Paclitaxel-Loaded Expansile Nanoparticles in a Multimodal Treatment Model of Malignant Mesothelioma

Background. Malignant mesothelioma has a poor prognosis even when treated aggressively with multimodal therapy. Traditional murine tumor models can be used to evaluate drug efficacy and toxicity in malignant mesothelioma, but not to assess the effect of a multimodal approach that includes the surgical resection of tumor. We therefore developed a murine model of multimodal therapy in which we evaluated paclitaxel-loaded expansile nanoparticles (Pax-eNP) for delivering intracavitary chemotherapy in malignant mesothelioma. Methods. Paclitaxel-loaded expansile nanoparticles (Pax-eNP) of 100 nm, designed to release drug at an endosomal pH below 5, were synthesized. Xenografts of human malignant mesothelioma were established intraperitoneally in nude mice, followed by cytoreductive surgery (CRS) via laparotomy, and with omentectomy and resection of abdominal fat pads done 14 days later. At fascial closure, 10 mg/kg paclitaxel was delivered as traditional paclitaxel/paclitaxel Cremophor-EL (Pax-CE) or Pax-eNP. Morbidity and survival were assessed over a period of 90 days. Results. Cytoreductive surgery in mice was feasible and reproducible, and incurred less than 5% operative mortality. By itself, CRS did not significantly prolong survival; however, the addition of intraoperative Pax-CE or Pax-eNP significantly increased survival as compared with that of mice with untreated disease. In the case of Pax-eNP, the increase in survival was also statistically significant as compared with that following resection alone. Conclusions. A murine model of CRS for malignant mesothelioma allows the in vivo assessment of multimodal therapy, including nanoparticle delivery. Combination therapy was superior to no treatment or CRS alone in prolonging survival. Treatment with Pax-eNP improved overall survival in the setting of CRS, suggesting that Pax-eNP merits further evaluation for intracavitary drug delivery following the surgical resection of malignant mesothelioma.