Paclitaxel-releasing mesenchymal stromal cells inhibit in vitro proliferation of human mesothelioma cells

Introduction: Malignant pleural mesothelioma (MPM) is a rare fatal asbestos-related malignancy originating in the mesothelial cells of the pleura. A platinum-based doublet containing a third-generation antifolate is the front-line standard of care whilst there are no approved second-line treatments for MPM which remains a disease setting to test the efficacy of new therapeutic agents. Methods: Bone marrow mesenchymal stromal cells (BM-MSCs) were loaded with pemetrexed (PMX) and paclitaxel (PTX) according to a standardized procedure. Drug release by both PMX- and PTX-primed BMMSCs (BM-MSCs/PMX and BM-MSCs/PTX) was tested on the in vitro proliferation of a panel of tumor cell lines including NCI-H28 mesothelioma. Results: The in vitro anticancer activity of pure PTX was significantly higher than that of PMX against all the cell lines tested (14.7 times higher than that of PMX against NCI-H28). Whereas BM-MSCs did not take up and release PMX in amounts effective on mesothelioma, PTX-loaded BM-MSCs dramatically inhibited mesothelioma proliferation. Conclusions: PTX-primed mesenchymal stromal cells successfully inhibit the in vitro proliferation of human mesothelioma cells. Further studies and in vivo testing are required to confirm our preliminary in vitro results as a potential new mesothelioma therapy based on cell drug delivery.