MEDROXYPROGESTERONE ACETATE INDUCES C6 GLIOMA CHEMOSENSITIZATION VIA ANTIDEPRESSANT-LIKE LYSOSOMAL PHOSPHOLIPIDOSIS/MYELINOSISIN VITRO

Caprylic (Octanoic) Acid as a Potential Fatty Acid Chemotherapeutic for Glioblastoma

High grade glial tumors (HGGs) including anaplastic astrocytoma (WHO Grade-III) and glioblastoma multiforme (GBM, WHO Grade-IV) are among the most malignant cancers known to man. Due to their defective mitochondria, HGG cells consume glucose via glycolysis even in the presence of oxygen. Overall survival is worse in HGG patients that are hyperglycemic. Unlike normal neural cells, HGG cells cannot efficiently metabolize ketone bodies for energy. Thus, a metabolic treatment based on therapeutic ketosis (reduced glucose with elevated ketone bodies) was proposed to treat GBM and was supoported from preclinical studies. Caprylic (octanoic) acid, a monocarboxylated saturated fatty acid, is among the best producers of ketone bodies and induces necrosis of experimental tumors at high dose. Caprylic acid is enriched in coconut and in goat's milk. It is also a posttranslational modifier of the ghrelin hormone and is produced in trace amounts in human tissues. Caprylic acid is a straight-chain isomer of the antiepileptic valproic acid, which is used in treatment of HGG-associated seizures and which may increase survival in GBM patients according to epidemiological observations. Among the valproic acids analogs tested, caprylic acid is the most potent molecule to block C6 astrocytoma cell growth in vitro and accumulates selectively within glial cells as shown by Positron Emission Tomography in vivo. Caprylic acid blocks glycolysis both in healthy liver and in malignant liver cells, which is more prominent in the latter and also lowers blood glucose. Noteworthy, caprylic acid exerts neuroprotective- and mitochondria-protective effects in several models of neurodegenerative diseases. Boost injections of caprylic acid at non-toxic levels during classical ketogenic metabolic therapy may fortify antitumor actions and reduce systemic toxicity by differential programming of mitochondrial and other metabolic pathways.

Progesterone at high doses reduces the growth of U87 and A172 glioblastoma cells: Proteomic changes regarding metabolism and immunity

While pregnancy may accelerate glioblastoma multiforme (GBM) growth, parity and progesterone (P4) containing treatments (ie, hormone replacement therapy) reduce the risk of GBM development. In parallel, low and high doses of P4 exert stimulating and inhibitory actions on GBM growth, respectively. The mechanisms behind the high‐dose P4‐suppression of GBM growth is unknown. In the present study, we assessed the changes in growth and proteomic profiles when high‐dose P4 (100 and 300 µM) was administered in human U87 and A172 GBM cell lines. The xCELLigence system was used to examine cell growth when different concentrations of P4 (20, 50, 100, and 300 µM) was administered. The protein profiles were determined by two‐dimensional gel electrophoresis in both cell lines when 100 and 300 µM P4 were administered. Finally, the pathways enriched by the differentially expressed proteins were assessed using bioinformatic tools. Increasing doses of P4 blocked the growth of both GBM cells. We identified 26 and 51 differentially expressed proteins (fc > 2) in A172 and U87 cell lines treated with P4, respectively. Only the pro‐tumorigenic mitochondrial ornithine aminotransferase and anti‐apoptotic mitochondrial 60 kDa heat shock protein were downregulated in A172 cell line and U87 cell line when treated with P4, respectively. Detoxification of reactive oxygen species, cellular response to stress, glucose metabolism, and immunity‐related proteins were altered in P4‐treated GBM cell lines. The paradox on the effect of low and high doses of P4 on GBM growth is gaining attention. The mechanism related to the high dose of P4 on GBM growth can be explained by the alterations in detoxification mechanisms, stress, and immune response and glucose metabolism. P4 suppresses GBM growth and as it is nontoxic in comparison to classical chemotherapeutics, it can be used as a new strategy in GBM treatment in the future.

Gemcitabine, vinorelbine and cyclooxygenase inhibitors in the treatment of glioblastoma. Ultrastructural analyses in C6 glioma in vitro

OBJECTIVES

To define ultrastructural features accompanying to antitumor effects of gemcitabine, vinorelbine and cyclooxygenase inhibitors in C6 glioma cells in vitro. Vinorelbine is a semisynthetic vinca alkaloid and recent studies showed its antitumor activity in pediatric optic and pontine gliomas. Vinorelbine infusion induces a severe tumor site-pain in systemic cancers, but it is unknown whether algesia and inflammation contribute to its antitumor effects. Gemcitabine is a nucleoside-chemotherapeutic which was recently shown to act as a radiosensitizer in high-grade glioma. Some studies showed synergism of anti-inflammatory cyclooxygenase-inhibitors with microtubule inhibitors and gemcitabine. DMSO is a solvent and blocks both cylooxygenase and ribonucleotide reductase, another target of gemcitabine. Rofecoxib is withdrawn from the market, yet we used it for investigational purposes, since it blocks cylooxygenase-2 1000-times more potently than cylooxygenase -1 and is also a selective inhibitor of crinophagy.

METHODS

Plating efficacy, 3D-spheroid S-phase analysis with BrdU labelling and transmission electron microscopical analyses were performed.

RESULTS

Vinorelbine induced frequent mitotic slippage/apoptosis and autophagy. Despite both DMSO and rofecoxib induced autophagy alone and in synergy, they reduced mitotic catastrophe and autophagy triggered by vinorelbine, which was also reflected by reduced inhibition of spheroid S-phase. Gemcitabine induced karyolysis and margination of coarse chromatin towards the nuclear membrane, abundant autophagy, gutta adipis formation and decrease in mitochondria, which were enhanced by DMSO and rofecoxib.

CONCLUSIONS

Detailed ultrastructural analysis of the effects of chemotherapeutic drugs may provide a broader insight about their actions and pave to develop better strategies in treatment of glioblastoma.

From epidemiology and neurometabolism to treatment: Vitamin D in pathogenesis of glioblastoma Multiforme (GBM) and a proposal for Vitamin D + all-trans retinoic acid + Temozolomide combination in treatment of GBM

Here we review tumoricidal efficacy of Vitamin D analogues in glioblastoma multiforme (GBM) and potential synergisms with retinoic acid and temozolomide based on epidemiological and cellular studies. Epidemiological data suggest that winter birth is associated with higher risk of GBM, and GBM debulking in the winter enhanced mortality, which may relate with lower exposure to sunlight essential to convert cholecalciferol to Vitamin D. Comparative studies on blood bank specimens revealed that higher prediagnosis levels of calcidiol are associated with lower risk of GBM in elderly men. Supplemental Vitamin D reduced mortality in GBM patients in comparison to nonusers. Expression of Vitamin D Receptor is associated with a good prognosis in GBM. Conversely, Vitamin D increases glial tumor synthesis of neutrophins NGF and NT-3, the low affinity neurotrophin receptor p75NTR, IL-6 and VEGF, which may enhance glioma growth. Antitumor synergisms between temozolomide and Vitamin D and Vitamin D with Vitamin A derivatives were observed. Hence, we hypothesize that Calcitriol + ATRA (All-Trans Retinoic Acid) + Temozolomide - CAT combination might be a safer approach to benefit from Vitamin D in the management of high-grade glial tumors. Adding acetazolomide to this protocol may reduce the risk of pseudotumor cerebri, as both Vitamin D and Vitamin A excess may cause intracranial hypertension; this approach may provide further benefit as acetazolomide also exhibits anticancer activity.

From epidemiology and neurodevelopment to antineoplasticity. Medroxyprogesterone reduces human glial tumor growth in vitro and C6 glioma in rat brain in vivo

OBJECTIVE

Glial tumor growth may accelerate during gestation, but epidemiological studies consistently demonstrated that parousity reduces life long risk of glial tumors. Pregnancy may also accelerate growth of medulloblastoma and meningioma, but parousity does not confer protection against these tumors. We were the first to show that medroxyprogesterone acetate (MPA) reduces rat C6 glioma growth in vitro. Now we aimed to determine the effects of MPA on human brain cancers (particularly glioblastoma) in vitro and C6 glioma in vivo.

PATIENTS AND METHODS

We evaluated the effects of MPA on: i) monolayer growth of human U87 and U251 glioblastoma, ii) 3D-spheroid growth and invasion of C6 rat glioma and human U251 glioma, iii) interactions with PI3-Kinase inhibitors and coxsackie-adenovirus receptor (CAR) in modifying 3D-spheroid invasion of glioma.

RESULTS

MPA at low doses (3.25-13 μM) insignificantly stimulated and at high doses (above 52 μM) strongly suppressed the growth of human U87 and U251 cells in vitro. MPA also binds to glucocorticoid receptors similar to dexamethasone (Dex) and unexpectedly, PI3-Kinase inhibitors at low doses suppressed anti-invasive efficacies of MPA and Dex. MPA exerted higher invasion-inhibitory effects on CAR-expressing human glioma cells. Lastly, MPA suppressed growth of C6 glioma implanted into rat brain.

CONCLUSION

Progesterone analogues deserve to be studied in future experimental models of high grade glial brain tumors.