Impact of limb amputation and cisplatin chemotherapy on metastatic progression in mouse models of osteosarcoma

OBSERVE: guidelines for the refinement of rodent cancer models

Existing guidelines on the preparation (Planning Research and Experimental Procedures on Animals: Recommendations for Excellence (PREPARE)) and reporting (Animal Research: Reporting of In Vivo Experiments (ARRIVE)) of animal experiments do not provide a clear and standardized approach for refinement during in vivo cancer studies, resulting in the publication of generic methodological sections that poorly reflect the attempts made at accurately monitoring different pathologies. Compliance with the 3Rs guidelines has mainly focused on reduction and replacement; however, refinement has been harder to implement. The Oncology Best-practices: Signs, Endpoints and Refinements for in Vivo Experiments (OBSERVE) guidelines are the result of a European initiative supported by EurOPDX and INFRAFRONTIER, and aim to facilitate the refinement of studies using in vivo cancer models by offering robust and practical recommendations on approaches to research scientists and animal care staff. We listed cancer-specific clinical signs as a reference point and from there developed sets of guidelines for a wide variety of rodent models, including genetically engineered models and patient derived xenografts. In this Consensus Statement, we systematically and comprehensively address refinement and monitoring approaches during the design and execution of murine cancer studies. We elaborate on the appropriate preparation of tumor-initiating biologicals and the refinement of tumor-implantation methods. We describe the clinical signs to monitor associated with tumor growth, the appropriate follow-up of animals tailored to varying clinical signs and humane endpoints, and an overview of severity assessment in relation to clinical signs, implantation method and tumor characteristics. The guidelines provide oncology researchers clear and robust guidance for the refinement of in vivo cancer models.

Magnetic resonance imaging-guided intracranial resection of glioblastoma tumors in patient-derived orthotopic xenografts leads to clinically relevant tumor recurrence

BACKGROUND

Preclinical in vivo cancer models are essential tools for investigating tumor progression and response to treatment prior to clinical trials. Although treatment modalities are regularly assessed in mice upon tumor growth in vivo, surgical resection remains challenging, particularly in the orthotopic site. Here, we report a successful surgical resection of glioblastoma (GBM) in patient-derived orthotopic xenografts (PDOXs).

METHODS

We derived a cohort of 46 GBM PDOX models that faithfully recapitulate human disease in mice. We assessed the detection and quantification of intracranial tumors using magnetic resonance imaging (MRI).To evaluate feasibility of surgical resection in PDOXs, we selected two models representing histopathological features of GBM tumors, including diffuse growth into the mouse brain. Surgical resection in the mouse brains was performed based on MRI-guided coordinates. Survival study followed by MRI and immunohistochemistry-based evaluation of recurrent tumors allowed for assessment of clinically relevant parameters.

RESULTS

We demonstrate the utility of MRI for the noninvasive assessment of in vivo tumor growth, preoperative programming of resection coordinates and follow-up of tumor recurrence. We report tumor detection by MRI in 90% of GBM PDOX models (36/40), of which 55% (22/40) can be reliably quantified during tumor growth. We show that a surgical resection protocol in mice carrying diffuse primary GBM tumors in the brain leads to clinically relevant outcomes. Similar to neurosurgery in patients, we achieved a near total to complete extent of tumor resection, and mice with resected tumors presented significantly increased survival. The remaining unresected GBM cells that invaded the normal mouse brain prior to surgery regrew tumors with similar histopathological features and tumor microenvironments to the primary tumors.

CONCLUSIONS

Our data positions GBM PDOXs developed in mouse brains as a valuable preclinical model for conducting therapeutic studies that involve surgical tumor resection. The high detectability of tumors by MRI across a substantial number of PDOX models in mice will allow for scalability of our approach toward specific tumor types for efficacy studies in precision medicine-oriented approaches. Additionally, these models hold promise for the development of enhanced image-guided surgery protocols.

Patterns of metastatic progression and association with clinical outcomes in canine osteosarcoma: A necropsy study of 83 dogs

Osteosarcoma is a highly metastatic primary bone tumour that occurs spontaneously in both pet dogs and humans. Patterns of metastasis to organs beyond the most common site (lung) are poorly characterised and it is unknown whether specific associations between patterns of metastatic progression and patient features exist. This retrospective study characterised the necropsy findings of 83 dogs receiving standardised therapy and clinical monitoring in a prospective clinical trial setting to document patterns of metastasis and correlate outcomes with these patterns and other patient and tumour-specific factors. A total of 20 different sites of metastasis were documented, with lung as the most common site, followed by bone, kidney, liver, and heart. Two distinct clusters of dogs were identified based on patterns of metastasis. There was no significant association between site of enrollment, trial arm, sex, serum alkaline phosphatase (ALP) activity, or tumour location and clinical outcomes. A second cancer type was identified at necropsy in 10 dogs (10/83; 12%). These data showcase the extensive nature of osteosarcoma metastasis beyond the lung and provide a benchmark for clinical monitoring of the disease. Further, this study provides insight into transcriptional features of primary tumours that may relate to a propensity for osteosarcoma metastasis to specific organs and tissues.

Propranolol blocks osteosarcoma cell cycle progression, inhibits angiogenesis and slows xenograft growth in combination with cisplatin-based chemotherapy

Osteosarcoma is still associated with limited response to standard-of-care therapy and alarmingly elevated mortality rates, especially in low- and middle-income countries. Despite multiple efforts to repurpose β-blocker propranolol in oncology, its potential application in osteosarcoma management remains largely unexplored. Considering the unsatisfied clinical needs of this aggressive disease, we evaluated the antitumoral activity of propranolol using different in vitro and in vivo osteosarcoma preclinical models, alone or in addition to chemotherapy. Propranolol significantly impaired cellular growth in β2-adrenergic receptor-expressing MG-63 and U-2OS cells, and was capable of blocking growth-stimulating effects triggered by catecholamines. siRNA-mediated ADRB2 knockdown in MG-63 cells was associated with decreased cell survival and a significant attenuation of PPN anti-osteosarcoma activity. Direct cytostatic effects of propranolol were independent of apoptosis induction and were associated with reduced mitosis, G0/G1 cell cycle arrest and a significant down-regulation of cell cycle regulator Cyclin D1. Moreover, colony formation, 3D spheroid growth, cell chemotaxis and capillary-like tube formation were drastically impaired after propranolol treatment. Interestingly, anti-migratory activity of β-blocker was associated with altered actin cytoskeleton dynamics. In vivo, propranolol treatment (10 mg/kg/day i.p.) reduced the early angiogenic response triggered by MG-63 cells in nude mice. Synergistic effects were observed in vitro after combining propranolol with chemotherapeutic agent cisplatin. Sustained administration of propranolol (10 mg/kg/day i.p., five days a week), alone and especially in addition to low-dose metronomic cisplatin (2 mg/kg/day i.p., three times a week), markedly reduced xenograft progression. After histological analysis, propranolol and cisplatin combination resulted in low tumor mitotic index and increased tumor necrosis. β-blockade using propranolol seems to be an achievable and cost-effective therapeutic approach to modulate osteosarcoma aggressiveness. Further translational studies of propranolol repurposing in osteosarcoma are warranted.