BMC Cancer Research article Characterization of human malignant mesothelioma cell lines orthotopically implanted in the pleural cavity of immunodeficient mice for their ability to grow and form metastasis Daniele Martarelli*1, Alfonso Catalano2, Antonio Procopio2, Sara Orecchia3, Roberta Libener3 and Giorgio Santoni1 BioMed Central Open Access Address: 1Department of Experimental Medicine and Public Health, University of Camerino, 62032 Camerino, Italy, 2Department of Molecular Pathology and Innovative Therapies, Polytechnic University of Marche, 60100, Ancona, Italy and Center of Cytology, Italian National Research Centers on Aging (INRCA – IRCCS), Ancona, Italy and 3Pathology Unit, Dept. Of Oncology, A.S.O. Alessandria, Italy Email: Daniele Martarelli* - daniele.martarelli@unicam.it; Alfonso Catalano - catgfp@yahoo.it; Antonio Procopio - procopio@mta01.unian.it; Sara Orecchia - saraorecchia@yahoo.it; Roberta Libener - rlibener@ospedale.al.it; Giorgio Santoni - giorgio.santoni@unicam.it * Corresponding author Published: 17 May 2006 BMC Cancer 2006, 6:130 doi:10.1186/1471-2407-6-130 This article is available from: http://www.biomedcentral.com/1471-2407/6/130 Received: 28 July 2005 Accepted: 17 May 2006 © 2006 Martarelli et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Malignant pleural mesothelioma (MPM) is a tumor known to be resistant to conventional therapies. Thus, an in vivo model can represent an important tool for assessing the efficacy of novel approaches in the treatment of MPM. Presently, human MPM cells have been grown orthotopically in mice upon transplantation of tumor masses or tumor cell suspensions following surgery. In these models however, surgery can interfere with the tumor growth and the early stages of tumor development cannot be easily explored. Finally, results may not be so accurate due to implantation of potentially different tumor samples in different experimental groups. Our work aimed at establishing a nude mouse model xenotransplanted with human MPM cell lines in which tumor progression exhibits some features of the human disease. Methods: Three distinct human MPM cell lines previously established from MPM patients displaying two different phenotypes, biphasic (MM-B1 and IST-Mes3) and epithelioid (IST-Mes2), were directly injected into the pleural cavity of nude mice. At different times, mice were sacrificed for autopsy, tumor nodules were counted and then removed for histology. Presence of metastases in visceral organs was also monitored. Results: IST-Mes2 cells were unable to grow in nude mice. MM-B1 and IST-Mes3 cells were capable of growing in nude mice and formed tumor nodules in the pleura. Post-mortem examination showed that MPM cells progressively colonized the parietal and visceral pleura, the diaphragm, the mediastinum and, lastly the lung parenchyma. No pneumo-thorax was evidenced in the mice. Pleural effusions as well as lymph node metastases were observed only at later times. Conclusion: This model mimics the progression of human malignant mesothelioma and it is easy to perform and reproducible; therefore it can be useful to study human MPM biology and evaluate the efficacy of novel therapies. Page 1 of 7 (page number not for citation purposes)