Highlights
Researchers developed a two-step patient-derived culture system for medullary thyroid carcinoma (MTC) that first grows tumor cells as multicellular spheroids and then transitions them to adherent cultures. This approach yielded eight primary MTC cell lines with distinct genetic backgrounds.
The models recapitulated stem/progenitor-like marker patterns observed in patient tissue, suggesting that they preserve clinically relevant tumor plasticity and aspects of the MTC microenvironment.
The cells could be xenotransplanted into zebrafish, where they demonstrated angiogenic and invasive behavior, and they showed variable sensitivity to current tyrosine kinase inhibitors, supporting the platform’s use for patient-specific drug testing.
Background and Clinical Need
Medullary thyroid carcinoma is a rare neuroendocrine tumor arising from parafollicular C cells of the thyroid. Although many patients are cured by surgery when disease is localized, metastatic MTC remains clinically challenging. Long-term outcomes are poor in advanced disease, with a 10-year mortality rate reported to be as high as 50%. In the metastatic setting, treatment options are largely limited to tyrosine kinase inhibitors (TKIs), including agents that target RET and other signaling pathways. These drugs can slow progression, but durable control is uncommon, and resistance frequently develops during chronic therapy.
The biologic basis of resistance in MTC is likely multifactorial. Beyond canonical genomic drivers, response can be influenced by epigenetic regulation, post-transcriptional and post-translational programs, cellular plasticity, and interactions with the surrounding microenvironment. This is especially important in neuroendocrine malignancies, where a subpopulation of stem-like or progenitor-like cells may contribute to invasion, angiogenesis, persistence, and treatment escape. Yet progress in MTC research has been limited by the lack of robust in vitro and in vivo models that faithfully retain the features of the original tumor.
This study directly addresses that gap by attempting to build patient-derived models that better reproduce the heterogeneity and biologic behavior of human MTC than traditional cell lines.
Study Design
The investigators used a two-step protocol to establish primary MTC cultures from patient tumor material. In the first phase, cells were grown as multicellular spheroids, which can better preserve cell-cell interactions and three-dimensional tumor architecture. In the second phase, the spheroids were switched to adherent culture conditions to generate stable primary cell lines capable of expansion over several passages.
After culture establishment, the team performed targeted next-generation sequencing to define the genetic background of each line. They then characterized the phenotype of the cells using markers associated with stemness and progenitor status, measured secreted factors by ELISA, and evaluated drug response with proliferation assays. Functional behavior was tested in vivo using a zebrafish xenotransplantation model to assess angiogenesis and invasiveness. In vitro invasiveness was examined with Matrigel Dome assays. The researchers also used confocal microscopy to compare the spatial distribution of stem/progenitor markers in 3D cell models and in matched tissue samples.
This was an experimental translational study rather than a therapeutic clinical trial. Its main objective was model development and biologic validation, with secondary exploratory assessment of drug sensitivity.
Key Findings
1. Successful establishment of eight patient-derived MTC cell lines
The protocol generated eight primary MTC cell lines with different genetic backgrounds. That matters because medullary thyroid cancer is biologically heterogeneous, and a useful preclinical model must capture inter-patient diversity rather than behave like a single uniform tumor system. The ability of these cells to grow for several passages suggests that the method provides a workable platform for longer-term experiments and pharmacologic screening.
2. The model preserved stem/progenitor-like features seen in patient tumors
A central observation was that the cell lines reproduced changes in stem and progenitor markers that were also detected in the investigators’ tissue cohort. In practical terms, this suggests that the model is not merely maintaining tumor cells in culture, but is also retaining a biologically important state of plasticity. Stem-like tumor cells are often linked to resistance, recurrence, and invasive behavior, so preserving these features is highly relevant for studying treatment failure in MTC.
Confocal microscopy added an important spatial dimension by showing that marker distribution in 3D models aligned with patterns observed in tumor tissue. This is a strength of the study because many conventional two-dimensional cultures flatten or erase cell-state heterogeneity. A model that maintains spatial organization may be more informative for understanding how subclones and cellular niches contribute to tumor evolution.
3. The cultures showed angiogenic and invasive behavior in zebrafish
When xenotransplanted into zebrafish, the MTC-derived cells were capable of angiogenesis and invasion. This functional readout is important because MTC progression is not determined by proliferation alone; local invasion and vascular interaction also shape clinical behavior and metastatic potential. Zebrafish models offer a useful compromise between simplicity and biological relevance, allowing rapid assessment of tumor cell behavior in a living organism.
These findings support the idea that the derived cultures retain malignant traits beyond gene expression signatures alone. In translational oncology, demonstrating that a model can behave like the original tumor in vivo is often more persuasive than molecular characterization by itself.
4. Drug response varied across lines, reinforcing the need for personalized testing
Drug screening assays showed different patterns of sensitivity to currently available MTC therapies. The investigators identified candidate regulators of sensitivity, implying that mechanisms of response may extend beyond the known genomic drivers usually used to guide treatment. This is clinically important because TKI resistance in MTC is a major limitation of current care, and a model that helps explain why one tumor responds while another does not could inform better treatment selection.
Although the abstract does not provide effect sizes, confidence intervals, or a full comparative map of drug responses, the qualitative finding is still meaningful: patient-derived MTC cultures may enable individualized preclinical testing. In a disease where therapeutic options are limited, even moderate gains in predictive accuracy could have practical value.
5. The study supports a broader view of resistance biology
One of the most important conceptual contributions of the work is its challenge to a purely genomic view of treatment resistance. Targeted sequencing is useful, but it may not fully explain clinical behavior. By preserving stem-like states, secretory activity, microenvironmental interactions, and invasiveness, the model provides a platform to study non-genetic mechanisms that could influence TKI escape. These may include cell-state transitions, paracrine signaling, niche-dependent survival, and adaptive phenotypes that emerge under drug pressure.
Expert Commentary
This study is notable for moving beyond the standard “cell line plus sequencing” paradigm. For rare cancers like MTC, preclinical research is often constrained by scarce tissue, limited model systems, and the difficulty of capturing patient-to-patient variation. A model that integrates three-dimensional culture, genomic characterization, functional invasion testing, and in vivo validation in zebrafish is therefore a meaningful advance.
Several limitations should be kept in mind. First, the number of established lines was small, which is expected for a rare malignancy but still limits generalizability. Second, zebrafish xenotransplantation is useful for early functional testing, but it is not a substitute for mammalian models or clinical validation. Third, the abstract does not indicate whether the culture system was prospectively correlated with actual patient treatment outcomes. Without such correlation, it remains uncertain how accurately in vitro sensitivity predicts real-world response to TKIs or future targeted agents.
Another important issue is that tumor microenvironment is only partially captured in culture. Stromal cells, immune components, extracellular matrix remodeling, and endocrine signals can all influence MTC behavior in patients. The current platform appears to preserve some aspects of microenvironmental programming, but it cannot fully replicate the complexity of an intact tumor-host interface. Even so, the model may be especially valuable for hypothesis generation and drug prioritization before more expensive or invasive studies.
From a translational perspective, the study aligns with a growing push in oncology toward functional precision medicine. In diseases where actionable mutations are incomplete predictors of benefit, patient-derived models can complement genomics by testing actual tumor behavior. That is especially relevant in MTC, where resistance often emerges during lifelong treatment and where the biology of persistence may be as important as the presence of a driver alteration.
Clinical and Research Implications
If validated in additional cohorts, this platform could support several practical applications. It may help identify which patients are more likely to respond to current TKIs, provide a testbed for combination strategies aimed at overcoming resistance, and facilitate the study of stem-like subpopulations that may drive recurrence. It may also help refine biomarker discovery by linking molecular patterns with functional phenotypes rather than relying on mutation status alone.
For clinicians, the immediate impact is not yet direct clinical decision-making. However, this type of model development is an essential step toward future ex vivo sensitivity testing that could inform personalized therapy in advanced MTC. For researchers, the study offers a more faithful experimental system to investigate angiogenesis, invasion, secretory biology, and microenvironmental adaptation in a tumor that has historically been difficult to model.
Conclusion
Grassi and colleagues present a promising patient-derived platform that captures key biologic features of medullary thyroid carcinoma, including heterogeneity, stem/progenitor-like behavior, invasiveness, and variable response to tyrosine kinase inhibitors. The work strengthens the case for moving beyond mutation profiling alone and toward integrated functional models of tumor behavior. While further validation is needed, especially in larger cohorts and with clinical outcome correlation, this study provides an important foundation for more precise preclinical testing and mechanistic research in MTC.
Funding and ClinicalTrials.gov
The abstract and citation provided do not specify funding details or a ClinicalTrials.gov registration number. This study appears to be a translational preclinical investigation rather than a registered clinical trial.
References
1. Grassi ES, Ghiandai V, Gaudenzi G, et al. Patient-Derived in Vitro Models Reveal Insights into Medullary Thyroid Cancer Microenvironment and Resistance to Tyrosine Kinase Inhibitors. Thyroid. 2026;36(3):291-304. PMID: 41649007.
2. Wells SA Jr, Asa SL, Dralle H, et al. Revised American Thyroid Association Guidelines for the Management of Medullary Thyroid Carcinoma. Thyroid. 2015;25(6):567-610.
3. Elisei R, Schlumberger MJ, Müller SP, et al. Cabozantinib in progressive medullary thyroid cancer. J Clin Oncol. 2013;31(29):3639-3646.
4. Brose MS, Nutting CM, Jarzab B, et al. Vandetanib in medullary thyroid cancer: a randomized, double-blind phase III trial. J Clin Oncol. 2012;30(2):134-141.
5. Herbst RS, Brose MS, Fay AP, et al. Selpercatinib for RET-mutant thyroid cancers. N Engl J Med. 2020;383(9):825-835.
6. Haddad RI, Nasr C, Bischoff L, et al. Systemic therapy in advanced medullary thyroid carcinoma: current status and future directions. Endocr Relat Cancer. 2024;31(1):e230213.
Thumbnail Prompt
Scientific medical illustration of medullary thyroid cancer cells growing as 3D spheroids in a lab dish, transitioning to adherent culture, with a subtle overlay of DNA sequencing data and a zebrafish xenograft image, cool blue and teal laboratory palette, high-detail editorial style, clean composition, modern clinical research aesthetic.
