okadaic-acid and Glioblastoma

Cordycepin, a nucleoside-derivative-isolated form Cordyceps militaris, has been reported to suppress tumor cell proliferation and cause apoptosis. This study investigates the effect of cordycepin on the migration of human glioblastoma cells. Cordycepin suppressed the migration of the human glioblastoma cell lines U87MG and LN229 in transwell and wound healing assays. Cordycepin decreased protein expression of integrin α1, focal adhesion kinase (FAK), p-FAK, paxillin and p-paxillin. The lysosomal inhibitor NH

Topics: Ammonium Chloride; Animals; Antineoplastic Agents; Apoptosis; Brain Neoplasms; Cell Line, Tumor; Cell Movement; Deoxyadenosines; Enzyme Activation; Enzyme Inhibitors; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Lysosomes; Marine Toxins; Mice, Nude; Neoplasm Proteins; Okadaic Acid; Oxazoles; Phosphoprotein Phosphatases; Proteolysis; Tumor Burden; Xenograft Model Antitumor Assays

Nuclear receptor corepressor (N-CoR) is a critical regulator of neural stem cell differentiation. Nuclear localization of N-CoR is a feature of undifferentiated neural stem cells and cytoplasmic translocation of N-CoR leads to astrocytic differentiation. Comparative proteomic analysis of microdissected glioblastoma multiforme (GBM) specimens and matched normal glial tissue reveals increased expression of N-CoR in GBM. In GBM primary cell cultures, tumor cells with nuclear localization of N-CoR demonstrate an undifferentiated phenotype, but are subject to astroglial differentiation upon exposure to agents promoting phosphorylation of N-CoR and its subsequent translocation to the cytoplasm. Treatment of glioma cell lines with a combination of retinoic acid and low-dose okadaic acid decreases the corepressor effect of N-CoR and has a striking synergistic effect on growth inhibition. The identification of N-CoR in GBM provides insights into the tumorigenesis process and supports the development of differentiation-based therapeutic strategies.

Topics: Biomarkers; Brain Neoplasms; Cell Differentiation; Cell Proliferation; Drug Synergism; Glioblastoma; Humans; Neoplastic Stem Cells; Nuclear Proteins; Nuclear Receptor Co-Repressor 1; Okadaic Acid; Phosphorylation; Protein Transport; Repressor Proteins; Signal Transduction; Tretinoin; Tumor Cells, Cultured

The challenging possibility of selectively inducing mitotic death in tumor cells by combining genotoxic agents with the inhibition of G2 checkpoints of the cell cycle is the subject of intensive investigation. We show that very low concentrations (3.5 and 5 nM) of okadaic acid induce mitotic death in two glioblastoma cell lines, in the absence of genotoxic agents. At the concentrations used, the main target of okadaic acid action is protein phosphatase 2A (PP2A), an enzyme deeply involved in the negative control of cell-cycle progression. The peculiar susceptibility of glioblastoma cells to induction of mitotic death by very low concentrations of okadaic acid must be related to an impairment of PP2A activity and to a specific deficiency in some cell-cycle checkpoints. In addition to its ability to induce abnormal mitoses in actively proliferating glioblastoma cells, okadaic acid possesses the ability to force semi-confluent glioblastoma cells to the M phase of the cell cycle, where they show the same abnormalities observed in actively proliferating glioblastoma cells. In semi-confluent cells the induction of mitotic death involves the activity of both the extracellular signal regulated kinases (ERKs) and the M-phase promoting factor: okadaic acid overstimulates ERK activity, and PD98059 (inhibitor of ERK activation) as well as roscovitine (S)-isomer (specific inhibitor of M-phase promoting factor activity) counteract the induction of mitotic death. Our results show that, without the use of genotoxic agents, it is possible to induce mitotic death in glioblastoma cells by activating the same uncontrolled pathways responsible for the uncontrolled proliferation.

Topics: Apoptosis; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Flow Cytometry; Fluorescent Antibody Technique; Glioblastoma; Humans; Mitosis; Okadaic Acid; Phosphoprotein Phosphatases; Protein Phosphatase 2