The nuclear deubiquitylase BRCA1-associated protein 1 (BAP1) is frequently inactivated in malignant pleural mesothelioma (MPM) and germline BAP1 mutation predisposes to cancers including MPM. To explore the influence on cell physiology and drug sensitivity, we sequentially edited a predisposition mutation (w-) and a promoter trap (KO) into human mesothelial cells. BAP1w-/KO MeT5A cells express less BAP1 protein and phenocopy key aspects of BAP1 loss in MPM. Stable isotope labeling with amino acids in cell culture–mass spectrometry revealed evidence of metabolic adaptation, with concomitant alteration of cellular metabolites. In MeT5A, BAP1 deficiency reduces glycolytic enzyme levels but increases enzymes involved in the tricarboxylic acid cycle and anaplerotic pathways. Notably both argininosuccinate synthase 1 (ASS1), essential for cellular synthesis of arginine, and its substrate aspartate, are elevated in BAP1w-/KO MeT5A cells. Likewise, ASS1 expression is higher in BAP1-altered MPM cell lines, and inversely correlates with BAP1 in The Cancer Genome Atlas MESO dataset. Elevated ASS1 is also evident by IHC staining in epithelioid MPM lacking nuclear BAP1 expression, with improved survival among patients with BAP1-negative/ASS1-expressing tumors. Alterations in arginine metabolism may sensitize cells to metabolic drugs and we find that BAP1-negative/ASS1-expressing MPM cell lines are more sensitive to ASS1 inhibition, although not to inhibition of purine synthesis by mizoribine. Importantly, BAP1w-/KO MeT5A become desensitized to arginine deprivation by pegylated arginine deiminase (ADI-PEG20), phenocopying BAP1-negative/ASS1-expressing MPM cell lines. Implications: Our data reveal an interrelationship between BAP1 and arginine metabolism, providing a potential means of identifying patients with epithelioid MPM likely to benefit from ADI-PEG20.

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.

Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with asbestos exposure. MPM is often diagnosed late, at a point where limited treatment options are available, but early intervention could improve the chances of successful treatment for MPM patients. Biomarkers to detect MPM in at-risk individuals are needed to implement early diagnosis technologies. Volatile organic compounds (VOCs) have previously shown diagnostic potential as biomarkers when analysed in MPM patient breath. In this study, chorioallantoic membrane (CAM) xenografts of MPM cell lines were used as models of MPM tumour development for VOC biomarker discovery with the aim of generating targets for investigation in breath, biopsies or other complex matrices. VOC headspace analysis of biphasic or epithelioid MPM CAM xenografts was performed using solid-phase microextraction and gas chromatography-mass spectrometry. We successfully demonstrated the capture, analysis and separation of VOC signatures from CAM xenografts and controls. A panel of VOCs was identified that showed discrimination between MPM xenografts generated from biphasic and epithelioid cells and CAM controls. This is the first application of the CAM xenograft model for the discovery of VOC biomarkers associated with MPM histological subtypes. These findings support the potential utility of non-invasive VOC profiling from breath or headspace analysis of tissues for detection and monitoring of MPM.

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 therapies using a broad range of MPM cell lines that allow histological or genetic stratification. They are amenable to multi-modal imaging, offering a time and cost-efficient, 3Rs-compliant alternative to rodent xenograft models to prioritise candidate compounds from in vitro studies.

Background Pleural mesothelioma is a cancer of the lung lining associated with asbestos exposure. Platinum/pemetrexed chemotherapy has been used for many years but provides little benefit and, despite recent immunotherapy advances, prognosis remains poor underpinning the need for development of novel therapeutics or drug repurposing. Fertilized hens’ eggs provide a rapid and cost-effective alternative to murine models of pleural mesothelioma which are commonly used in preclinical studies, with chorioallantoic membrane (CAM) xenografts being a partial replacement for mouse flank xenografts. Here we describe methods to generate mesothelioma patient-derived xenografts on the CAM (CAM-PDX), and to subsequently assess these PDX nodules by preclinical imaging and histology. Methods Fragments of surplus mesothelioma tissue obtained from patient biopsies were implanted onto the CAM on embryonic day 7 (E7), fresh or following cryopreservation, with the established PDX dissected on E14 and fixed for histological/immunohistochemical analysis. The optimal freezing method was determined by comparing tissue integrity and cellular content of cryopreserved tissue fragments with paired fresh samples via histological/immunohistochemical analyses. [ 18 F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) was used to assess viability of PDXs in ovo. Results Methodologies for processing, cryopreservation, re-animation, and engraftment of mesothelioma tissue fragments were established. Cryopreservation of biopsy samples and parallel processing of contiguous sections allows for assessment of mesothelioma cellularity. CAM-PDXs, generated from fresh or slow-frozen tissue, were well vascularized whilst maintaining the architecture and cellular composition of the patient tissue. Furthermore, uptake of [ 18 F]-FDG following intravenous injection could be visualized and quantified. Conclusions The CAM is a rapid platform for engrafting patient-derived tissue, maintaining elements of the tumor microenvironment and recapitulating heterogeneity observed in mesothelioma. Combining the CAM-PDX model and FDG-PET/CT provides a quantitative in vivo platform for pre-screening of novel treatment strategies and drug combinations, with the potential for development of patient tumor avatars for predicting clinical response.

Background Pleural mesothelioma is a cancer of the lung lining associated with asbestos exposure. Platinum/pemetrexed chemotherapy has been used for many years but provides little benefit and, despite recent immunotherapy advances, prognosis remains poor underpinning the need for development of novel therapeutics or drug repurposing. Fertilized hens’ eggs provide a rapid and cost-effective alternative to murine models of pleural mesothelioma which are commonly used in preclinical studies, with chorioallantoic membrane (CAM) xenografts being a partial replacement for mouse flank xenografts. Here we describe methods to generate mesothelioma patient-derived xenografts on the CAM (CAM-PDX), and to subsequently assess these PDX nodules by preclinical imaging and histology. Methods Fragments of surplus mesothelioma tissue obtained from patient biopsies were implanted onto the CAM on embryonic day 7 (E7), fresh or following cryopreservation, with the established PDX dissected on E14 and fixed for histological/immunohistochemical analysis. The optimal freezing method was determined by comparing tissue integrity and cellular content of cryopreserved tissue fragments with paired fresh samples via histological/immunohistochemical analyses. [18F]-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) was used to assess viability of PDXs in ovo. Results Methodologies for processing, cryopreservation, re-animation, and engraftment of mesothelioma tissue fragments were established. Cryopreservation of biopsy samples and parallel processing of contiguous sections allows for assessment of mesothelioma cellularity. CAM-PDXs, generated from fresh or slow-frozen tissue, were well vascularized whilst maintaining the architecture and cellular composition of the patient tissue. Furthermore, uptake of [18F]-FDG following intravenous injection could be visualized and quantified. Conclusions The CAM is a rapid platform for engrafting patient-derived tissue, maintaining elements of the tumor microenvironment and recapitulating heterogeneity observed in mesothelioma. Combining the CAM-PDX model and FDG-PET/CT provides a quantitative in vivo platform for pre-screening of novel treatment strategies and drug combinations, with the potential for development of patient tumor avatars for predicting clinical response.