M2 muscarinic receptor: a new target to counteract human glioblastoma cell growth and survival

Gruppo di Ricerca: 
Di Bari M, Tombolillo V, Alessandrini F, Conte C, Ferretti M, Tata AM
Attach English: 

Glioblastoma is the most aggressive form of brain tumors in human. The high growth potential and decreased susceptibility to apoptosis of the glioma cells depend on high heterogeneity of cell populations and the presence of genetic mutations in several pro-apoptotic genes.

Muscarinic receptors are expressed in different primary and metastatic tumors and are implicated in their growth and propagation.

We have characterized the effects induced by M2 receptor activation on cell growth and survival in two different glioblastoma cell lines (U251MG and U87MG) and in primary cultures obtained from different human biopsies. M2 muscarinic receptors are expressed in glioblastoma human specimens and in glioblastoma cell lines. Cell growth analysis  has demonstrated that the M2 agonist arecaidine strongly decreased cell proliferationin both glioma cell lines and in primary cultures. This effect was dose and time dependent. FACS analysis has confirmed cell cycle arrest at G1/S and at G2/M phase in U87 and U251 respectively. To explain the ability of M2 agonist to inhibit glioblastoma cell proliferation we are evaluating the ability of M2 receptor to counteract the pathways usually up-regulated in glioma cells: Notch-1 and EGFR. Real time PCR and western blot analysis have demonstrated that M2 receptor causes a decreased expression of EGFR and Notch-1 expression, suggesting that the decreased cell proliferation may dependent on down-regulated expression and activity of these receptors. In particular in U251 cells we have also observed that M2 agonist causes a downregulation of Notch-1 ligands (e.g. delta-1, jagged-1 and -2) and of the transcription factor Hes-1.

The M2 receptor activation induces also a severe apoptosis. In particular in U251 cells we have observed that M2 agonist causes a genotoxic effects inducing ROS production, double strand DNA damage, the formation of multipolar mitotic spindles and misalignment of chromosomes.

Further analysis are in progress to also investigate the effects of M2 agonist on glioma cancer stem cells.

In conclusion we demonstrate that M2 receptor activation may have a relevant role in the inhibition of glioma cell growth and survival suggesting that these receptors may be a new interesting therapeutic targets to investigate for glioblastoma  therapy also considering that glioma cells show a chemosensitivity to arecaidine comparable to temozolomide that at least represents the gold standard in glioblastoma therapy.

Anno del Convegno: 
2012

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