Data represent mean SEM of three independent experiments in duplicate (*< 0.05 and **< 0.01, compared to untreated control). Notch1 as a mediator of metformin activities, were investigated. MPM cells showed high levels of Notch1 activation compared to normal pleural mesothelial cells. Furthermore, metformin treatment hampered MPM cell proliferation and enhanced the apoptotic process, accompanied by decreased Notch1 activation. and studies, have also shown an association between MPM and the oncogenic simian computer virus 40 (SV40), suggesting a transforming synergistic action between asbestos fibers and SV40 (Bocchetta et al., 2000; Carbone et al., 2008; Mazzoni et al., 2012; Rotondo et al., 2019). Furthermore, mutations in specific genes have been associated to the development of MPM, such as germline mutations/inactivations discovered in the tumor suppressor gene BRCA1-associated protein 1 (BAP1) in cases with a family history of cancer (Testa et al., 2011; Carbone et al., 2019). At present, Ifosfamide there is no effective remedy for MPM. There is therefore a growing interest in identifying novel approaches for early detection and an effective therapy for this deadly cancer. Metformin is the current first-line drug used in the treatment of type 2 diabetes mellitus (T2DM), with more than 120 million treated patients worldwide (Zi et al., 2018). Patients with untreated diabetes and T2DM have an increased malignancy risk, attributed mostly to the growth-promoting effect of chronic elevated plasma glucose and insulin levels (Giovannucci et Ifosfamide al., 2010; Noto et al., 2012). Insulin resistance and resultant hyperinsulinemia might indeed promote carcinogenesis directly through the insulin receptor or indirectly by increasing the levels of insulin-like growth factor (IGF). The interest in potential anti-neoplastic and cancer preventive properties of metformin is based on numerous clinical studies that showed a significantly reduced incidence of neoplastic diseases and cancer mortality in diabetic patients treated with metformin compared to diabetic patients treated with other antidiabetic drugs (Mansouri and Mahmoodi, 2017). A recent study performed in T2DM patients found no association between treatment with metformin and survival in MPM patient. However, this retrospective cohort study was conducted with some restrictions and limitations represented by Ifosfamide a small sample FGF3 size of pleural or unspecified mesothelioma cases, and by missing data for tumor stage, histological subtype and smoking status. This means that the association between metformin treatment and survival to mesothelioma may be underestimated (Wu et al., 2016). There is evidence of a metformin-mediated regulation of Notch (Chen et al., 2015), a pathway dysregulated in MPM, thus suggesting a role for Notch in this cancer (Bocchetta et al., 2003). The Notch signaling pathway, a highly conserved evolutionary system involved in short-range intracellular communication, plays many key functions in the regulation of cell proliferation and survival (Bigas and Espinosa, 2018). In canonical Notch signaling, Notch ligands (i.e., Delta-like 1,4 and Jagged 1,2) bind to their receptors (Notch 1-4) in neighboring cells (Siebel and Lendahl, 2017) triggering an enzymatic cut, releasing Notch Intracellular Domain name (NICD), which transfers to the nucleus to regulate target genes (Bray and Gomez-Lamarca, 2018; Zi et al., 2018). Dysregulation of Notch in cancer onset/progression has been extensively investigated (Rizzo et al., 2008b; Kushwah et al., 2014; Brzozowa-Zasada et al., 2017). Specifically, elevated Notch-1 and reduced Notch-2 expression have been observed in mesothelioma cells compared to normal mesothelial cells (HM) (Graziani et al., 2008). Notch inhibition as potential approach to stop cancer progression is Ifosfamide being investigated in several types of tumors (Takebe et al., 2015; Tamagnone et al., 2018) and could represent also a new therapeutic strategy for MPM. Materials and Methods Cell Cultures Human MPM cell lines, MMP89 (sarcomatoid histotype) and IST-Mes2 (epithelioid histotype), obtained from the GMP Cells and Cultures Lender, National Malignancy Institute (ICLC, Genoa, Italy), were produced in DMEM Hams F12 (Lonza, Basel, Switzerland) supplemented with 10% fetal bovine serum, FBS (EuroClone, Milan, Italy). Primary pleural mesothelial cells (HM) were obtained from biopsies collected from non-oncologic patients affected by pneumothorax at the Surgical Clinic of the University/Hospital of Ferrara, Department of Thoracic Surgery. The study was approved by the County Ethics Committee, Ferrara. All subjects gave written informed consent in accordance with.