Establishment and characterization of a primary human chordoma xenograft model

Abstract

Object: Chordomas are rare tumors arising from remnants of the notochord. Because of the challenges in achieving a complete resection, the radioresistant nature of these tumors, and the lack of effective chemotherapeutics, the median survival for patients with chordomas is approximately 6 years. Reproducible preclinical model systems that closely mimic the original patient's tumor are essential for the development and evaluation of effective therapeutics. Currently, there are only a few established chordoma cell lines and no primary xenograft model. In this study, the authors aimed to develop a primary chordoma xenograft model.

Methods: The authors implanted independent tumor samples from 2 patients into athymic nude mice. The resulting xenograft line was characterized by histopathological analysis and immunohistochemical staining. The patient's tumor and serial passages of the xenograft were genomically analyzed using a 660,000 single-nucleotide polymorphism array.

Results: A serially transplantable xenograft was established from one of the 2 patient samples. Histopathological analysis and immunohistochemical staining for S100 protein, epithelial membrane antigen, and cytokeratin AE1/AE3 of the primary patient sample and the xenografts confirmed that the xenografts were identical to the original chordoma obtained from the patient. Immunohistochemical staining and western blot analysis confirmed the presence of brachyury, a recently described marker of chordomas, in the tumor from the patient and each of the xenografts. Genome-wide variation was assessed between the patient's tumor and the xenografts and was found to be more than 99.9% concordant.

Conclusions: To the best of their knowledge, the authors have established the first primary chordoma xenograft that will provide a useful preclinical model for this disease and a platform for therapeutic development.

Fig. 1

Preoperative MR images. Preoperative sagittal T1-weighted image obtained after administration of Gd (A) and axial T2-weighted image (B) demonstrating a large clival chordoma with significant intracranial extension and mass effect on the optic apparatus and the brainstem.

Fig. 2

Photographs of the primary chordoma xenograft. A: Photograph of a nude mouse with bilateral chordoma xenograft tumors. B: Gross appearance of the bilateral xenograft tumors harvested from the animal shown in panel A demonstrating a lobulated appearance.

Fig. 3

Histochemical and immunohistochemical evaluation of chordoma xenografts. Paraffin-embedded and formalin-fixed sections from the patient’s primary tumor and chordoma xenografts were stained with H & E (A–D), and immunoperoxidase stains specific for cytokeratin (AE1/AE3) (E–H) and S100 protein (I–L). Original magnification × 100.

Fig. 4

Brachyury expression. Expression of brachyury in the patient tumor (P0), xenograft passage 1, mouse A (P1-A), xenograft passage 1, mouse B (P1-B), and xenograft passage 2 (P2) was determined by immunohistochemical (A) and western blot (B) analyses. A negative control of normal brain (B) was also run in the western blot analysis. Original magnification × 160.

Fig. 5

Short-term cell line cultures. A: Cells with the typical physaliphorous features characteristic of chordoma. B: Non-vacuolated cells present in the chordoma cultures. C: Growth curves of JHH-2009–011 cultures. D: Western blot analysis for brachyury expression: patient tumor (P0), U87MG glioma cell line, and JHH-2009–011 culture.