelial cells. Unlike traditional organoid culture, which typically consists of a single epithelial lineage, this assembloid approach reconstructs the tumor microenvironment by co-culturing distinct cell types derived from the same tumor sample. The inclusion of patient-matched stromal cells enables the model to recapitulate not only the cellular diversity but also the dynamic cell–cell interactions, extracellular matrix remodeling, and paracrine signaling that drive tumor progression and therapy resistance in vivo. By bridging the gap between reductionist organoid models and the complexity of human tumors, these assembloids provide a more physiologically relevant platform for studying gastric cancer biology and for preclinical drug evaluation.

Methods and Experimental Design Insights

The protocol established by Shapira-Netanelov et al. involves several key steps:

• Tissue Dissociation and Cell Expansion: Freshly resected gastric tumor tissue is enzymatically and mechanically dissociated to yield a heterogeneous cell suspension. Distinct cell populations are then expanded in cell-type specific media: organoid medium for epithelial cancer cells, mesenchymal stem cell medium, fibroblast medium, and endothelial cell medium.
• Co-Culture and Assembloid Formation: Tumor-derived epithelial and stromal subpopulations are recombined in an optimized assembloid medium that supports the growth and maintenance of each cell lineage. The ratios of epithelial to stromal cells can be tuned to model inter-patient variability.
• Characterization: Immunofluorescence staining is used to confirm the presence and spatial organization of epithelial and stromal markers. Transcriptomic profiling by RNA sequencing assesses global changes in gene expression, including signatures of inflammation, extracellular matrix remodeling, and tumor progression.
• Drug Response Assays: Cell viability and proliferation assays are performed following exposure to a panel of chemotherapeutic and targeted agents, enabling the assessment of drug sensitivity and resistance mechanisms in both organoid monocultures and assembloid co-cultures.

Protocol Parameters

• Tissue dissociation: Enzymatic digestion (e.g., collagenase/hyaluronidase) and mechanical trituration to single-cell suspension; optimize enzyme mix and incubation times to preserve cell viability.
• Cell expansion: Use lineage-specific media for initial outgrowth: organoid medium for tumor epithelium; specialized formulations for fibroblasts, mesenchymal stem cells, and endothelial cells.
• Assembloid co-culture: Combine epithelial and stromal cells at defined ratios (e.g., 1:1 or patient-specific ratios) in a matrix-supported 3D format; maintain in assembloid-supportive medium.
• Drug response assay: Apply candidate drugs at clinically relevant concentrations; monitor cell viability using ATP-based or imaging-based assays at 48–96 hours post-treatment.
• Gene expression analysis: Isolate RNA from assembloid and monoculture conditions for transcriptomic profiling to identify differentially expressed pathways.

Core Findings and Why They Matter

The optimized assembloid system closely mimics the cellular heterogeneity of primary gastric tumors, as demonstrated by the co-expression of epithelial and stromal markers and faithful recapitulation of spatial organization. Transcriptomic analysis revealed that assembloids, compared to monocultures, show higher expression of inflammatory cytokines, extracellular matrix remodeling genes, and tumor progression-associated markers. Notably, drug response assays uncovered significant variability in sensitivity to chemotherapeutic and targeted agents between monoculture organoids and assembloids. Some drugs retained efficacy across both models, while others lost activity in the assembloid context, implicating the stromal compartment as a critical modulator of drug resistance. These findings highlight the importance of tumor–stroma interactions in shaping therapeutic response and underscore the assembloid's value as a preclinical platform for personalized drug screening, mechanism-of-resistance studies, and biomarker discovery (reference study).

Comparison with Existing Internal Articles

The impact of stromal components on antifolate drug resistance and tumor microenvironment modeling is a recurring theme in the literature. Internal resources such as "Leucovorin Calcium: Strategic Methotrexate Rescue in Next-Gen Assembloids" and "Leucovorin Calcium: Precision Modulation of Tumor–Stroma" explore how calcium folinate enables detailed study of tumor–stroma interplay and antifolate resistance in complex assembloid systems. These articles provide technical insights into the integration of folate analogs for protection from methotrexate-induced growth suppression and for dissecting the folate metabolism pathway in advanced cancer models. The reference study extends these foundational insights by offering direct experimental evidence of how patient-matched stromal subpopulations alter drug sensitivity and gene expression profiles, thereby validating the need for physiologically relevant co-culture systems to advance translational oncology.

Limitations and Transferability

While the patient-derived gastric cancer assembloid model offers enhanced physiological relevance, several limitations must be acknowledged. The generation and maintenance of assembloids require access to fresh tumor tissue, specialized cell culture expertise, and tailored media formulations, which may limit scalability and reproducibility across different laboratories. The ratio and identity of stromal subpopulations are patient-specific and may not fully capture the diversity seen across broader patient cohorts. Furthermore, while the model allows for high-content drug screening and mechanistic studies, it does not recapitulate systemic factors such as immune cell infiltration or pharmacokinetics present in vivo. Nevertheless, the assembloid platform represents a significant advance compared to conventional organoid cultures and provides a robust foundation for preclinical research and personalized therapy development.

Research Support Resources

For researchers aiming to model protection from methotrexate-induced growth suppression, optimize cell proliferation assays, or interrogate the folate metabolism pathway in complex assembloid systems, high-purity reagents are essential. Leucovorin Calcium (SKU A2489) from APExBIO is widely used as a folate analog for methotrexate rescue, enabling accurate modeling of antifolate drug resistance and tumor–stroma interactions. Its defined solubility profile and stability at −20°C facilitate reliable experimental workflows. For detailed mechanistic guidance and protocol adaptation in assembloid cancer models, additional technical discussions are available in the linked internal resources above. Researchers should use Leucovorin Calcium strictly for scientific research purposes, in accordance with the product guidelines.