Glioblastoma multiforme y estudio de la resistencia a la quimioterapia mediada por transportadores ABC

Molecular mechanisms of resveratrol as chemo and radiosensitizer in cancer

One of the primary diseases that cause death worldwide is cancer. Cancer cells can be intrinsically resistant or acquire resistance to therapies and drugs used for cancer treatment through multiple mechanisms of action that favor cell survival and proliferation, becoming one of the leading causes of treatment failure against cancer. A promising strategy to overcome chemoresistance and radioresistance is the co-administration of anticancer agents and natural compounds with anticancer properties, such as the polyphenolic compound resveratrol (RSV). RSV has been reported to be able to sensitize cancer cells to chemotherapeutic agents and radiotherapy, promoting cancer cell death. This review describes the reported molecular mechanisms by which RSV sensitizes tumor cells to radiotherapy and chemotherapy treatment.

A2B Adenosine Receptor Enhances Chemoresistance of Glioblastoma Stem-Like Cells under Hypoxia: New Insights into MRP3 Transporter Function

Glioblastoma is the most common and aggressive primary brain tumor, characterized by its high chemoresistance and the presence of a cell subpopulation that persists under hypoxic niches, called glioblastoma stem-like cells (GSCs). The chemoresistance of GSCs is mediated in part by adenosine signaling and ABC transporters, which extrude drugs outside the cell, such as the multidrug resistance-associated proteins (MRPs) subfamily. Adenosine promotes MRP1-dependent chemoresistance under normoxia. However, adenosine/MRPs-dependent chemoresistance under hypoxia has not been studied until now. Transcript and protein levels were determined by RT-qPCR and Western blot, respectively. MRP extrusion capacity was determined by intracellular 5 (6)-Carboxyfluorescein diacetate (CFDA) accumulation. Cell viability was measured by MTS assays. Cell cycle and apoptosis were determined by flow cytometry. Here, we show for the first time that MRP3 expression is induced under hypoxia through the A2B adenosine receptor. Hypoxia enhances MRP-dependent extrusion capacity and the chemoresistance of GSCs. Meanwhile, MRP3 knockdown decreases GSC viability under hypoxia. Downregulation of the A_2B receptor decreases MRP3 expression and chemosensibilizes GSCs treated with teniposide under hypoxia. These data suggest that hypoxia-dependent activation of A_2B adenosine receptor promotes survival of GSCs through MRP3 induction.

Sphingosine-1-Phosphate in the Tumor Microenvironment: A Signaling Hub Regulating Cancer Hallmarks

As a key hub of malignant properties, the cancer microenvironment plays a crucial role intimately connected to tumor properties. Accumulating evidence supports that the lysophospholipid sphingosine-1-phosphate acts as a key signal in the cancer extracellular milieu. In this review, we have a particular focus on glioblastoma, representative of a highly aggressive and deleterious neoplasm in humans. First, we highlight recent advances and emerging concepts for how tumor cells and different recruited normal cells contribute to the sphingosine-1-phosphate enrichment in the cancer microenvironment. Then, we describe and discuss how sphingosine-1-phosphate signaling contributes to favor cancer hallmarks including enhancement of proliferation, stemness, invasion, death resistance, angiogenesis, immune evasion and, possibly, aberrant metabolism. We also discuss the potential of how sphingosine-1-phosphate control mechanisms are coordinated across distinct cancer microenvironments. Further progress in understanding the role of S1P signaling in cancer will depend crucially on increasing knowledge of its participation in the tumor microenvironment.

FK506 Attenuates the MRP1-Mediated Chemoresistant Phenotype in Glioblastoma Stem-Like Cells

Poor response to current treatments for glioblastoma has been attributed to the presence of glioblastoma stem-like cells (GSCs). GSCs are able to expel antitumor drugs to the extracellular medium using the multidrug resistance-associated protein 1 (MRP1) transporter. Tacrolimus (FK506) has been identified as an MRP1 regulator in differentiated glioblastoma (GBM) cells (non-GSCs); however, the effect of FK506 on GSCs is currently unknown. The objective of the following research is to evaluate the effect of FK506 on the MRP1-related chemo-resistant phenotype of GSCs. For this, U87MG and C6 glioma cell lines were used to generate non-GSCs and GSCs. mRNA and MRP1-positive cells were evaluated by RT-qPCR and flow cytometry, respectively. A Carboxyfluorescein Diacetate (CFDA)-retention assay was performed to evaluate the MRP1 activity. Apoptosis and MTT assays were employed to evaluate the cytotoxic effects of FK506 plus Vincristine (MRP1 substrate). GSC-derived subcutaneous tumors were generated to evaluate the in vivo effect of FK506/Vincristine treatment. No differences in transcript levels and positive cells for MRP1 were observed in FK506-treated cells. Lesser cell viability, increased apoptosis, and CFDA-retention in the FK506/Vincristine-treated cells were observed. In vivo, the FK506/Vincristine treatment decreased the tumor size as well as ki67, Glial Fibrillary Acidic Protein (GFAP), and nestin expression. We conclude that FK506 confers a chemo-sensitive phenotype to MRP1-drug substrate in GSCs.

Microglia/Astrocytes-Glioblastoma Crosstalk: Crucial Molecular Mechanisms and Microenvironmental Factors

In recent years, the functions of glial cells, namely, astrocytes and microglia, have gained prominence in several diseases of the central nervous system, especially in glioblastoma (GB), the most malignant primary brain tumor that leads to poor clinical outcomes. Studies showed that microglial cells or astrocytes play a critical role in promoting GB growth. Based on the recent findings, the complex network of the interaction between microglial/astrocytes cells and GB may constitute a potential therapeutic target to overcome tumor malignancy. In the present review, we summarize the most important mechanisms and functions of the molecular factors involved in the microglia or astrocytes-GB interactions, which is particularly the alterations that occur in the cell's extracellular matrix and the cytoskeleton. We overview the cytokines, chemokines, neurotrophic, morphogenic, metabolic factors, and non-coding RNAs actions crucial to these interactions. We have also discussed the most recent studies regarding the mechanisms of transportation and communication between microglial/astrocytes - GB cells, namely through the ABC transporters or by extracellular vesicles. Lastly, we highlight the therapeutic challenges and improvements regarding the crosstalk between these glial cells and GB.

Pro-apoptotic and anti-angiogenic properties of the α /β-thujone fraction from Thuja occidentalis on glioblastoma cells

The most aggressive type of brain tumor is glioblastoma multiforme, which to date remains incurable. Thuja occidentalis is used in homeopathy for the treatment of cancer, however, its mechanism of action remains unknown. We set out to study the effects of thujone fractions of Thuja on glioblastoma using in vitro and in vivo models. We found that the α/ β-thujone fraction decrease the cell viability and exhibit a potent anti-proliferative, pro-apoptotic and anti-angiogenic effects in vitro. In vivo assays showed that α /β-thujone promotes the regression of neoplasia and inhibits the angiogenic markers VEGF, Ang-4 and CD31 into the tumor.

Effect and mechanism of peroxisome proliferator-activated receptor-γ on the drug resistance of the U-87 MG/CDDP human malignant glioma cell line

Peroxisome proliferator-activated receptor-γ (PPAR-γ) is important in tumor differentiation, proliferation and apoptosis. However, the effect and mechanism of PPAR-γ on the promotion of cisplatin sensitivity in glioma cells remain to be elucidated. The present study established cisplatin-resistant U-87 MG/CDDP cell lines and U-87 MG/CDDP cell lines overexpressing PPAR-γ. With upregulated expression of PPAR-γ, the sensitivity of cancer cells to cisplatin was increased. Flow cytometry revealed that the intracellular content of rhodamine-123 was increased, expression of P-glycoprotein was downregulated, cell cycle was arrested in G0/G1 phase, apoptosis and oxidative stress was increased, levels of intracellular thymidylate synthase, glutathione and transforming growth factor-β1 were decreased, expression levels of multidrug resistance related gene (MDR), multidrug resistance-associated protein and glutothionine S-transferase-π were downregulated, expression levels of cell proliferation and apoptosis associated genes, including survivin and B-cell lymphoma-2, were downregulated, p53, p21 and caspase-3/8 were significantly upregulated, phosphorylation of extracellular signal-regulated kinase and small mothers against decapentaplegic 2 were downregulated, and the transcriptional activities of Twist and nuclear factor (erythroid-derived 2)-like 2 were significantly reduced. The results suggested that upregulation of PPAR-γ in the U-87 MG/DDP cells increased cisplatin sensitivity, and the underlying mechanisms included the regulation of MDR and apoptosis associated genes, which increased the intracellular accumulation of the drug, inhibited cell proliferation and promoted cell apoptosis.

Apoptosis-inducing effects of Melissa officinalis L. essential oil in glioblastoma multiforme cells

Current therapies for glioblastoma multiforme (GBM) are not effective. This study investigated the activity of the M. officinalis essential oil (EO) and its major component (citral) in GBM cell lines. Both EO and citral decreased the viability and induced apoptosis of GBM cells as demonstrated by DNA fragmentation and caspase-3 activation. Antioxidant prevented citral-induced death, indicating its dependence on the production of reactive oxygen species. Citral downmodulated the activity and inhibited the expression of multidrug resistance associated protein 1 (MRP1). These results show that EO, through its major component, citral, may be of potential interest for the treatment of GBM.

Current progress for the use of miRNAs in glioblastoma treatment

Glioblastoma (GBM) is a highly aggressive brain cancer with the worst prognosis of any central nervous system disease despite intensive multimodal therapy. Inevitably, glioblastoma is fatal, with recurrence of treatment-resistant tumour growth at distal sites leading to an extremely low median survival rate of 12-15 months from the time of initial diagnosis. With the advent of microarray and gene profiling technology, researchers have investigated trends in genetic alterations and, in this regard, the role of dysregulated microRNAs (highly conserved endogenous small RNA molecules) in glioblastoma has been studied with a view to identifying novel mechanisms of acquired drug resistance and allow for development of microRNA (miRNA)-based therapeutics for GBM patients. Considering the development of miRNA research from initial association to GBM to commercial development of miR-based therapeutics in less than a decade, it is not beyond reasonable doubt to anticipate significant advancements in this field of study, hopefully with the ultimate conclusion of improved patient outcome. This review discusses the recent advancements in miRNA-based therapeutic development for use in glioblastoma treatment and the challenges faced with respect to in vivo and clinical application.

5'-ectonucleotidase mediates multiple-drug resistance in glioblastoma multiforme cells

Glioblastoma multiforme (GBM) cells are characterised by their extreme chemoresistance. The activity of multiple-drug resistance (MDR) transporters that extrude antitumor drugs from cells plays the most important role in this phenomenon. To date, the mechanism controlling the expression and activity of MDR transporters is poorly understood. Activity of the enzyme ecto-5'-nucleotidase (CD73) in tumor cells, which hydrolyses AMP to adenosine, has been linked to immunosuppression and prometastatic effects in breast cancer and to the proliferation of glioma cells. In this study, we identify a high expression of CD73 in surgically resected samples of human GBM. In primary cultures of GBM, inhibition of CD73 activity or knocking down its expression by siRNA reversed the MDR phenotype and cell viability was decreased up to 60% on exposure to the antitumoral drug vincristine. This GBM chemosensitization was caused by a decrease in the expression and activity of the multiple drug associated protein 1 (Mrp1), the most important transporter conferring multiple drug resistance in these cells. Using pharmacological modulators, we have recognized the adenosine A(3) receptor subtype in mediation of the chemoresistant phenotype in these cells. In conclusion, we have determined that the activity of CD73 to trigger adenosine signaling sustains chemoresistant phenotype in GBM cells.

Antiglioma activity of curcumin-loaded lipid nanoparticles and its enhanced bioavailability in brain tissue for effective glioblastoma therapy

Glioblastoma, the most aggressive form of brain and central nervous system tumours, is characterized by high rates proliferation, migration and invasion. The major road block in the delivery of drugs to the brain is the blood-brain barrier, along with the expression of various multi-drug resistance (MDR) proteins that cause the efflux of a wide range of chemotherapeutic drugs. Curcumin, a herbal drug, is known to inhibit cellular proliferation, migration and invasion and induce apoptosis of glioma cells. It also has the potential to modulate MDR in glioma cells. However, the greatest challenge in the administration of curcumin stems from its low bioavailability and high rate of metabolism. To circumvent the above pitfalls of curcumin we have developed curcumin-loaded glyceryl monooleate (GMO) nanoparticles (NP) coated with the surfactant Pluronic F-68 and vitamin E D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) for brain delivery. We demonstrated that our curcumin-loaded NPs inhibit cellular proliferation, migration and invasion along with a higher percentage of cell cycle arrest and telomerase inhibition, thus leading to a greater percentage apoptotic cell death in glioma cells compared with native curcumin. An in vivo study demonstrated enhanced bioavailability of curcumin in blood serum and brain tissue when delivered by curcumin-loaded GMO NPs compared with native curcumin in a rat model. Thus, curcumin-loaded GMO NPs can be used as an effective delivery system to overcome the challenges of drug delivery to the brain, providing a new approach to glioblastoma therapy.