d-609 and Glioma

Glioma Stem-like Cells (GSCs) isolated from patient derived tumors have high metabolic activity and survive in the absence of exogenous growth factors. We recently demonstrated that acute D609 (Tricyclodecan-9-yl-xanthogenate), a PC-PLC inhibitor with anti-oxidative property, can decrease the ATP content & GADD45β protein in GSCs cultured without growth factors, but not in the presence of growth factors. In this study we examined the effect of chronic D609 treatment on GSCs cultured in complete medium containing growth factors. Our results show that chronic exposure of GSCs to D609 decreased the ATP content and reduced the expression of GADD45β protein. Furthermore, cyclin D1 content and the phosphorylation of retinoblastoma protein also diminished, resulting in the arrest of cells in G1 phase of cell cycle after D609 treatment. In addition, the expression of Olig2, a protein responsible for the progression of glioblastoma was reduced by D609. Together these results indicate that chronic D609 treatment can inhibit the growth of glioma cells by arresting cells in G1 phase of cell cycle and/or reducing Olig2 expression.

Topics: Antigens, Differentiation; Antineoplastic Agents; Bridged-Ring Compounds; Cell Cycle; Down-Regulation; Gene Expression Regulation, Neoplastic; Glioma; Humans; Molecular Targeted Therapy; Neoplastic Stem Cells; Norbornanes; Oligodendrocyte Transcription Factor 2; Phosphorylation; Thiocarbamates; Thiones; Time Factors

The mechanism of action of 2-hydroxyoleic acid (2OHOA), a potent antitumor compound, has not yet been fully elucidated. Here, we show that human cancer cells have markedly lower levels of sphingomyelin (SM) than nontumor (MRC-5) cells. In this context, 2OHOA treatment strongly augments SM mass (4.6-fold), restoring the levels found in MRC-5 cells, while a loss of phosphatidylethanolamine and phosphatidylcholine is observed (57 and 30%, respectively). The increased SM mass was due to a rapid and highly specific activation of SM synthases (SMS). This effect appeared to be specific against cancer cells as it did not affect nontumor MRC-5 cells. Therefore, low SM levels are associated with the tumorigenic transformation that produces cancer cells. SM accumulation occurred at the plasma membrane and caused an increase in membrane global order and lipid raft packing in model membranes. These modifications would account for the observed alteration by 2OHOA in the localization of proteins involved in cell apoptosis (Fas receptor) or differentiation (Ras). Importantly, SMS inhibition by D609 diminished 2OHOA effect on cell cycle. Therefore, we propose that the regulation of SMS activity in tumor cells is a critical upstream event in 2OHOA antitumor mechanism, which also explains its specificity for cancer cells, its potency, and the lack of undesired side effects. Finally, the specific activation of SMS explains the ability of this compound to trigger cell cycle arrest, cell differentiation, and autophagy or apoptosis in cancer cells.

Topics: Apoptosis; Bridged-Ring Compounds; Cell Cycle Checkpoints; Cell Differentiation; Cell Line, Tumor; Cell Membrane; Cell Survival; Cell Transformation, Neoplastic; Cells; fas Receptor; Gene Expression Regulation, Enzymologic; Glioma; Humans; Immunoblotting; Jurkat Cells; Membrane Microdomains; Membrane Proteins; Nerve Tissue Proteins; Norbornanes; Oleic Acids; Phosphodiesterase Inhibitors; ras Proteins; Reverse Transcriptase Polymerase Chain Reaction; Sphingomyelins; Thiocarbamates; Thiones; Transferases (Other Substituted Phosphate Groups)