Valproic acid induced differentiation and potentiated efficacy of taxol and nanotaxol for controlling growth of human glioblastoma LN18 and T98G cells

Mocetinostat as a novel selective histone deacetylase (HDAC) inhibitor in the promotion of apoptosis in glioblastoma cell line C6 and T98G

Histon deacetylase (HDAC) enzyme is one of the enzymes involved in regulating gene expression and epigenetic alternation of cells by removing acetyl groups from lysine residue on a histone, allowing the histones to wrap the DNA more tightly and suppressing a tumor-suppressing gene. HDAC inhibitors play an important role in inhibiting the proliferation of tumor cells by restricting the mechanism of action of HDAC enzyme, leading to the addition of acetyl groups to lysine. Mocetinostat, also known by its chemical name (MGCD0103), is a novel isotype selective HDAC enzyme that explicitly targets HDAC isoforms inhibiting Class1(HDAC 1,2,3,8) and Class IV (HDAC11) enzymes. It was approved for treating the phase II trial of Hodgkin's lymphoma in 2010. Our study revealed that different doses of Mocetinostat inhibit the growth of glioblastoma cells, metastasis, and angiogenesis and induce the apoptosis and differentiation of glioblastoma cells C6 and T98G. Western blot has shown that MGCD0103 has many biological activities to control glioblastoma cancer cells. MGCD0103 can modulate the molecular mechanism for several pathways in cells, such as inhibition of the PI3K/AKT pathway and suppression of HDAC1 enzyme activity in charge of many biological processes in the initiation and progression of cancer. The high doses of Mocetinostat drug significantly induce apoptosis and suppress cancer cell proliferation through increased pro-apoptotic proteins (BAX) and a down level of anti-apoptotic proteins(Bid, Bcl2). Also, the mocetinostat upregulated the expression of the tumor suppressor gene and downregulated the gene expression of the E2f1 transcription factor. Additionally, MGCDO103-induced differentiation was facilitated by activating the differentiation marker GFAP and preventing the undifferentiation marker from expression (Id2, N-Myc). The MGCD0103 is a potent anticancer drug crucial in treating glioblastoma cells.

Emerging therapeutic potential of anti-psychotic drugs in the management of human glioma: A comprehensive review

Despite numerous advancements in the last decade, human gliomas such as astrocytoma and glioblastoma multiforme have the worst prognoses among all cancers. Anti-psychotic drugs are commonly prescribed to treat mental disorders among cancer patients, and growing empirical evidence has revealed their antitumor, anti-metastatic, anti-angiogenic, anti-proliferative, chemo-preventive, and neo-adjuvant efficacies in various in vitro, in vivo, and clinical glioma models. Anti-psychotic drugs have drawn the attention of physicians and researchers owing to their beneficial effects in the prevention and treatment of gliomas. This review highlights data on the therapeutic potential of various anti-psychotic drugs as anti-proliferative, chemopreventive, and anti-angiogenic agents in various glioma models via the modulation of upstream and downstream molecular targets involved in apoptosis, autophagy, oxidative stress, inflammation, and the cell cycle in in vitro and in vivo preclinical and clinical stages among glioma patients. The ability of anti-psychotic drugs to modulate various signaling pathways and multidrug resistance-conferring proteins that enhance the efficacy of chemotherapeutic drugs with low side-effects exemplifies their great potential as neo-adjuvants and potential chemotherapeutics in single or multimodal treatment approach. Moreover, anti-psychotic drugs confer the ability to induce glioma into oligodendrocyte-like cells and neuronal-like phenotype cells with reversal of epigenetic alterations through inhibition of histone deacetylase further rationalize their use in glioma treatment. The improved understanding of anti-psychotic drugs as potential chemotherapeutic drugs or as neo-adjuvants will provide better information for their use globally as affordable, well-tolerated, and effective anticancer agents for human glioma.

Valproate sensitizes human glioblastoma cells to 3-bromopyruvate-induced cytotoxicity

Glioblastoma (GBM) is the most common brain tumor; however, no effective treatment for it is available yet. Monocarboxylate transporters, which are highly expressed in GBM, play a role in transporting antitumor agents, such as 3-bromopyruvate (3-BrPA). Valproate, primarily used to treat epilepsy, has been considered a possible treatment option for malignant GBM. In this study, we aimed to investigate the combined effects of 3-BrPA and valproate on GBM cell growth and elucidate the underlying mechanisms. Valproate enhanced 3-BrPA-induced cell death in T98G cells, used as a GBM model. Multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) mRNA levels significantly increased after valproate treatment. 3-BrPA-induced cell death, which was enhanced by valproate, was inhibited in the presence of MK571, a MRP inhibitor, or Ko143, a BCRP inhibitor. In addition, treatment with 3-BrPA and valproate for 48 h reduced cellular ATP levels compared to those in the 3-BrPA alone treatment group. However, cellular ATP levels were recovered in the presence of MK571 or Ko143, compared to those in the 3-BrPA and valproate treatment groups. In conclusion, we suggested that valproate enhanced 3-BrPA-induced cell death. This might be attributable to the increase in cellular ATP consumption owing to valproate-induced MRP2 or BCRP expression.

Combination Therapy with Sulfasalazine and Valproic Acid Promotes Human Glioblastoma Cell Death Through Imbalance of the Intracellular Oxidative Response

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor and still lacks effective therapeutic strategies. It has already been shown that old drugs like sulfasalazine (SAS) and valproic acid (VPA) present antitumoral activities in glioma cell lines. SAS has also been associated with a decrease of intracellular glutathione (GSH) levels through a potent inhibition of xc- glutamate/cystine exchanger leading to an antioxidant deprotection. In the same way, VPA was recently identified as a histone deacetylase (HDAT) inhibitor capable of activating tumor suppression genes. As both drugs are widely used in clinical practice and their profile of adverse effects is well known, the aim of our study was to investigate the effects of the combined treatment with SAS and VPA in GBM cell lines. We observed that both drugs were able to reduce cell viability in a dose-dependent manner and the combined treatment potentiated these effects. Combined treatment also increased cell death and inhibited proliferation of GBM cells, while having no effect on human and rat cultured astrocytes. Also, we observed high protein expression of the catalytic subunit of xc- in all the examined GBM cell lines, and treatment with SAS blocked its activity and decreased intracellular GSH levels. Noteworthy, SAS but not VPA was also able to reduce the [¹⁴C]-ascorbate uptake. Together, these data indicate that SAS and VPA exhibit a substantial effect on GBM cell's death related to an intracellular oxidative response imbalance, making this combination of drugs a promising therapeutic strategy.

BIX01294, an inhibitor of histone methyltransferase, induces autophagy-dependent differentiation of glioma stem-like cells

Glioblastoma (GBM) contains rare glioma stem-like cells (GSCs) with capacities of self-renewal, multi-lineage differentiation, and resistance to conventional therapy. Drug-induced differentiation of GSCs is recognized as a promising approach of anti-glioma therapy. Accumulating evidence suggests that unique properties of stem cells depend on autophagy. Here we demonstrate that BIX01294, an inhibitor of a G9a histone methyltransferase (introducing H3K9me2 and H3K27me3 repressive marks) triggers autophagy in human glioma cells. Pharmacological or genetic inhibition of autophagy decreased LC3-II accumulation and GFP-LC3 punctation in BIX01294-treated cells. GSCs-enriched spheres originating from glioma cells and GBM patient-derived cultures express lower levels of autophagy related (ATG) genes than the parental glioma cell cultures. Typical differentiation inducers that upregulate neuronal and astrocytic markers in sphere cultures, increase the level of ATG mRNAs. G9a binds to the promoters of autophagy (LC3B, WIPI1) and differentiation-related (GFAP, TUBB3) genes in GSCs. Higher H3K4me3 (an activation mark) and lower H3K9me2 (the repressive mark) levels at the promoters of studied genes were detected in serum-differentiated cells than in sphere cultures. BIX01294 treatment upregulates the expression of autophagy and differentiation-related genes in GSCs. Pharmacological inhibition of autophagy decreases GFAP and TUBB3 expression in BIX01294-treated GSCs suggesting that BIX01294-induced differentiation of GSCs is autophagy-dependent.

Valproic acid promotes radiosensitization in meningioma stem-like cells

Although meningioma stem-like cells have been isolated and characterized, their therapeutic targeting remains a challenge. Meningioma sphere cells (MgSCs) with cancer stem cells properties show chemo- and radioresistance in comparison with meningioma adherent cells (MgACs). We tested the effect of valproic acid (VPA), a commonly used anti-epileptic drug, which passes the blood brain barrier, on cultured MgSCs. VPA reduced the viability of MgSCs and MgACs. In MgSCs, treatment with VPA increased radio-sensitivity, expression of p-cdc2, p-H2AX and cleaved caspase-3 and PARP. Anchorage-independent growth (AIG) was reduced by VPA. AIG was further reduced by combined treatment with irradiation. Expression of a stem cell marker, Oct4, was reduced by VPA. Oct4 was further decreased by combined treatment with irradiation. These results suggest that VPA may be a potential treatment for meningioma through targeting meningioma stem-like cells.

Downregulation of Nrf2 by the combination of TRAIL and Valproic acid induces apoptotic cell death of TRAIL-resistant papillary thyroid cancer cells via suppression of Bcl-xL

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) represents an effective agent for the treatment of many cancers, though the majority of thyroid cancers are found to be resistant. Therefore it would be necessary to identify agents capable of increasing the sensitivity of these cancers to TRAIL-mediated cell death. Here, we examined the therapeutic effect and its underlying mechanism of combination treatment of TRAIL and histone deacetylase inhibitor, Valproic acid (VPA) in vitro using human papillary thyroid cancer (PTC) cells and in vivo using an orthotopic mouse model of PTC. TRAIL-VPA combination therapy synergistically induced apoptotic cell death in TRAIL-resistant PTC through caspase activation. In addition, downregulation of antioxidant transcription factor, Nrf2 by co-treatment of TRAIL-VPA induces cell death via suppression of Bcl-xL in vitro and in vivo; these effects were further enhanced following siRNA inhibition of these proteins in combination with TRAIL or TRAIL-VPA. Taken together, VPA sensitized TRAIL-resistant PTC cells to apoptotic cell death through involvement of Nrf2 and Bcl-xL. Thus, the combination of VPA and TRAIL may be a promising therapy for TRAIL-resistant PTC.

EWS Knockdown and Taxifolin Treatment Induced Differentiation and Removed DNA Methylation from p53 Promoter to Promote Expression of Puma and Noxa for Apoptosis in Ewing's Sarcoma

Ewing’s sarcoma is a pediatric tumor that mainly occurs in soft tissues and bones. Malignant characteristics of Ewing’s sarcoma are correlated with expression of EWS oncogene. We achieved knockdown of EWS expression using a plasmid vector encoding EWS short hairpin RNA (shRNA) to increase anti-tumor mechanisms of taxifolin (TFL), a new flavonoid, in human Ewing’s sarcoma cells in culture and animal models. Immunofluorescence microscopy and flow cytometric analysis showed high expression of EWS in human Ewing’s sarcoma SK-N-MC and RD-ES cell lines. EWS shRNA plus TFL inhibited 80% cell viability and caused the highest decreases in EWS expression at mRNA and protein levels in both cell lines. Knockdown of EWS expression induced morphological features of differentiation. EWS shRNA plus TFL caused more alterations in molecular markers of differentiation than either agent alone. EWS shRNA plus TFL caused the highest decreases in cell migration with inhibition of survival, angiogenic and invasive factors. Knockdown of EWS expression was associated with removal of DNA methylation from p53 promoter, promoting expression of p53, Puma, and Noxa. EWS shRNA plus TFL induced the highest amounts of apoptosis with activation of extrinsic and intrinsic pathways in both cell lines in culture. EWS shRNA plus TFL also inhibited growth of Ewing’s sarcoma tumors in animal models due to inhibition of differentiation inhibitors and angiogenic and invasive factors and also induction of activation of caspase-3 for apoptosis. Collectively, knockdown of EWS expression increased various anti-tumor mechanisms of TFL in human Ewing’s sarcoma in cell culture and animal models.

Seizure prognosis in brain tumors: new insights and evidence-based management

Brain tumor-related epilepsy (BTE) is common in low- and high-grade gliomas. The risk of seizures varies between 60% and 100% among low-grade gliomas and between 40% and 60% in glioblastomas. The presence of seizures in patients with brain tumors implies favorable and unfavorable factors. New-onset seizures represent an early warning sign for the presence of a brain tumor and count as a good prognostic factor for survival. Recurrence or worsening of seizures during the course of disease may signal tumor progression. Each of the modalities for tumor control (i.e., surgery, radiotherapy, chemotherapy) contributes to seizure control. Nevertheless, one third of BTE shows pharmacoresistance to antiepileptic drugs (AEDs) and may severely impair the burden of living with a brain tumor. For symptomatic therapy of BTE, seizure type and individual patient factors determine the appropriate AED. Randomized controlled trials in partial epilepsy in adults to which type BTE belongs and additional studies in gliomas indicate that levetiracetam is the agent of choice, followed by valproic acid (VPA). In the case of recurring seizures, combining these two drugs (polytherapy) seems effective and possibly synergistic. If either one is not effective or not well tolerated, lacosamide, lamotrigine, or zonisamide are additional options. A new and exciting insight is the potential contribution of VPA to prolonged survival, particularly in glioblastomas. A practice guideline on symptomatic medical management including dose schedules of AEDs is supplied.

In vitro anticancer drug test: A new method emerges from the model of glioma stem cells

Glioblastoma multiforme (GBM) is a grade IV astrocytoma and the most common malignant brain tumor. Current therapies provide a median survival of 12–15 months after diagnosis, due to the high recurrence rate. The failure of current therapies may be due to the presence, within the tumor, of cells characterized by enhanced self-renewal capacity, multilineage differentiation potential and elevated invasive behavior, called glioma stem cells (GSCs). To evaluate the pharmacological efficacy of selected drugs on six GSC lines, we set up a multiple drug responsivity assay based on the combined evaluation of cytomorphological and functional parameters, including the analysis of polymorphic nuclei, mitotic index and cell viability. In order to understand the real pharmacological efficacy of the tested drugs, we assigned a specific drug responsivity score to each GSC line, integrating the data produced by multiple assays. In this work we explored the antineoplastic effects of paclitaxel (PTX), an inhibitor of microtubule depolymerization, utilized as standard treatment in several cancers, and of valproic acid (VPA), an inhibitor of histone deacetylases (HDACs) with multiple anticancer properties. We classified the six GSC lines as responsive or resistant to these drugs, on the basis of their responsivity scores. This method can also be useful to identify the best way to combine two or more drugs. In particular, we utilized the pro-differentiating effect of VPA to improve the PTX effectiveness and we observed a significant reduction of cell viability compared to single treatments.

The Beneficial Effects of Valproic Acid in Thyroid Cancer Are Mediated through Promoting Redifferentiation and Reducing Stemness Level: An In Vitro Study

Valproic acid (VPA) has been identified as a histone deacetylase inhibitor, inducing differentiation in transformed cells. However, no study has shown the effect of VPA in the redifferentiation induction and stemness of anaplastic thyroid. The main objective of this study was to evaluate the efficacy of VPA as a differentiation therapy agent in human thyroid cancer based on its effect on stemness and differentiation process. Indications for differentiation of 8305C and B-CPAP cell lines following VPA treatment were obtained by analyzing cell proliferation rate, morphological changes, adherent-dependent colony formation, and Hoechst 33342 staining. The expressions of stemness, differentiation, and aggressiveness specific marker genes were measured by quantitative RT-PCR. VPA treatment effectively showed growth inhibition in both cell lines. The high nuclear-cytoplasmic (N : C) ratio of 8305C cells markedly decreased and treated cells became more epithelial-like. Treated cells showed stronger Hoechst 33342 fluorescence compared with control cells. The hTERT and OCT-4 reduction was paralleled with adherent-dependent colony formation decrement in both cell lines. VPA effectively induced NIS and TTF-1 in anaplastic cells, it whereas showed no clear pattern in papillary cell line. VPA treatment also resulted in the reduction of MMP-2 and MMP-9. These finding suggest that VPA could redifferentiate the anaplastic thyroid cancer cells.

miR-138 overexpression is more powerful than hTERT knockdown to potentiate apigenin for apoptosis in neuroblastoma in vitro and in vivo

Decrease in expression of the tumor suppressor microRNA-138 (miR-138) correlates well with an increase in telomerase activity in many human cancers. The ability of almost all human cancer cells to grow indefinitely is dependent on presence of telomerase activity. The catalytic component of human telomerase reverse transcriptase (hTERT) regulates telomerase activity in most of the human cancers including malignant neuroblastoma. We observed an indirect increase in the expression of miR-138 after the transfection with hTERT short hairpin RNA (shRNA) plasmid in human malignant neuroblastoma SK-N-DZ and SK-N-BE2 cell lines. Transfection with hTERT shRNA plasmid followed by treatment with the flavonoid apigenin (APG) further increased expression of miR-138. Direct transfection with miR-138 mimic was more powerful than transfection with hTERT shRNA plasmid in potentiating efficacy of APG for decreasing cell viability and colony formation capability of both cell lines. Upregulation of miR-138 was also more effective than down regulation of hTERT in enhancing efficacy of APG for induction of apoptosis in malignant neuroblastoma cells in vitro and in vivo. We delineated that apoptosis occurred with induction of molecular components of the extrinsic and intrinsic pathways in SK-N-DZ and SK-N-BE2 cells both in vitro and in vivo. In conclusion, these results demonstrate that direct miR-138 overexpression is more powerful than hTERT down regulation in enhancing pro-apoptotic effect of APG for controlling growth of human malignant neuroblastoma in cell culture and animal models.

BMP4 reverses multidrug resistance through modulation of BCL-2 and GDNF in glioblastoma

Patients with glioblastoma are commonly treated with chemotherapy. But a significant proportion of patients develop disease progression after an initial response to chemotherapy. Presently, there is no standard of care for such patients. The bone morphogenetic protein 4 (BMP4) has been reported to play a tumor-suppressing role in glioblastoma, but its role in glioblastoma multidrug resistance (MDR) is not clear. We reported that BMP4 can reverse MDR of glioblastoma through the inhibition of B-cell lymphoma 2(BCL-2) and glial cell derived neurotrophic factor (GDNF). We showed that the expression level of BMP4 was lower in glioblastoma compared to normal brain tissue, and also showed that BMP4 expression decreased in multidrug resistance cell line U251/TMZ compared to U251 cells. Our research demonstrated that over-expression of BMP4 can reverse the multidrug resistance. BCL-2 and GDNF were inhibited when BMP4 was over-expressed, and this data were consistent with the negative relationship in human samples; analysis of 40 patient's glioblastoma and brain samples revealed a significant negative correlation between BMP4 and BCL-2, GDNF. When BCL-2 and GDNF were knocked down, the effect of BMP4 in regulating MDR was partially lost. This novel result showed, for the first time, that BMP4 can reverse MDR in glioblastoma, which involved negative inhibition of BCL-2 and GDNF.

Synergistic anti-cancer mechanisms of curcumin and paclitaxel for growth inhibition of human brain tumor stem cells and LN18 and U138MG cells

Glioblastoma, the deadliest brain tumor in humans, responds poorly to conventional chemotherapeutic agents because of existence of highly chemoresistant human brain tumor stem cells (HBTSC). An effective therapeutic strategy is urgently needed to target HBTSC as well as other glioblastoma cells. We explored synergistic efficacy of a low dose of curcumin (CCM) and a low dose of paclitaxel (PTX) in HBTSC and human glioblastoma LN18 (p53 mutant and PTEN proficient) and U138MG (p53 mutant and PTEN mutant) cells. The highest expression of the cancer stem cell markers aldehyde dehydrogenase 1 (ALDH1) and CD133 occurred in HBTSC when compared with LN18 and U138MG cells. Combination of 20μM CCM and 10nM PTX worked synergistically and more effectively than either drug alone in decreasing viability in all cells. Combination of CCM and PTX was highly effective in inducing both morphological and biochemical features of apoptosis. Apoptosis required activation of caspase-8, cleavage of Bid to tBid, increase in Bax:Bcl-2 ratio, and mitochondrial release of cytochrome c, Smac, and apoptosis-inducing factor (AIF). Phosphorylation of Bcl-2 following combination therapy appeared to promote Bax homodimerization and mitochondrial release of pro-apoptotic factors into the cytosol. Increases in activities of cysteine proteases confirmed the completion of apoptotic process. Combination therapy inhibited invasion of cells, reduced expression of survival and proliferation factors and also angiogenic factors, and prevented HBTSC, LN18, and U138MG cells from promoting network formation. Collectively, the combination of CCM and PTX worked as a promising therapy for controlling the growth of HBTSC and other glioblastoma cells.

Survivin knockdown increased anti-cancer effects of (-)-epigallocatechin-3-gallate in human malignant neuroblastoma SK-N-BE2 and SH-SY5Y cells

Neuroblastoma is a solid tumor that mostly occurs in children. Malignant neuroblastomas have poor prognosis because conventional chemotherapeutic agents are hardly effective. Survivin, which is highly expressed in some malignant neuroblastomas, plays a significant role in inhibiting differentiation and apoptosis and promoting cell proliferation, invasion, and angiogenesis. We examined consequences of survivin knockdown by survivin short hairpin RNA (shRNA) plasmid and then treatment with (-)-epigallocatechin-3-gallate (EGCG), a green tea flavonoid, in malignant neuroblastoma cells. Our Western blotting and laser scanning confocal immunofluorescence microscopy showed that survivin was highly expressed in malignant neuroblastoma SK-N-BE2 and SH-SY5Y cell lines and slightly in SK-N-DZ cell line. Expression of survivin was very faint in malignant neuroblastoma IMR32 cell line. We transfected SK-N-BE2 and SH-SY-5Y cells with survivin shRNA, treated with EGCG, and confirmed knockdown of survivin at mRNA and protein levels. Survivin knockdown induced morphological features of neuronal differentiation, as we observed following in situ methylene blue staining. Combination of survivin shRNA and EGCG promoted neuronal differentiation biochemically by increases in the expression of NFP, NSE, and e-cadherin and also decreases in the expression of Notch-1, ID2, hTERT, and PCNA. Our in situ Wright staining and Annexin V-FITC/PI staining showed that combination therapy was highly effective in inducing, respectively, morphological and biochemical features of apoptosis. Apoptosis occurred with activation of caspase-8 and cleavage of Bid to tBid, increase in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and increases in the expression and activity of calpain and caspase-3. Combination therapy decreased migration of cells through matrigel and inhibited proliferative (p-Akt and NF-κB), invasive (MMP-2 and MMP-9), and angiogenic (VEGF and b-FGF) factors. Also, in vitro network formation ability of cells was significantly inhibited by survivin silencing and completely by combination of survivin silencing and EGCG treatment. Collectively, survivin silencing potentiated anti-cancer effects of EGCG in human malignant neuroblastoma cells having survivin overexpression.