piperidines and Oligodendroglioma

In this study, the role of the endothelin B receptor (ETBR) in oligodendroglioma cell proliferation and survival was investigated in vitro and in vivo. The overexpression and knockdown of ETBR was conducted in Hs683 human oligodendroglioma cells, and cell proliferation and activation (phosphorylation) of extracellular signal-regulated kinase (ERK) were measured in vitro. An orthotopic xenograft oligodendroglioma mouse model was established. Mouse survival times and immunohistochemical Ki67 staining in the xenografts were examined. In vitro experiments demonstrated that the overexpression of ETBR significantly enhanced the proliferation of oligodendroglioma cells and the activation of ERK compared with the controls, which was eliminated by the selective ETBR inhibitor BQ788 and ERK-specific inhibitor U0126, but not selective endothelin A receptor inhibitor BQ123. By contrast, the knockdown of endogenous ETBR markedly decreased oligodendroglioma cell proliferation and the activation of ERK compared with the controls. Overexpression of ETBR significantly increased immunohistochemical Ki67 staining in the Hs683 cell orthotopic xenograft and decreased animal survival. By contrast, knockdown of ETBR significantly decreased Ki67 staining and increased mouse survival times. Intratumoral injection of BQ788, but not BQ123, significantly decreased Ki67 staining and prolonged mouse survival times. In conclusion, ETBR was demonstrated to mediate the proliferation of oligodendroglioma cells according to an ERK-dependent mechanism. Using an orthotopic xenograft oligodendroglioma mouse model, it was demonstrated in vivo that ETBR promotes oligodendroglioma proliferation and that the selective ETBR antagonist effectively inhibits the proliferation of oligodendroglioma cells and prolongs survival times. This study provides a novel insight into the role of ETBR in oligodendroglioma proliferation and survival, and provides the first in vivo evidence that ETBR-specific antagonists are a potential therapeutic alternative for oligodendrogliomas.

Topics: Animals; Butadienes; Cell Line, Tumor; Cell Survival; Endothelin B Receptor Antagonists; Extracellular Signal-Regulated MAP Kinases; Humans; Kaplan-Meier Estimate; Ki-67 Antigen; Mice; Mice, Nude; Nitriles; Oligodendroglioma; Oligopeptides; Piperidines; Receptor, Endothelin B; RNA Interference; RNA, Small Interfering; Transplantation, Heterologous

Endothelin-1 (ET-1), a vasoactive and mitogenic peptide mainly produced by vascular endothelial cells, may be involved in the progression of several human tumors. Here, we present an immunohistochemical analysis of the expression pattern of ET-1 receptor subtypes (ET(A)-R and ET(B)-R) and a functional study of their potential role in human oligodendrogliomas and oligoastrocytomas. By comparison, we assessed the corresponding expression patterns of glioblastomas. Interestingly, a nuclear localization of ET-1 receptor subtypes (associated or not with a cytoplasmic labeling) was constantly observed in tumor cells from all three glioma types. Moreover, we noted a distinct receptor distribution in the different gliomas: a nuclear expression of ET(B)-R by tumor cells was found to be restricted to oligodendrogliomas and oligoastrocytomas, while a nuclear expression of ET(A)-R was only detected in tumor cells from some glioblastomas. Using primary cultures of oligodendroglial tumor cells, we confirmed the selective expression of nuclear ET(B)-R, together with a plasma membrane expression, and further demonstrated that this receptor was functionally coupled to intracellular signaling pathways known to be involved in cell survival and/or proliferation: extracellular signal-regulated kinase and focal adhesion kinase activation, actin cytoskeleton reorganization. In addition, impairment of ET(B)-R activation in these cells by in vitro treatment with an ET(B)-R-specific antagonist induced cell death. These data point to ET-1 as a possible survival factor for oligodendrogliomas via ET(B)-R activation and suggest that ET(B)-R-specific antagonists might constitute a potential therapeutic alternative for oligodendrogliomas.

Topics: Actin Cytoskeleton; Antihypertensive Agents; Astrocytoma; Brain Neoplasms; Cell Membrane; Cell Nucleus; Cell Survival; Cytoplasm; Endothelin B Receptor Antagonists; Endothelin-1; Extracellular Signal-Regulated MAP Kinases; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Glioblastoma; Humans; Immunohistochemistry; Oligodendroglioma; Oligopeptides; Piperidines; Protein-Tyrosine Kinases; Receptor, Endothelin A; Receptor, Endothelin B; Tumor Cells, Cultured