The Chick Embryo Xenograft Model for Malignant Pleural Mesothelioma: A Cost and Time Efficient 3Rs Model for Drug Target Evaluation

SIMPLE SUMMARY: Malignant pleural mesothelioma is a cancer of the lung lining, normally caused by asbestos, that develops decades after exposure. Chemotherapy, and recently more targeted drugs, show some benefit although only a minority of patients respond and invariably the cancer eventually escapes control. Several key genetic changes in mesothelioma differ from patient to patient, which may influence how their cancer responds to treatments. We have developed a new preclinical model using fertilised hen’s eggs as an alternative to laboratory rodents. Mesothelioma cells are labelled to allow monitoring of tumour growth and/or regression using fluorescence and longitudinal bioluminescence imaging in addition to histology. All cell lines tested efficiently form tumour nodules within seven days, supported by a blood supply and stromal chick cells. The model is rapid, cost effective, scalable, and adaptable with multiple potential endpoints, to enable evaluation of drug targets against the range of common mesothelioma genetic backgrounds. ABSTRACT: Malignant pleural mesothelioma (MPM) has limited treatment options and poor prognosis. Frequent inactivation of the tumour suppressors BAP1, NF2 and P16 may differentially sensitise tumours to treatments. We have established chick chorioallantoic membrane (CAM) xenograft models of low-passage MPM cell lines and protocols for evaluating drug responses. Ten cell lines, representing the spectrum of histological subtypes and tumour suppressor status, were dual labelled for fluorescence/bioluminescence imaging and implanted on the CAM at E7. Bioluminescence was used to assess viability of primary tumours, which were excised at E14 for immunohistological staining or real-time PCR. All MPM cell lines engrafted efficiently forming vascularised nodules, however their size, morphology and interaction with chick cells varied. MPM phenotypes including local invasion, fibroblast recruitment, tumour angiogenesis and vascular remodelling were evident. Bioluminescence imaging could be used to reliably estimate tumour burden pre- and post-treatment, correlating with tumour weight and Ki-67 staining. In conclusion, MPM-CAM models recapitulate important features of the disease and are suitable to assess drug targets using a broad range of MPM cell lines that allow histological or genetic stratification. They are amenable to multi-modal imaging, potentially offering a time and cost-efficient, 3Rs-compliant alternative to rodent xenograft models to prioritise candidate compounds from in vitro studies.