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Glioblastoma (GBM) is the most frequent malignant glioma. Treatment of GBM patients is multimodal with maximum surgical resection, followed by concurrent radiation and chemotherapy with the alkylating drug temozolomide (TMZ). The present study aims to identify genes implicated in the acquired resistance of two human GBM cells of astrocytic origin, T98G and U373, to TMZ. Resistance to TMZ was induced by culturing these cells in vitro for months with incremental TMZ concentrations up to 1 mM. Only partial resistance to TMZ has been achieved and was demonstrated in vivo in immunocompromised mice bearing orthotopic U373 and T98G xenografts. Our data show that long-term treatment of human astroglioma cells with TMZ induces increased expression of facilitative glucose transporter/solute carrier GLUT/SLC2A family members, mainly GLUT-3, and of the AKR1C family of proteins. The latter proteins are phase 1 drug-metabolizing enzymes involved in the maintenance of steroid homeostasis, prostaglandin metabolism, and metabolic activation of polycyclic aromatic hydrocarbons. GLUT-3 has been previously suggested to exert roles in GBM neovascularization processes, and TMZ was found to exert antiangiogenic effects in experimental gliomas. AKR1C1 was previously shown to be associated with oncogenic potential, with proproliferative effects similar to AKR1C3 in the latter case. Both AKR1C1 and AKR1C2 proteins are involved in cancer pro-proliferative cell chemoresistance. Selective targeting of GLUT-3 in GBM and/or AKR1C proteins (by means of jasmonates, for example) could thus delay the acquisition of resistance to TMZ of astroglioma cells in the context of prolonged treatment with this drug.

Gliomas account for more than 50% of all primary brain tumors. The worst prognosis is associated with gliomas of astrocytic origin, whereas gliomas with an oligodendroglial origin offer higher sensitivity to chemotherapy, especially when oligodendroglioma cells display 1p19q deletions. Temozolomide (TMZ) provides therapeutic benefits and is commonly used with radiotherapy in highly malignant astrocytic tumors, including glioblastomas. The actual benefits of TMZ during long-term treatment in oligodendroglioma patients have not yet been clearly defined. In this study, we have investigated the effects of such a long-term TMZ treatment in the unique Hs683 oligodendroglioma model. We have observed increased TMZ sensitivity of Hs683 orthotopic tumors that were previously treated in vitro with months of progressive exposure to increasing TMZ concentrations before being xenografted into the brains of immunocompromised mice. Whole-genome and proteomic analyses have revealed that this increased TMZ sensitivity of Hs683 oligodendroglioma cells previously treated for long periods with TMZ can be explained, at least partly, by a TMZ-induced p38-dependant dormancy state, which in turn resulted in changes in amino acid metabolism balance, in growth delay, and in a decrease in Hs683 oligodendroglioma cell-invasive properties. Thus, long-term TMZ treatment seems beneficial in this Hs683 oligodendroglioma model, which revealed itself unable to develop resistance against TMZ.

We have previously reported that galectin 1 (Gal-1) plays important biological roles in astroglial as well as in oligodendroglial cancer cells. As an oligodendroglioma model, we make use of the Hs683 cell line that has been previously extensively characterized at cell biology, molecular biology, and genetic levels. Galectin 1 has been shown to be involved in Hs683 oligodendroglioma chemoresistance, neoangiogenesis, and migration. Down-regulating Gal-1 expression in Hs683 cells through targeted small interfering RNA provokes a marked decrease in the expression of the brain-expressed X-linked gene: BEX2. Accordingly, the potential role of BEX2 in Hs683 oligodendroglioma cell biology has been investigated. The data presented here reveal that decreasing BEX2 expression in Hs683 cells increases the survival of Hs683 orthotopic xenograft-bearing mice. Furthermore, this decrease in BEX2 expression impairs vasculogenic mimicry channel formation in vitro and angiogenesis in vivo, and modulates glioma cell adhesion and invasive features through the modification of several genes previously reported to play a role in cancer cell migration, including MAP2, plexin C1, SWAP70, and integrin beta(6). We thus conclude that BEX2 is implicated in oligodendroglioma biology.

Several naphthalimides have been evaluated clinically as potential anticancer agents. UNBS3157, a naphthalimide that belongs to the same class as amonafide, was designed to avoid the specific activating metabolism that induces amonafide's hematotoxicity. The current study shows that UNBS3157 rapidly and irreversibly hydrolyzes to UNBS5162 without generating amonafide. In vivo UNBS5162 after repeat administration significantly increased survival in orthotopic human prostate cancer models. Results obtained by the National Cancer Institute (NCI) using UNBS3157 and UNBS5162 against the NCI 60 cell line panel did not show a correlation with any other compound present in the NCI database, including amonafide, thereby suggesting a unique mechanism of action for these two novel naphthalimides. Affymetrix genome-wide microarray analysis and enzyme-linked immunosorbent assay revealed that in vitro exposure of PC-3 cells to UNBS5162 (1 microM for 5 successive days) dramatically decreased the expression of the proangiogenic CXCL chemokines. Histopathology additionally revealed antiangiogenic properties in vivo for UNBS5162 in the orthotopic PC-3 model. In conclusion, the present study reveals UNBS5162 to be a pan-antagonist of CXCL chemokine expression, with the compound displaying antitumor effects in experimental models of human refractory prostate cancer when administered alone and found to enhance the activity of taxol when coadministered with the taxoid.

Although the molecular function of sigma receptors has not been fully defined and the natural ligand(s) is still not known, there is increasing evidence that these receptors and their ligands might play a significant role in cancer biology. 4-(N-benzylpiperidin-4-yl)-4-iodobenzamide (4-IBP), a selective sigma1 agonist, has been used to investigate whether this compound is able to modify: 1) in vitro the migration and proliferation of human cancer cells; 2) in vitro the sensitivity of human glioblastoma cells to cytotoxic drugs; and 3) in vivo in orthotopic glioblastoma and non-small cell lung carcinoma (NSCLC) models the survival of mice co-administered cytotoxic agents. 4-IBP has revealed weak antiproliferative effects on human U373-MG glioblastoma and C32 melanoma cells but induced marked concentration-dependent decreases in the growth of human A549 NSCLC and PC3 prostate cancer cells. The compound was also significantly antimigratory in all four cancer cell lines. This may result, at least in U373-MG cells, from modifications to the actin cytoskeleton. 4-IBP modified the sensitivity of U373-MG cells in vitro to proapoptotic lomustin and proautophagic temozolomide, and markedly decreased the expression of two proteins involved in drug resistance: glucosylceramide synthase and Rho guanine nucleotide dissociation inhibitor. In vivo, 4-IBP increased the antitumor effects of temozolomide and irinotecan in immunodeficient mice that were orthotopically grafted with invasive cancer cells.