No abstract

The search for new drugs and treatment approaches is of particular importance for glioblastomas (GBMs), as with other types of malignant gliomas, as they are lethal without the available medical care. Current anticancer cocktails have failed to prolong survival beyond 1 year, in part owing to the natural resistance of GBM cells and to the toxic side effects of the available drugs. In many organisms, cell death can be induced by cytolysins, which are proteins that can form pores in biological membranes. Perhaps by facilitating drugs to enter into the cytosol, cytolysins might be used to increase the efficacy of conventional anticancer agents. Here, the cytotoxicity of two sea anemone pore-forming cytolysins, toxin Bc2, and equinatoxin (EqTx-II) were investigated. Toxin Bc2 and EqTx-II were cytotoxic against human U87 and A172 GBM cell lines either wild type or p53 mutant, a tumor suppressor frequently mutated in malignant gliomas. Moreover, noncytotoxic concentrations of Bc2 or EqTx-II potentiated the cytotoxicity induced by low dose concentrations of all classical chemotherapeutics agents tested: cytosine arabinoside, doxorubicin, and vincristine. In comparison with the cytotoxicity induced by each of these classical anticancer drugs alone, 10-300-fold less of the therapeutic drug was needed when combined with the cytolysins. These results are promising, since lower concentrations of chemotherapeutic drugs could reduce the adverse effects of chemotherapy.

Gliomas, the most frequent primitive central nervous system tumors, have been suggested to originate from astrocytes or from neural progenitors/stem cells. However, the precise identity of the cells at the origin of gliomas remains a matter of debate because no pre-neoplastic state has been yet identified. Transforming growth factor (TGF)-a, an epidermal growth factor family member, is frequently overexpressed in the early stages of glioma progression. We previously demonstrated that prolonged exposure of astrocytes to TGF-a is sufficient to trigger their reversion to a neural progenitor-like state. To determine whether TGF-a dedifferentiating effects are associated with cancerous transforming effects, we grafted intracerebrally dedifferentiated astrocytes. We show that these cells had the same cytogenomic profile as astrocytes, survived in vivo, and did not give birth to tumors. When astrocytes dedifferentiated with TGF-a were submitted to oncogenic stress using gamma irradiation, they acquired cancerous properties: they were immortalized, showed cytogenomic abnormalities, and formed high-grade glioma-like tumors after brain grafting. In contrast, irradiation did not modify the lifespan of astrocytes cultivated in serum-free medium. Addition of TGF-a after irradiation did not promote their transformation but decreased their lifespan. These results demonstrate that reversion of mature astrocytes to an embryonic state without genomic manipulation is sufficient to sensitize them to oncogenic stress. STEM

Conclusions: In our study, no significant association between p53 expression and MDR functional phenotype was observed in ALL, CLL, and AML. On the other hand, a significant association (P ‫؍‬ 0.0003) of the coexpression was observed in CML. The p53 overexpression was more frequently seen in the accelerated phase and the blastic phase of this disease. Our results suggest that an MDR functional phenotype could be associated with p53 mutation in the advanced stage of leukemias.

This study aimed to investigate the antitumor and immunomodulatory properties of the flavonoid apigenin (5,7,4'-trihydroxyflavone), which was extracted from Croton betulaster Mull, in glioma cell culture using the high-proliferative rat C6 glioma cell line as a model. Apigenin was found to have the ability to reduce the viability and proliferation of C6 cells in a time-dependent and dose-dependent manner, with an IC50 of 22.8 µmol/l, 40 times lower than that of temozolomide (1000 µmol/l), after 72 h of apigenin treatment. Even after C6 cells were treated with apigenin for 48 h, high proportions of C6 cells entered apoptosis (39.56%) and autophagy (22%) as shown by flow cytometry using annexin V/propidium iodide and acridine orange staining, respectively. In addition, the flavonoid apigenin induced cell accumulation in the G0/G1 phase of the cell cycle and inhibited glioma cell migration efficiently. Moreover, apigenin induced astroglial differentiation and morphological changes in C6 cells, characterized by increased expression of glial fibrillary acidic protein and decreased expression of nestin protein, a typical marker of neuronal precursors. The immunomodulating effects of apigenin were also characterized by a change in the inflammatory profile as evidenced by a significant decrease in interleukin-10 and tumor necrosis factor production and increased nitric oxide levels. Because apigenin can induce differentiation, apoptosis, and autophagy, can alter the profile of cytokines involved in regulating the immune response, and can reduce the survival, growth, proliferation, and migration of C6 cells, this flavonoid may be considered a potential antitumor drug for the adjuvant treatment of malignant gliomas.

Multidrug resistance in gliomas is the major challenges in the clinical setting. We investigated the expression of P-glycoprotein (Pgp) and multidrug resistance-related protein 1 (MRP1) in 50 gliomas using immunohistochemistry. Compared to Pgp, MRP1 positivity was observed in highest percentage of gliomas grade IV samples (p = 0.008). Unlike MRP1 expression observed in high-grade, gliomas grade II exhibited a greater number of Pgp positive samples as compared to grades III and IV (p = 0.026). Our results suggest that the difference between the histological grade gliomas regarding MRP1 and Pgp expression must have implications in the choice of chemotherapeutic protocols.

TGFalpha and its receptor EGFR participate in the development of a wide range of tumors including gliomas, the main adult primary brain tumors. TGFalpha soluble form results from the cleavage by the metalloprotease TACE/ADAM17 of the extracellular part of its transmembrane precursor, pro-TGFalpha. To gain insights into the mechanisms underlying TGFalpha bioavailability, a yeast two-hybrid screen was performed to identify proteins interacting with pro-TGFalpha intracellular domain (ICD). DLG1/SAP97 (Discs Large Gene 1 or Synapse Associated Protein 97) was found to interact with both pro-TGFalpha and TACE ICDs through distinct PDZ domains. An in vivo pro-TGFalpha-DLG1-TACE complex was detected in U251 glioma cells and in gliomas-derived tumor initiating cells. Interaction between DLG1 and TACE diminished in response to stimulations promoting pro-TGFalpha shedding. Manipulation of DLG1 levels revealed dual actions of DLG1 on pro-TGFalpha shedding, favoring approximation of pro-TGFalpha and TACE, while limiting TACE full shedding activity. These results show that DLG1 participates in the control of TGFalpha bioavailability through its dynamic interaction with the growth factor precursor and TACE.

Laryngeal squamous cell carcinoma (LSCC) is the most common among several types of head and neck cancers. Current treatments have a poor effect on early and advanced cases, and further investigations for novel agents against LSCCs are desirable. In this study, we elucidate the cytotoxic enhancing effect of arsenic trioxide (As2O3) combined with L-buthionine sulfoximine (BSO) in LSCC. The effect of BSO with As2O3 or Cisplatin (CDDP) on cell viability was examined using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The reactive oxygen species (ROS) levels, cell cycle, and apoptosis were measured by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), propidium iodide (PI) and annexin V/PI. The acidic vacuolar organelles were visualized by fluorescence microscope and quantified using flow cytometry. Neither CDDP nor As2O3 when used alone reduced the cell viability. BSO was found to enhance only As2O3 sensitivity, leading to G2/M arrest and autophagy with no correlation of ROS induction. This result suggests that modulation of glutathione enhances autophagy, which interplays with apoptosis. In this study, we obtained initial preclinical evidence for the potential efficacy of these drugs in a combined therapy protocol.