In vivo imaging of human malignant mesothelioma grown orthotopically in the peritoneal cavity of nude mice

Malignant mesothelioma (MM) causes significant morbidity and mortality in patients. With increasing efforts devoted to developing therapeutics targeting mesothelioma, a xenograft mouse model with in vivo tumor imaging is especially desired for evaluating anti-tumor therapies. In the present study, we fluorescently labeled the NCI-H226 human mesothelioma cell line by a lentiviral vector harboring a luciferase-GFP (Luc/GFP) fusion gene driven by the RNA polymerase II promoter. After single-cell cloning by flow cytometry, a clone (named LMB-H226-GL) that stably expresses high levels of Luc/GFP was obtained. The in vivo tumorigenicity of Luc/GFP-labeled LMB-H226-GL was determined by using intraperitoneal injections of the cells in nude mice. LMB-H226-GL was found to be able to consistently form solid tumors in the peritoneum of mice. Tumor growth and aggressive progression could be quantitated via in vivo bioluminescence imaging. The model exhibited the pathological hallmarks consistent with the clinical progression of MM in terms of tumor growth and spread inside the peritoneal cavity. To evaluate the in vivo efficacy of drugs targeting mesothelioma, we treated mice with SS1P, a recombinant immunotoxin currently evaluated in Phase II clinical trials for treatment of mesothelioma. All the tumor-bearing mice had a significant response to SS1P treatment. Our results showed that this is a well-suited model for mesothelioma, and may be useful for evaluating other novel agents for mesothelioma treatment in vivo.