The PDX model is an animal model in which human tumor tissue is transplanted into immunodeficient mice and grows in the environment provided by the mice1. Traditional tumor cell line models suffer from several disadvantages, such as the lack of heterogeneity, the inability to retain the tumor microenvironment, the vulnerability to genetic variations during repeated in vitro passages, and the poor clinical application2,3. The main drawbacks of genetically engineered animal models are the potential loss of the genomic features of human tumors, the introduction of new unknown mutations, and the difficulty in identifying the degree of homology between mouse tumors and human tumors4. In addition, the preparation of genetically engineered animal models is expensive, time-consuming, and relatively inefficient4.
The PDX model has many advantages over other tumor models in terms of reflecting tumor heterogeneity. From the perspective of histopathology, although the mouse counterpart replaces the human stroma over time, the PDX model preserves the morphological structure of the primary tumor well. In addition, the PDX model conserves the metabolomic identity of the primary tumor for at least four generations and better reflects the complex inter-relationships between tumor cells and their microenvironment, making it unique in simulating the growth, metastasis, angiogenesis, and immunosuppression of human tumor tissue5,6,7. At the cellular and molecular levels, the PDX model accurately reflects the inter- and intra-tumor heterogeneity of human tumors, as well as the phenotypic and molecular characteristics of original cancer, including gene expression patterns, mutation status, copy number, and DNA methylation and proteomics8,9. PDX models with different passages have the same sensitivity to drug therapy, indicating that the gene expression of PDX models is highly stable10,11. Studies have shown an excellent correlation between the response of the PDX model to a drug and the clinical responses of patients to that drug12,13. Therefore, the PDX model has emerged as a powerful preclinical and translational research model, particularly for drug screening and clinical prognosis prediction.
Thyroid cancer is a common malignant tumor of the endocrine system and is a human malignancy that has shown a rapid increase in incidence in recent years14. Anaplastic thyroid carcinoma (ATC) is the most malignant thyroid cancer, with a median patient survival of only 4.8 months15. Although only a minority of thyroid cancer patients are diagnosed with ATC each year in China, the mortality rate is close to 100%16,17,18. ATC usually grows rapidly and invades the adjacent tissues of the neck as well as the cervical lymph nodes, and about half of the patients have distant metastases19,20. Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer in the world and one of the leading causes of cancer deaths, with an estimated 600,000 people suffering from HNSCC each year21,22,23. HNSCC includes a large number of tumors, including those in the nose, sinuses, mouth, tonsils, pharynx, and larynx24. ATC and HNSCC are two of the main head and neck malignancies. In order to facilitate the development of novel therapeutic agents and personalized treatments, it is necessary to develop robust and advanced preclinical animal models such as PDX models of ATC and HNSCC.
This article introduces detailed methods for establishing the subcutaneous PDX model of ATC and HNSCC, analyzes the key factors affecting the tumor take rate in model construction, and compares the histopathological characteristics between the PDX model and the primary tumor. Meanwhile, in this work, in vivo pharmacodynamic tests were performed using the successfully constructed PDX models in order to validate their clinical relevance.