A Multicentre Clinical Study of Sarcoma Personalised Treatment Using Patient-Derived Tumour Xenografts

AIMS

Medication for advanced sarcomas has not improved for three decades. Patient-derived tumour xenografts (PDTX) are a promising solution for developing new therapies and real-time personalised medicine because of their highly effective prediction of drug efficacy. However, there is a dearth of PDTX models for sarcomas due to the scarcity and heterogeneity of the disease.

MATERIALS AND METHODS

A multicentre clinical collaborative study (ChiCTR-OOC-17013617) was carried out. Fresh patient tumour tissues via resection or biopsy were used for the PDTX set-up. The standard medical care chosen by the physician was given to the patient, in parallel with testing on multiple regimens. The outcomes of patients' responses and PDTX tests were compared. Comprehensive analyses were carried out to assess the clinical value of PDTX for the treatment of sarcomas. Living tissues from successfully engrafted cases were deposited into a repository.

RESULTS

Forty-two cases, including 36 bone sarcomas and six soft-tissue sarcomas, were enrolled; the overall engraftment rate was 73.8%. Histopathological examination showed a 100% consistency between primary tumours and tumour grafts. The engraftment rate was independent of age, gender and sampling methods, but was associated with subtypes of tumour. The outgrowth time of tumour grafts could be associated with prognosis. Major somatic mutations in tumour grafts occurred primarily in common tumour driver genes. Poor prognosis was associated with the KMT2C mutation. A drug efficacy test showed complete concordance between the PDTX model and patients' responses in 17 regimens.

CONCLUSION

PDTX is an ideal preclinical model for sarcomas because of its faithful preservation of the heterogeneity of the disease, a satisfactory engraftment rate and high accuracy in its prediction of drug efficacy.

Establishment of a Patient-Derived Xenograft of Canine Enteropathy-Associated T-Cell Lymphoma, Large Cell Type

The pathogenesis of canine T-cell lymphoma remains incompletely understood, partly because there are no well-established in-vivo models to study these malignancies. For this study, we generated a patient-derived tumour xenograft (PDTX) from a 10-year-old neutered male golden retriever dog with enteropathy-associated intestinal T-cell lymphoma, large cell type. One of two female, 15-week-old beige/nude/XID mice developed a visible tumour 7 weeks after sections of tumour material from the spleen were surgically implanted. The histological appearance, immunophenotype and clonal antigen receptor rearrangements of the tumour from the recipient mouse showed that it was derived from the primary canine tumour. Our results indicate that immunodeficient mice are receptive hosts to develop in-vivo PDTX models to study the pathogenesis and management of canine T-cell lymphomas.

Preclinical models of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) is one of the most difficult human malignancies to treat. The 5-year survival rate of PDA patients is 7% and PDA is predicted to become the second leading cancer-related cause of death in the USA. Despite intensive efforts, the translation of findings in preclinical studies has been ineffective, due partially to the lack of preclinical models that faithfully recapitulate features of human PDA. Here, we review current preclinical models for human PDA (eg human PDA cell lines, cell line-based xenografts and patient-derived tumour xenografts). In addition, we discuss potential applications of the recently developed pancreatic ductal organoids, three-dimensional culture systems and organoid-based xenografts as new preclinical models for PDA.

Maintaining Tumor Heterogeneity in Patient-Derived Tumor Xenografts

Preclinical models often fail to capture the diverse heterogeneity of human malignancies and as such lack clinical predictive power. Patient-derived tumor xenografts (PDX) have emerged as a powerful technology: capable of retaining the molecular heterogeneity of their originating sample. However, heterogeneity within a tumor is governed by both cell-autonomous (e.g., genetic and epigenetic heterogeneity) and non-cell-autonomous (e.g., stromal heterogeneity) drivers. Although PDXs can largely recapitulate the polygenomic architecture of human tumors, they do not fully account for heterogeneity in the tumor microenvironment. Hence, these models have substantial utility in basic and translational research in cancer biology; however, study of stromal or immune drivers of malignant progression may be limited. Similarly, PDX models offer the ability to conduct patient-specific in vivo and ex vivo drug screens, but stromal contributions to treatment responses may be under-represented. This review discusses the sources and consequences of intratumor heterogeneity and how these are recapitulated in the PDX model. Limitations of the current generation of PDXs are discussed and strategies to improve several aspects of the model with respect to preserving heterogeneity are proposed.