Abstract 4237: Drug-releasing mesenchymal cells strongly suppress B16 lung metastasis in a syngeneic murine model
Authors: Alessandri Giulio , Leonetti Carlo , Artuso Simona , Orlandi Augusto , Passeri Daniela , Benetti Anna , Berenzi Angiola , Dessy Enrico , Pascucci Luisa , Ceccarelli Piero , Bonomi Arianna , Coccè Valentina , Portolani Nazario , Ceserani Valentina , Parati Eugenio , Pessina Augusto 
Published: August 2015

Abstract
Mesenchymal stromal cells (MSCs) are considered an important therapeutic tool in cancer therapy. Because MSCs may home tumor microenvironment they have the possibility to directly delivery molecules to cancer cells. We have demonstrated that MSCs, upon in vitro priming with anti-cancer drug, become drug-releasing mesenchymal cells (Dr-MCs) able to strongly inhibit cancer cells growth. In order to expand our studies we here investigated whether intravenous (i.v) injection of MSCs loaded with Paclitaxel (PTX) were able to reduce B16 melanoma lung metastasis formation. To this end, as Dr-MCs, the murine MSC line SR4987 was used. SR4987 cells were loaded with PTX (SR4987PTX) by incubating for 24h with 2000ng/ml PTX. The anti-metastatic activity of SR4987PTX was evaluated in mice injected i.v. with 2.5 × 105 B16 melanoma cells. Tracking of the SR4987 in the lung was studied by immunohistochemistry using anti-Sca-1 antibodies. Adhesion and migration experiments were performed to elucidated the mechanism of SR4987PTX homing. In summary, we found that three i.v. injections of SR4987PTX on day 5, 10 and 15 after tumor injection almost completely (&gt;90% inhibition) abolished B16 lung metastasis. This effect was significantly superior (p&lt;0.01) than PTX given at the maximal tolerated dose of 10mg/Kg. SR4987PTX arrested into lung by interacting with endothelium and migrate toward cancer nodule through a complex mechanism involving primarily mouse lung stromal cells (mL-StCs). Indeed in vitro data show that mL-StCs treated with the conditioned medium (CM) of B16 cells (B16-CM) increase adhesion of SR4987PTX on lung endothelium (L-MECs) and stimulated their migration. In this contest the addition of the inflammatory cytokine TNFα enhanced both adhesion and migration of SR4987PTX. Additionally, we found that mL-StCs induce migration of SR4987PTX through the release SDF-1. Indeed, blocking SDF-1 activity by using anti-SDF-1 antibodies or its receptors CXCR4/CXCR7 with the compound AMD3100, migration of SR4987PTX was strongly reduced. In vivo SDF-1 expression was increased in mL-StCs surrounding metastases, while the presence of Sca-1+ cells nearby metastasis as well in the infiltrating microvessels confirmed the cancer homing capability of SR4987PTX. In conclusion, because it is known that cancer recruits circulating MSCs to form its stroma, it is proposed to exploit this property to fight it, by administrating exogenous MSCs carrying anticancer molecules. Our results show for the first time that Dr-MCs loaded with PTX are very effective as “Trojan horses” to delivery the drug and to strongly inhibit lung metastasis formation. Actually, a cure for lung metastasis in human is mostly unlikely, we think that our approach of using Dr-MCs loaded with PTX may represent a new valid and additive therapeutic tool to fight metastases and, perhaps, lung cancers in human.
Citation Format: Giulio Alessandri, Carlo Leonetti, Simona Artuso, Augusto Orlandi, Daniela Passeri, Anna Benetti, Angiola Berenzi, Enrico Dessy, Luisa Pascucci, Piero Ceccarelli, Arianna Bonomi, Valentina Coccè, Nazario Portolani, Valentina Ceserani, Eugenio Parati, Augusto Pessina. Drug-releasing mesenchymal cells strongly suppress B16 lung metastasis in a syngeneic murine model. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4237. doi:10.1158/1538-7445.AM2015-4237