Valproic acid increases the in vitro effects of nitrosureas on human glioma cell lines.

Valproic acid (VPA) has been recently investigated for its anticancer properties in different tumors, including malignant gliomas. The aim of the present work was to evaluate the effects of VPA, alone or in combination with other chemotherapeutic drugs, on in vitro growth of human glioma cell lines. A172, U373, U138, U87, and SW1783 were treated with VPA alone or in combination with mitoxantrone, etoposide, or 1,3-bis(2-chloroethyl)-l-nitrosourea (BCNU). The effects of treatments on cell growth were assessed with crystal violet staining and analyzed using the combination index (CI). The percentage of apoptotic cells and the DNA content for cell cycle phases detection were also investigated by flow cytometry. Despite a certain variability, glioma cell lines were rather resistant to the drugs tested. Addition of VPA decreased the IC50 of the chemotherapeutic agents in all cell lines tested. This effect was more evident with BCNU. The synergic effect of the association of VPA and BCNU was related to an increased block of cell cycle with accumulation in S-G2/M phases of cell cycle rather than an increased programmed cell death. In our experimental model, VPA showed anticancer properties per se on human glioma cell lines and our data support the hypothesis that, if used in association with conventional chemotherapy, it might improve the effects of single chemotherapeutic agents.

In vitro study of low molecular weight heparin effect on cell growth and cell invasion in primary cell cultures of high-grade gliomas.

Heparins represent the first choice for prevention and treatment of venous thromboembolism. In particular, low molecular weight heparins (LMWHs) provide pharmacokinetic advantages compared to unfractionated heparin (UFH): longer half-life, better bioavailability, and lower binding to plasma proteins. In the last years results of preclinical and clinical studies have suggested that LMWH may be able to inhibit cell growth, cell invasion, and angiogenesis, which are key mechanisms involved in tumor progression, possibly influencing favorable clinical outcome in at least a proportion of cancer patients. In this work we investigated the effect of LMWH (enoxaparin) on cell growth and cell invasion in primary cell cultures obtained from high-grade glioma specimens: 5 anaplastic astrocytoma (AA) and 13 glioblastoma multiforme (GBM). Apoptosis and expression of the thrombin receptor PAR1 were also assessed. A significant decrease in tumor cell growth was observed after treatment with 10 U/ml (-21%; p = 0.001) and 100 U/ml (-26%; p < 0.001); tumor cells from AA (grade III; WHO) were more affected by LMWH treatment compared to cell lines from GBM (grade IV; WHO). The antiproliferative effect was more pronounced in cell cultures displaying higher expression of PAR1. Glioma cell cultures were able to invade a model of basement membrane (Matrigel matrix) in standard culture conditions, but migration was not modulated significantly by LMWH treatment at any of the concentrations tested (1, 10, 100 U/ml). In conclusion, our results confirm the antineoplastic effect of LMWH, suggesting a potential direct role on tumor cell growth in high grade gliomas.

In vitro effects of topotecan and ionizing radiation on TRAIL/Apo2L-mediated apoptosis in malignant glioma.

The survival of patients with malignant gliomas is still unsatisfactory despite multimodality treatment, therefore new therapeutic strategies are required. Tumor necrosis factor apoptosis related ligand (TRAIL/Apo2L), a member of the tumor necrosis factor superfamily, may induce apoptotic cell death in several tumors, but not in normal cells, upon binding with specific receptors. In the present study, the expression and function of TRAIL receptors (TRAIL-R1/DR4 and TRAIL-R2/DR5) has been investigated in five human glioma cell lines (U87, U138, U373, A172, SW1783) in ex vivo tumors and in primary cultures obtained from the tumors. Our data show that gliomas preferentially express TRAIL R2 and that treatment with topotecan, a topoisomerase I inhibitor, significantly up-regulates its expression as detected by flow cytometry and western blotting. Moreover, in most cases, treatment with topotecan resulted in an increased sensitivity to TRAIL-dependent apoptosis, although cyclohexymide had to be added to induce apoptosis. On glioma cell lines, the effects of irradiation on TRAIL receptors were also analysed. In our experimental conditions, irradiation with 2 Gy had a modest additive effect on TRAIL-dependent apoptosis and was not able to modulate TRAIL receptor expression.

Effect of association of temozolomide with other chemotherapic agents on cell growth inhibition in glioma cell lines.

Despite progresses in surgery and treatments of malignant gliomas, prognosis of these tumors remains poor, with a median life expectancy of 12 months in glioblastomas. Chemotherapy (mostly with nitrosoureas) has been demonstrated to prolong overall survival, but the entity of this improvement is slight and disease recurrence/progression is the rule, stressing the need for multimodality treatment. In this work we investigated the effect of association of temozolomide (TMZ), an orally bioavailable alkylating agent, with three chemotherapeutic drugs, liposomal doxorubicin (DOXO), cis-platinum (CDDP). and topotecan (TP), on cell growth of A 172, U373, U138, U87, and SW1783 (all human glioma cell lines). Results indicate a synergistic effect (CI < 1) of TMZ in association with liposomal DOXO and CDDP on cell growth inhibition in most of the studied cell lines (A172, U373, U138, U87). Synergistic effect also has been obtained after treatment of A 172 and U373 with TMZ and TP in association. In conclusion, our results confirm the potential effect of association of chemotherapic drugs with different mechanisms of action in the treatment of gliomas.