gene silencing has an anti malignant effect on cell lines overexpressing mesothelin deriving from malignant pleural

Genes involved in the carcinogenetic mechanisms underlying malignant pleural mesothelioma (MPM) are still poorly characterized. So far, mesothelin (MSLN) has aroused the most interest. It encodes for a membrane glycoprotein, frequently over-expressed in various malignancies such as MPM, and ovarian and pancreatic cancers. It has been proposed as a diagnostic and immunotherapeutic target with promising results. However, an alternative therapeutic approach seems to rise, whereby synthetic molecules, such as antisense oligonucleotides, could be used to inhibit MSLN activity. To date, such a gene-level inhibition has been attempted in two studies only, both on pancreatic and ovarian carcinoma cell lines, with the use of silencing RNA approaches. With regard to MPM, only one cell line (H2373) has been employed to study the effects of MSLN depletion. Indeed, the knowledge on the role of MSLN in MPM needs expanding. Accordingly, we investigated the expression of MSLN in a panel of three MPM cell lines, i.e. NCI-H28, Mero-14, and IstMes2; one non-MPM cell line was used as reference (Met5A). MSLN knock-down experiments on MSLN-overexpressing cells were also performed through silencing RNA (siRNA) to verify whether previous findings could be generalized to a different set of cell cultures. In agreement with previous studies, transient MSLN-silencing caused decreased proliferation rate and reduced invasive capacity and sphere formation in MSLN-overexpressing Mero-14 cells. Moreover, MSLN-siRNA combined with cisplatin, triggered a marked increase in apoptosis and a decrease in proliferation as compared to cells treated with each agent alone, thereby suggesting a sensitizing effect of siRNA towards cisplatin. In summary, our findings confirm that MSLN should be considered a key molecular target for novel gene-based targeted therapies of cancer. Citation: Melaiu O, Stebbing J, Lombardo Y, Bracci E, Uehara N, et al. (2014) MSLN Gene Silencing Has an Anti-Malignant Effect on Cell Lines Overexpressing Mesothelin Deriving from Malignant Pleural Mesothelioma. PLoS ONE 9(1): e85935. doi:10.1371/journal.pone.0085935 Editor: Mitchell Ho, National Cancer Institute, NIH, United States of America Received September 5, 2013; Accepted December 3, 2013; Published January 21, 2014 Copyright: 2014 Melaiu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was funded by the University of Pisa (www.unipi.it) (regular badget, ex 60%), and by the Fondazione Buzzi Unicem (www.buzziunicem.it). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: slandi@biologia.unipi.it . These authors contributed equally to this work.