PLEIOTROPIC EFFECTS OF PERIFOSINE ON GLIOBLASTOMA CELLS SURVIVAL: ALTERED MEMBRANE LIPID METABOLISM AND CELL SIGNALING
Tesi di Dottorato
Data di Pubblicazione:
2016
Citazione:
PLEIOTROPIC EFFECTS OF PERIFOSINE ON GLIOBLASTOMA CELLS SURVIVAL: ALTERED MEMBRANE LIPID METABOLISM AND CELL SIGNALING / A. Cinque ; tutor: P. Viani ; coordinatore: M. Locati. DIPARTIMENTO DI BIOTECNOLOGIE MEDICHE E MEDICINA TRASLAZIONALE, 2016 Feb 18. 28. ciclo, Anno Accademico 2015. [10.13130/cinque-alessandra_phd2016-02-18].
Abstract:
Glioblastoma multiforme (GBM) is the most frequent and aggressive malignant tumor of the central nervous system in adults. Despite decades of experimentation to improve the outcome of patients with GBM, this type of neoplasm remains one of the most lethal human cancers.Therefore, the need to test different and new agents for efficacy and safety is urgent. Perifosine (PF) is a synthetic lipid analogue belonging to a relatively new class of structurally related antitumor agents: the alkylphospholipids (APLs). PF exhibits potent antineoplastic activity against a multitude of cancer cell lines and different tumor models and is currently being tested in phase II clinical trial against major human tumors. However, the effect of PF against gliomas is poorly investigated. PF can induce apoptosis and/or cell growth arrest in tumor cells, but the details of its molecular mechanism is still to be elucidated. To date, the Ser/Thr kinase Akt, which is a key regulator of multiple survival pathways, is considered as the most important molecular target of PF.
However, PF can induce also Akt-independent effects and the contribution of Akt inhibition to the clinical activity of PF remains to be assessed. As other ALPs, PF may alter the structure and function of cell membranes directly by inducing a biophysical disturbance of cell membranes where it accumulates and/or indirectly by interfering with the metabolism and transport of membrane lipids. In particular, alterations in the properties of lipid rafts, ordered membrane lipid domains enriched in cholesterol and sphingolipids (SLs), could affect numerous signaling pathways crucial to cell survival and proliferation that are dependent on these structures.
On these premises, the purpose of this study was to investigate the sensitivity of GBM cells to PF treatment and to provide a contribution to the understanding of its molecular mechanism by focusing on the ability of PF to target membrane lipid metabolism and content, and, as a consequence, membrane-related signaling pathways crucial in the regulation of cell demise.
At first, we evaluated the effect of PF on cell survival in several human GBM cell lines. We demonstrated that in these cell lines PF inhibits cell viability in a dose-dependent manner and that its cytotoxic effects are not solely due to Akt inhibition. Furthermore, we found that in glioma cells PF maintains ERK in its phosphorylated/active state in a sustained manner over time. Treatment with the MAPK inhibitor PD98059 potentiates PF toxicity, and strongly reduces PF-induced LC3B-II increase. This could thus represent a molecular mechanism for self-defense from PF, at least in part due to the induction of protective autophagy. Moreover, in cells exposed to PF we found a time-dependent increase in the number of giant and multinucleated cells with an irregular shape, these morphological changes resembling those described for mitotic catastrophe, suggesting that this could be the mechanism of PF-induced cells death, while apoptosis was undetectable.
Accumulating literature indicates that in several tumor cell lines PF inhibits the rate limiting step of phosphatidylcholine (PC) synthesis, which is catalyzed by CTP:phosphocholine cytidylyltransferase, and this was associated to cell death with still unclear mechanisms. Furthermore, PC is the donor of phosphocholine in the reaction catalyzed by the enzyme sphingomyelin synthase (SMS), so the inhibition of the PC biosynthesis may also affect the sphingomyelin (SM) biosynthesis from ceramide (Cer). We found that also in GBM cells PF affects PC biosynthesis. In addition, in our model PF inhibits SM biosynthesis by affecting SMS activity, and the reduced PC seems not to represent a limiting factor for SM synthesis. The decreased utilizatio
Tipologia IRIS:
Tesi di dottorato
Elenco autori:
A. Cinque
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