Pharmacological blockade of mGlu2/3 metabotropic glutamate receptors reduces cell proliferation in cultured human glioma cells

Abstract

Glial cell proliferation in culture is under the control of metabotropic glutamate (mGlu) receptors. We have examined whether this control extends to human glioma cells. Primary cultures were prepared from surgically removed human glioblastomas. RT-PCR combined with western blot analysis showed that most of the cultures (eight out of 11) expressed group-II mGlu receptors. In two selected cultures (MZC-12 and FCN-9), the mGlu2/3 receptor antagonist, LY341495, slowed cell proliferation when applied to the growth medium from the second day after plating. This effect was reversible because linear cell growth was restored after washing out the drug. LY341495 reduced glioma cell proliferation at concentrations lower than 100 nM, which are considered as selective for mGlu2/3 receptors. In addition, its action was mimicked by the putative mGlu2/3 receptor antagonist (2S)-a-ethylglutamate. The anti-proliferative effect of LY341495 was confirmed by measuring [methyl-3 H]-thymidine incorporation in cultures arrested in G 0 phase of the cell cycle and then stimulated to proliferate by the addition of 10% fetal calf serum or 100 ng/mL of epidermal growth factor (EGF). In cultures treated with EGF, LY341495 was also able to reduce the stimulation of the mitogen-activated protein kinase (MAPK) pathway, as well as the induction of cyclin D1. Both effects, as well as decreased [methyl-3 H]-thymidine incorporation, were partially reduced by co-addition of the potent mGlu2/3 receptor agonist, LY379268. We conclude that activation of group-II mGlu receptors supports the growth of human glioma cells in culture and that antagonists of these receptors should be tested for their ability to reduce tumour growth in vivo.

Metabotropic Glutamate Receptors in Glial Cells

“…mGlu receptors are expressed in glioma cell lines, as well as in cells isolated from malignant gliomas [19,24,87,88]. In contrast to what observed in cultured astrocytes, activation of mGlu3 receptors supports proliferation of glioma cells [87]. Accordingly, a chronic treatment with group II mGlu receptor antagonists reduces the growth of glioma cells in vivo, indicating that mGlu2/3 antagonists are of potential use in the experimental treatment of malignant gliomas [88].…”

“…The expression of mGlu5 receptors in enteric glial cells is increased in colitis suggesting a potential role for mGlu5 receptors in the pathophysiology of this disorder [86]. mGlu receptors are expressed in glioma cell lines, as well as in cells isolated from malignant gliomas [19,24,87,88]. In contrast to what observed in cultured astrocytes, activation of mGlu3 receptors supports proliferation of glioma cells [87].…”

The Excitatory Amino Acid Transporter-2 Induces Apoptosis and Decreases Glioma Growth In vitro and In vivo

“…Several studies have shown that N -methyl-D-aspartate, a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, and G proteincoupled glutamate receptors are located on tumor cells with an astrocytic lineage (13)(14)(15)(16). Astrocytic tumor cells that release glutamate might stimulate tumor cell proliferation and motility via autocrine or paracrine activation of glutamate receptors.…”

“…Antagonism of N-methyl-D-aspartate and a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid glutamate receptors has been shown to decrease tumor cell proliferation via decreased cell division (14). Likewise, pharmacologic antagonism of glutamate G proteincoupled receptors decreased glioma cell proliferation in vitro (13), suggesting that some tumors are sensitive to glutamate antagonists. Excess glutamate could also facilitate invasion by causing excitotoxic damage to normal brain.…”

Metabotropic Glutamate Receptors in Peripheral Tissues: Implications for Toxicology

“…Nevertheless, over-expression of mGluR4 was associated with poor prognosis in colorectal carcinoma (Chang et al, 2005) and their expression was identified in 68% of colorectal carcinomas, 50% of laryngeal carcinomas, and 46% of breast carcinomas (Julio-Pieper et al, 2011). Concordant with the expression profile, pharmacological blockade of mGluR3 reduces cell proliferation and mitogen-activated protein kinase activation in cultured human glioma explants or glioma cell lines (D'Onofrio et al, 2003). Furthermore, systemic administration of the mGluR2/3 antagonist LY341495 inhibits the growth of glioma cells implanted either under the skin or inside the brain parenchyma of nude mice (Arcella et al, 2005).…”