Type-3 metabotropic glutamate receptors regulate chemoresistance in glioma stem cells, and their levels are inversely related to survival in patients with malignant gliomas.

Drug treatment of malignant gliomas is limited by the intrinsic resistance of glioma stem cells (GSCs) to chemotherapy. GSCs isolated from human glioblastoma multiforme (GBM) expressed metabotropic glutamate receptors (mGlu3 receptors). The DNA-alkylating agent, temozolomide, killed GSCs only if mGlu3 receptors were knocked down or pharmacologically inhibited. In contrast, mGlu3 receptor blockade did not affect the action of paclitaxel, etoposide, cis-platinum, and irinotecan. mGlu3 receptor blockade enabled temozolomide toxicity by inhibiting a phosphatidylinositol-3-kinase/nuclear factor-κB pathway that supports the expression of O(6)-methylguanine-DNA methyltransferase (MGMT), an enzyme that confers resistance against DNA-alkylating agents. In mice implanted with GSCs into the brain, temozolomide combined with mGlu3 receptor blockade substantially reduced tumor growth. Finally, 87 patients with GBM undergoing surgery followed by adjuvant chemotherapy with temozolomide survived for longer time if tumor cells expressed low levels of mGlu3 receptors. In addition, the methylation state of the MGMT gene promoter in tumor extracts influenced survival only in those patients with low expression of mGlu3 receptors in the tumor. These data encourage the use of mGlu3 receptor antagonists as add-on drugs in the treatment of GBM, and suggest that the transcript of mGlu3 receptors should be measured in tumor specimens for a correct prediction of patients' survival in response to temozolomide treatment.

Type-3 metabotropic glutamate receptors negatively modulate bone morphogenetic protein receptor signaling and support the tumourigenic potential of glioma-initiating cells.

Targeted-therapies enhancing differentiation of glioma-initiating cells (GICs) are potential innovative approaches to the treatment of malignant gliomas. These cells support tumour growth and recurrence and are resistant to radiotherapy and chemotherapy. We have found that GICs express mGlu3 metabotropic glutamate receptors. Activation of these receptors sustained the undifferentiated state of GICs in culture by negatively modulating the action of bone morphogenetic proteins, which physiologically signal through the phosphorylation of the transcription factors, Smads. The cross-talk between mGlu3 receptors and BMP receptors was mediated by the activation of the mitogen-activated protein kinase pathway. Remarkably, pharmacological blockade of mGlu3 receptors stimulated the differentiation of cultured GICs into astrocytes, an effect that appeared to be long lasting, independent of the growth conditions, and irreversible. In in vivo experiments, a 3-month treatment with the brain-permeant mGlu receptor antagonist, LY341495 limited the growth of infiltrating brain tumours originating from GICs implanted into the brain parenchyma of nude mice. While clusters of tumour cells were consistently found in the brain of control mice, they were virtually absent in a large proportion of mice treated with LY341495. These findings pave the way to a new non-cytotoxic treatment of malignant gliomas based on the use of mGlu3 receptor antagonists.

Marginal donors in liver transplantation.

Marginal liver donor criteria included the following: obesity (weight >100 Kg or BMI >27), age >50 years; macrovesicular steatosis >50%; intensive care unit stay >4 days; prolonged hypotensive episodes of >1 hour, and <60 mm Hg with high inotropic drug use (dopamine, [DPM] > 14 microg/kg per minute); cold ischemia time >14 hours, peak serum sodium >155 mEq/L; sepsis, viral infections, and alcoholism; high levels of bilirubin, ALT, and AST, or extrahepatic neoplasia. Between August 1992 and May 2003, we performed 251 liver transplants in 241 patients of whom 155 are presently alive. We used 124 (49.4%) standard donors and 127 (50.6%) marginal donors. Among the group that received a standard donor, 81 (65.3%) are still alive. Among recipients of organs from marginal donors. 81 (63.8%) are still alive. We also assessed the quality of donors according to the severity of recipient disease. For standard donors these outcomes were 61.5% for UNOS 1, 37.5% for UNOS 2A, 73.2% for UNOS 2B, and 80% for UNOS 3 for marginal donors they were 46.1% for UNOS 1, 53.6% for UNOS 2A, 70.7% for UNOS 2B, and 63.6% for UNOS 3. Among the patients who received a liver from a donor >60 years old, there were no survivors in UNOS 1 and 2A, but there were good results in groups 2B and 3. These results suggest there is no difference between marginal and standard donors, even in sick patients, with the exception of donor age.