Optimization of a Luciferase-Expressing Non-Invasive Intrapleural Model of Malignant Mesothelioma in Immunocompetent Mice

Abstract

Malignant Pleural Mesothelioma (MPM) is an aggressive tumor of the pleural lining that is usually identified at advanced stages and resistant to current therapies. Appropriate pre-clinical mouse tumor models are of pivotal importance to study its biology. Usually, tumor cells have been injected intraperitoneally or subcutaneously. Using three available murine mesothelioma cell lines with different histotypes (sarcomatoid, biphasic, epithelioid), we have set up a simplified model of in vivo growth orthotopically by inoculating tumor cells directly in the thorax with a minimally invasive procedure. Mesothelioma tumors grew along the pleura and spread on the superficial areas of the lungs, but no masses were found outside the thoracic cavity. As observed in human MPM, tumors were highly infiltrated by macrophages and T cells. The luciferase-expressing cells can be visualized in vivo by bioluminescent optical imaging to precisely quantify tumor growth over time. Notably, the bioluminescence signal detected in vivo correctly matched the tumor burden quantified with classical histology. In contrast, the subcutaneous or intraperitoneal growth of these mesothelioma cells was considered either non-representative of the human disease or unreliable to precisely quantify tumor load. Our non-invasive in vivo model of mesothelioma is simple and reproducible, and it reliably recapitulates the human disease.

Important functional role of the protein osteopontin in the progression of malignant pleural mesothelioma

“…As confirmed by histological examinations, tumors developed along the pleura surface, further spreading and colonizing the most peripheral areas of the lungs, without forming any neoplastic mass outside the thoracic cavity. Importantly, acquisition over time of the bioluminescent signal from Luc-transduced cells was totally trustable as it perfectly correlated with the quantification of tumor areas detected with conventional histology (44).…”

“…BALB/c mice 8 weeks-old were purchased from Charles River. The procedures for the syngeneic orthotopic mouse model have been previously described (44). AB1 and AB22 MPM cells were injected intra-thoracically.…”

“…Four mesothelioma surgical samples and their corresponding normal tissues were used for low-density array (LDA) analysis as previously described (44). The relative amount of each target gene mRNA to the mean of the five housekeeping genes (HPRT, 18S, GAPDH, B2M, and ACTB) was calculated as 2 -DCt , where DCt = Ct -Ct mean of housekeeping genes .…”

“…We next studied the in vivo growth of shOPN AB1 and AB22 engineered cells. As described by Digifico et al (44), we set up an orthotopic model of murine mesothelioma that recapitulates the human MPM. In this model, direct intra-thorax injection of tumor cells was performed with a minimally invasive procedure.…”

Use of preclinical models for malignant pleural mesothelioma

“… 106–114 Very few studies have used direct implantation of murine mesothelioma lines into the pleural space of mice. 113 In addition, all these murine mesothelioma cell lines were in fact established from peritoneal mesothelioma following intraperitoneal injection of asbestos. 107 112 115 While peritoneal and pleural mesothelioma might share some of the same biology, this has yet to be proved.…”