Glioblastoma multiforme (GBM) is the most frequent and malignant type of brain tumor. GBM is one of the abundant vasculature tumors and microvessel density correlates to high invasiveness and treatment resistance. Malignant gliomas are characterized by cellular heterogeneity. In particular, the presence of an undifferentiated cell population defined Glioblastoma Stem Cells (GSCs) has been reported. GSCs are considered the main cell population responsible for the beginning of the development of neoplastic process and recurrence formation. Several studies indicate that GSCs are able to differentiate into endothelial-like cells. These glioblastoma-derived endothelial cells are usually abnormal cells, generated by a process termed Vasculogenic Mimicry. This ability of GSCs correlates with increasing malignancy and aggressiveness of tumor. Previous studies performed in our laboratory have focused on the effects mediated by muscarinic receptors activation in GBM. In particular, we have analyzed the effects mediated by M2 receptor activation both in glioblastoma cell lines and in GSCs, obtained from human glioblastoma biopsies. The activation of muscarinic M2 receptor by orthosteric agonist Arecaidine Propargyl Ester (APE) caused a significant decrease of cell proliferation and survival (Ferretti et al, 2013; Di Bari et al, 2018). Recently we have tested a new dualsteric agonist for M2 receptor, N8-Iperoxo, that showed high selectivity and more efficiency than APE and that is able to activate M2 receptor at very low concentration (Cristofaro et al, 2018). Preliminary data also showed that M2 receptor was able to impair the in vitro vasculogenesis in Huvec. Starting from this evidence, in this project we will evaluate the ability of the N8-Iperoxo to negatively modulate neo-angiogenesis-GSCs derived. The impairment of GSCs differentiation into endothelial-like cells could represent an additional therapeutic strategy to counteract glioblastoma growth and invasiveness.
For the first time, ACh muscarinic receptors were characterized in human Glioblastoma stem cells. In order to find a new cancer treatment and knowing the role of M2 receptor in brain tumors, it appears relevant to understand the effects produced bty this receptor in cancer stem cells.
GSCs are considered responsible for tumor growth and invasiveness, they are able to evade the most common cancer therapies and they are considered the main cell population responsible for the beginning of the development of neoplastic process and of recurrence formation. The identification of new drugs able to inhibit the proliferation and survival of GSCs may represent a clinically relevant achievement in the field of anti-cancer therapy.
M2 muscarinic agonist APE is capable to arrest in glioblastoma cell lines and GSCs cell cycle progression with a significant decrease of cells in S phase. M2 receptor activation reduces cell survival, inducing a dramatic apoptosis in both cell lines. N8-Iperoxo, a new dualsteric agonist, is able to activate M2 receptor at lower doses than APE, reducing possible side effects. This makes it a more promising molecule than APE for potential glioblastoma treatment
Furthermore, GSCs can promote tumor angiogenesis and they have been demonstrated to be resistant to cell death following growth factors withdrawal. Vasculogenic mimicry has been observed in GBM and it has been implicated in invasion and metastasis. Understanding the mechanism of how GSCs differentiate into functional endothelium will be important for developing new therapeutic approaches for GBM treatment. The results obtained in the present project may contribute to better understand the potential effects mediated in particular by dualsteric agonist N8-Iperoxo not only on GSC growth and survival but also in neo-angiogenesis-GSC stimulated. The Identification of a potential drug able to impair in the same time the GSC survival and proliferation and the formation of new tumor vessels, may have a strategic relevance in clinical treatment of GBM.