Abstract
Ewing sarcoma and osteosarcoma represent the two most common primary bone tumours in childhood and adolescence, with bone metastases being the most adverse prognostic factor. In prostate cancer, osseous metastasis poses a major clinical challenge. We developed a preclinical orthotopic model of Ewing sarcoma, reflecting the biology of the tumour-bone interactions in human disease and allowing in vivo monitoring of disease progression, and compared this with models of osteosarcoma and prostate carcinoma. Human tumour cell lines were transplanted into non-obese diabetic/severe combined immunodeficient (NSG) and Rag2−/−/γc−/− mice by intrafemoral injection. For Ewing sarcoma, minimal cell numbers (1000–5000) injected in small volumes were able to induce orthotopic tumour growth. Tumour progression was studied using positron emission tomography, computed tomography, magnetic resonance imaging and bioluminescent imaging. Tumours and their interactions with bones were examined by histology. Each tumour induced bone destruction and outgrowth of extramedullary tumour masses, together with characteristic changes in bone that were well visualised by computed tomography, which correlated with post-mortem histology. Ewing sarcoma and, to a lesser extent, osteosarcoma cells induced prominent reactive new bone formation. Osteosarcoma cells produced osteoid and mineralised “malignant” bone within the tumour mass itself. Injection of prostate carcinoma cells led to osteoclast-driven osteolytic lesions. Bioluminescent imaging of Ewing sarcoma xenografts allowed easy and rapid monitoring of tumour growth and detection of tumour dissemination to lungs, liver and bone. Magnetic resonance imaging proved useful for monitoring soft tissue tumour growth and volume. Positron emission tomography proved to be of limited use in this model. Overall, we have developed an orthotopic in vivo model for Ewing sarcoma and other primary and secondary human bone malignancies, which resemble the human disease. We have shown the utility of small animal bioimaging for tracking disease progression, making this model a useful assay for preclinical drug testing.
Highlights
The complex three dimensional anatomy of bone undergoes constant remodelling dependent upon the coordinated activities of multiple resident cell types
In this study we have developed preclinical orthotopic models of Ewing sarcoma and other primary and metastatic bone tumours by injecting cells directly into the femur of young NSG or Rag22/ 2 cc2/2 mice
For Ewing sarcoma, our model is the first to combine an intraosseous orthotopic approach with evaluation of different imaging approaches to monitor tumour growth and dissemination, including disease tracking by bioluminescent imaging
Summary
The complex three dimensional anatomy of bone undergoes constant remodelling dependent upon the coordinated activities of multiple resident cell types. The growth of primary or metastatic cancer cells within the bone disturbs this equilibrium, producing clinically important changes in bone structure including aberrant new bone formation and bone destruction [1] These changes may have significant clinical consequences such as severe bone pain, nerve compression syndromes, hypercalcaemia, cytopenias and pathological fractures, which may reduce quality of life but in many cases correlate with reduced survival [2,3,4]. Osteosarcomas are often localized to the metaphyseal region of long bones, with the region around the knee involved in around 60% of cases [5] For both tumours, metastatic osseous spread is a feature of poor prognosis disease. More than two thirds of patients with advanced prostate carcinoma develop bone metastases conferring a poor prognosis, with the axial skeleton most frequently affected [9]
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