Antiproliferative Activity of Chemically Characterized Propolis from Turkey and Its Mechanisms of Action

The aim of this study was to evaluate the ethanolic extract of propolis originated from northern Turkey for its antiproliferative, apoptotic and cell cycle arrest promoting effects on MCF7, HGC27, A549 cancer cell lines and a healthy cell line (HUVEC) in terms of DNA content, morphological features, expression of cell cycle checkpoint proteins p21, p53, Cyclin D1 and immune checkpoint protein PD‐L1. The extract showed moderate antiproliferative activity against all tested cancer cell lines with IC₅₀ values in the range of 58.6–90.7 μg/mL in MTS assay. Further studies indicated that propolis extract exerted apoptotic effect on cancer cell lines, promoted cell cycle arrest through activation of p21 and resulted in accumulation at G0/G1 phase of cancer cells. Propolis treatment caused increased cell size, according to fluorescent imaging except for MCF7. HPTLC analysis revealed that 3‐O‐methylquercetin, chrysin, caffeic acid, CAPE, galangin and pinocembrin were the main components of the extract. The amounts of caffeic acid and CAPE in the extract were found to be 5.5 and 11.1 mg/g, respectively, by a validated HPLC method. Our study is the first one, revealing effect of propolis on PD‐L1 expression on certain cancer cell lines.     

Chilean propolis: antioxidant activity and antiproliferative action in human tumor cell lines

Propolis, a natural product derived from plant resins collected by honeybees, has been used for thousands of years in traditional medicine all over the world. The composition of the propolis depends upon the vegetation of the area from where it was collected and on the bee species. In this study, we investigated the antioxidant activity of a propolis sample, provided by NATURANDES-CHILE, collected in a temperate region of central Chile. In addition, this natural compound was tested for its antiproliferative capacity on KB (human mouth epidermoid carcinoma cells), Caco-2 (colon adenocarcinoma cells) and DU-145 (androgen-insensitive prostate cancer cells) human tumor cell lines. Results showed that this Chilean propolis sample exhibits interesting biological properties, correlated with its chemical composition and expressed by its capacity to scavenge free radicals and to inhibit tumor cell growth.     

NETRIN-4 Protects Glioblastoma Cells FROM Temozolomide Induced Senescence

Glioblastoma multiforme is the most common primary tumor of the central nervous system. The drug temozolomide (TMZ) prolongs lifespan in many glioblastoma patients. The sensitivity of glioblastoma cells to TMZ is interfered by many factors, such as the expression of O-6-methylguanine-DNA methyltransferase (MGMT) and activation of AKT signaling. We have recently identified the interaction between netrin-4 (NTN4) and integrin beta-4 (ITGB4), which promotes glioblastoma cell proliferation via activating AKT-mTOR signaling pathway. In the current work we have explored the effect of NTN4/ITGB4 interaction on TMZ induced glioblastoma cell senescence. We report here that the suppression of either ITGB4 or NTN4 in glioblastoma cell lines significantly enhances cellular senescence. The sensitivity of GBM cells to TMZ was primarily determined by the expression of MGMT. To omit the effect of MGMT, we concentrated on the cell lines devoid of expression of MGMT. NTN4 partially inhibited TMZ induced cell senescence and rescued AKT from dephosphorylation in U251MG cells, a cell line bearing decent levels of ITGB4. However, addition of exogenous NTN4 displayed no significant effect on TMZ induced senescence rescue or AKT activation in U87MG cells, which expressed ITGB4 at low levels. Furthermore, overexpression of ITGB4 combined with exogenous NTN4 significantly attenuated U87MG cell senescence induced by TMZ. These data suggest that NTN4 protects glioblastoma cells from TMZ induced senescence, probably via rescuing TMZ triggered ITGB4 dependent AKT dephosphorylation. This suggests that interfering the interaction between NTN4 and ITGB4 or concomitant use of the inhibitors of the AKT pathway may improve the therapeutic efficiency of TMZ.     

The interruption of atypical PKC signaling and Temozolomide combination therapy against glioblastoma

Current treatment options of glioblastoma include chemotherapy and limited surgical resection. Temozolomide (TMZ) is the current therapeutic choice for chemotherapy. Still, it has severe limitations due to the development of resistance that occurs by genetic modification and constitutive activation of several cell signaling pathways. Therefore, it is essential to develop combination therapy of TMZ with other novel compounds to prevent the development of chemo-resistance. In this study, we used two inhibitors; ICA, an inhibitor of PKC-ι and ζ-Stat, an inhibitor of PKC-ζ. T98G and U87MG glioblastoma cells were treated with either ICA or ζ-stat or TMZ monotherapies, as well as TMZ were combined with either ICA or ζ-stat for five consecutive days. Our in vitro results exhibited that ICA when combined with TMZ, significantly decreased the viability of cancerous cells compared with untreated or TMZ or ICA monotherapies. Additionally, glioblastoma cells were remarkably undergoing apoptosis against the combination treatment of TMZ and ICA nucleotide compared with untreated control cells, as suggested by our Annexin-V/PI flow cytometric analysis. Moreover, the combination of TMZ and ICA also decreased the invasion of glioblastoma cell lines by acting on FAK/Paxillin pathway, as evidenced by scratch assay, transwell invasion assay, Western blot and immunoprecipitation analysis. Furthermore, our in vivo data presented that the combination of ICA and TMZ also reduced glioblastoma tumor growth and volume in mice. These data suggest that atypical PKCs, particularly PKC-ι might be an important therapeutic target as adjuvant therapy in the treatment of glioblastoma.     

Activation of AMP-activated protein kinase by temozolomide contributes to apoptosis in glioblastoma cells via p53 activation and mTORC1 inhibition

Methylating drugs such as temozolomide (TMZ) are widely used in the treatment of brain tumors including malignant glioblastoma. The mechanism of TMZ-induced glioblastoma cell death and apoptosis, however, is not fully understood. Here, we tested the potential involvement of AMP-activated protein kinase (AMPK) in this process. We found that methylating agents TMZ and N-methyl-N'-nitro-N-nitrosoguanidine induce AMPK activation in primary cultured human glioblastoma and glioblastoma cell lines. TMZ-induced O(6)-methylguanine production is involved in AMPK activation. O(6)-benzylguanine, an O(6)-methylguanine-DNA methyltransferase inhibitor, enhances TMZ-induced O(6)-methylguanine production, leading to enhanced reactive oxygen species production, which serves as an upstream signal for AMPK activation. Activation of AMPK is involved in TMZ-induced glioblastoma cell death and apoptosis. AMPK inhibitor (Compound C) or AMPKα siRNA knockdown inhibits TMZ-induced glioblastoma cell death and apoptosis, whereas AMPK activator 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside enhances it. In further studies, we found that activation of AMPK is involved in TMZ-induced p53 activation and subsequent p21, Noxa, and Bax up-regulation. Activation of AMPK by TMZ also inhibits mTOR complex 1 (mTORC1) signaling and promotes anti-apoptosis protein Bcl-2 down-regulation, which together mediate TMZ-induced pro-cell apoptosis effects. Our study suggests that activation of AMPK by TMZ contributes to glioblastoma cell apoptosis, probably by promoting p53 activation and inhibiting mTORC1 signaling.     

The effect of Azo-dyes on glioblastoma cells in vitro

Despite the multidisciplinary standard treatment of glioblastoma (GB) consisting of maximal surgical resection, followed by radiotherapy (RT) plus concomitant chemotherapy with temozolomide (TMZ), the majority of patients experience tumor progression and almost universal mortality. In recent years, efforts have been made to create new agents for GB treatment, of which azo-dyes proved to be potential candidates, showing antiproliferative effects by inducing apoptosis and by inhibiting different signaling pathways. In this study we evaluated the antiproliferative the effect of six azo-dyes and TMZ on a low passage human GB cell line using MTT assay. We found that all compounds proved antiproliferative properties on GB cells. At equimolar concentrations azo-dyes induced more cytotoxic effect than TMZ. We found that Methyl Orange required the lowest IC₅₀ for 3 days of treatment (26.4684 μM), whilst for 7 days of treatment, two azo dyes proved to have the highest potency: Methyl Orange IC₅₀ = 13.8808 μM and Sudan I IC₅₀ = 12.4829 μM. The highest IC₅₀ was determined for TMZ under both experimental situations. Conclusions: Our research represents a novelty, by offering unique valuable data regarding the azo-dye cyototoxic effects in high grade brain tumors. This study may focus the attention on azo-dye agents that may represent an insufficient exploited source of agents for cancer treatment.     

Zinc and Propolis Reduces Cytotoxicity and Proliferation in Skin Fibroblast Cell Culture: Total Polyphenol Content and Antioxidant Capacity of Propolis

It has been demonstrated that zinc exerts its beneficial influence on skin fibroblasts. Propolis, a complex mixture of plant-derived and bees’ products, was reported to stimulate cicatrization processes in skin and prevent infections. The aim of this study was to find out how zinc and propolis influence human skin fibroblasts in cell culture and to compare the effect of individual compounds to the effect of a mixture of zinc and propolis. In this study, zinc, as zinc aspartate, at a concentration of 16 μM, increased human fibroblasts proliferation in cell culture, whereas propolis at a concentration of 0.01 % (w/v) revealed antiproliferative and cytotoxic action followed by mild cell necrosis. In culture, zinc was effectively transported into fibroblasts, and propolis inhibited the amount of zinc incorporated into the cells. An addition of propolis to the medium caused a decrease in the Zn(II) amount incorporated into fibroblasts. The obtained results also indicate an appreciable antioxidant property of propolis and revealed its potential as a supplement when applied at doses lower than 0.01 % (w/v). In conclusion, the present study showed that zinc had a protective effect on human cultured fibroblasts’ viability, although propolis revealed its antiproliferative action and caused mild necrosis.     

Anti-cariogenic and anti-biofilms activity of Tunisian propolis extract and its potential protective effect against cancer cells proliferation

Propolis is a multifunctional substance used by bees to maintain the safety of their hives. It is worldwide used for its potential therapeutic effects. In this study, Tunisian propolis ethanol extract (EEP) was tested for their anti-cariogenic, anti-biofilms and antiproliferative effects of many cell lines. The Tunisian EEP was evaluated in vitro against 33 oral pathogens including streptococci and enterococci using broth microdilution method. The anti-biofilms activity of EEP was assessed via Crystal Violet staining and MTT assays. The Tunisian EEP antiproliferative effect was evaluated on normal (MRC-5) and cancer cell lines (HT-29, A549, Hep-2, raw 264.7, Vero) by the ability of the cells to metabolically reduce MTT to a formazan dye. Our results revealed that Tunisian EEP possessed excellent protective effects against cariogenic and biofilms activity of oral streptococci. Furthermore, EEP showed a strong antiproliferative potencies against all studied cancer cell lines as judged by IC50 and its value ranges from 15.7 ± 3.4 to 200 ± 22.2 μg mL?1. These results suggest that EEP is able to inhibit cancer cell proliferation, cariogenic bacteria and oral biofilms formation. It could have a promising role in the future medicine and nutrition when used as antibiotic or food additive.     

Propolis cinnamic acid derivatives induce apoptosis through both extrinsic and intrinsic apoptosis signaling pathways and modulate of miRNA expression

Propolis cinnamic acid derivatives have a number of biological activities including anti-oxidant and anti-cancer ones. In this study, we aimed to elucidate the mechanism of the anti-cancer activity of 3 representative propolis cinnamic acid derivatives, i.e., Artepilin C, Baccharin and Drupanin in human colon cancer cell lines. Our study demonstrated that these compounds had a potent apoptosis-inductive effect even on drug-resistant colon cancer cells. Combination treatment of human colon cancer DLD-1 cells with 2 of these compounds, each at its IC₂₀ concentration, induced apoptosis by stimulating both intrinsic and extrinsic apoptosis signaling pathways. Especially, Baccharin plus Drupanin exhibited a synergistic growth-inhibitory effect by strengthening both intrinsic and extrinsic apoptotic signaling transduction through TRAIL/DR4/5 and/or FasL/Fas death-signaling loops and by increasing the expression level of miR-143, resulting in decreased expression levels of the target gene MAPK/Erk5 and its downstream target c-Myc. These data suggest that the supplemental intake of these compounds found in propolis has enormous significance with respect to cancer prevention.     

Effects of temozolomide (TMZ) on the expression and interaction of heat shock proteins (HSPs) and DNA repair proteins in human malignant glioma cells

We previously reported the association of HSPA1A and HSPB1 with high-grade astrocytomas, suggesting that these proteins might be involved in disease outcome and response to treatment. With the aim to better understand the resistance/susceptibility processes associated to temozolomide (TMZ) treatment, the current study was performed in three human malignant glioma cell lines by focusing on several levels: (a) apoptotic index and senescence, (b) DNA damage, and (c) interaction of HSPB1 with players of the DNA damage response. Three human glioma cell lines, Gli36, U87, and DBTRG, were treated with TMZ evaluating cell viability and survival, apoptosis, senescence, and comets (comet assay). The expression of HSPA (HSPA1A and HSPA8), HSPB1, O₆-methylguanine-DNA methyltransferase (MGMT), MLH1, and MSH2 was determined by immunocytochemistry, immunofluorescence, and Western blot. Immunoprecipitation was used to analyze protein interaction. The cell lines exhibited differences in viability, apoptosis, and senescence after TMZ administration. We then focused on Gli36 cells (relatively unstudied) which showed very low recovery capacity following TMZ treatment, and this was related to high DNA damage levels; however, the cells maintained their viability. In these cells, MGMT, MSH2, HSPA, and HSPB1 levels increased significantly after TMZ administration. In addition, MSH2 and HSPB1 proteins appeared co-localized by confocal microscopy. This co-localization increased after TMZ treatment, and in immunoprecipitation analysis, MSH2 and HSPB1 appeared interacting. In contrast, HSPB1 did not interact with MGMT. We show in glioma cells the biological effects of TMZ and how this drug affects the expression levels of heat shock proteins (HSPs), MGMT, MSH2, and MLH1. In Gli36 cells, the results suggest that interactions between HSPB1 and MSH2, including co-nuclear localization, may be important in determining cell sensitivity to TMZ.     

The anticancer activity of propolis

Propolis and its compounds have been the subject of many studies due to their antimicrobial and antiinflammatory activity; however, it is now known that they also possess antitumor properties. This review aims to summarize the results of studies on the mechanism of activity of propolis and its active compounds such as CAPE and chrysin in the apoptotic process, and their influence on the proliferation of cancer cells. Our review shows that propolis and its presented compounds induce apoptosis pathways in cancer cells. The antiproliferative effects of propolis, CAPE or chrysin in cancer cells are the result of the suppression of complexes of cyclins, as well as cell cycle arrest. The results of in vitro and in vivo studies suggest that propolis, CAPE and chrysin may inhibit tumor cell progression and may be useful as potential chemotherapeutic or chemopreventive anticancer drugs.     

Expression of Eukaryotic Initiation Factor 5A and Hypusine Forming Enzymes in Glioblastoma Patient Samples: Implications for New Targeted Therapies

Glioblastomas are highly aggressive brain tumors of adults with poor clinical outcome. Despite a broad range of new and more specific treatment strategies, therapy of glioblastomas remains challenging and tumors relapse in all cases. Recent work demonstrated that the posttranslational hypusine modification of the eukaryotic initiation factor 5A (eIF-5A) is a crucial regulator of cell proliferation, differentiation and an important factor in tumor formation, progression and maintenance. Here we report that eIF-5A as well as the hypusine-forming enzymes deoxyhypusine synthase (DHS) and deoxyhypusine hydroxylase (DOHH) are highly overexpressed in glioblastoma patient samples. Importantly, targeting eIF-5A and its hypusine modification with GC7, a specific DHS-inhibitor, showed a strong antiproliferative effect in glioblastoma cell lines in vitro, while normal human astrocytes were not affected. Furthermore, we identified p53 dependent premature senescence, a permanent cell cycle arrest, as the primary outcome in U87-MG cells after treatment with GC7. Strikingly, combined treatment with clinically relevant alkylating agents and GC7 had an additive antiproliferative effect in glioblastoma cell lines. In addition, stable knockdown of eIF-5A and DHS by short hairpin RNA (shRNA) could mimic the antiproliferative effects of GC7. These findings suggest that pharmacological inhibition of eIF-5A may represent a novel concept to treat glioblastomas and may help to substantially improve the clinical course of this tumor entity.     

多甲氧基黄酮对人胶质母细胞瘤细胞系生物学特性的影响

目的：多甲氧基黄酮（PMFs）因其抗氧化、抗癌、抗炎及抗动脉粥样硬化等多样的生物学活性受到国内外学者的广泛关注,但其在神经胶质瘤治疗中的潜在作用尚未见报道。本研究对多甲氧基黄酮处理人胶质母细胞瘤细胞系对其生物学特性的影响,初步探讨PMFs在神经胶质瘤治疗中的潜在应用。方法：不同浓度（0,20,40,60,80,100μg／mL）的PMFs处理人胶质母细胞瘤细胞系U251不同时间后．分别用Annexinv／PI双染法检测细胞凋亡的变化,MTT法检细胞活力的变化,Transwell小室实验检测细胞侵袭能力的变化。结果：随着多甲氧基黄酮的浓度及处理时间的增加,细胞的增殖明显受到抑制,同时诱导细胞大量凋亡,促使细胞生长停滞于G2／M期;此外,多甲氧基黄酮剂量依赖性的抑制胶质瘤细胞的侵袭。结论：PMFs能剂量和时间依赖性降低人胶质母细胞瘤细胞系U251的,同时显著诱导细胞瘤的凋亡和侵袭能力,提示PMFs可能对神经胶质瘤的高增殖性和侵袭性有一定的抑制作用,因此可能具有成为治疗神经胶质瘤药物的潜在应用价值。     

Electroporation Enhances the Anticancer Effects of Novel Cu(II) and Fe(II) Complexes in Chemotherapy-Resistant Glioblastoma Cancer Cells

Schiff base ligand (L) was obtained by condensation reaction between 4-aminopyrimidin-2(1H)-one (cytosine) with 2-hydroxybenzaldehyde. The synthesized Schiff base was used for complexation with Cu(II) and Fe(II) ions used by a molar (2 : 1 mmol ration) in methanol solvent. The structural features of ligand, Cu(II), and Fe(II) metal complexes were determined by standard spectroscopic methods (FT-IR, elemental analysis, proton and carbon NMR spectra, UV/VIS, and mass spectroscopy, magnetic susceptibility, thermal analysis, and powder X-ray diffraction). The synthesized compounds (Schiff base and its metal complexes) were screened in terms of their anti-proliferative activities in U118 and T98G human glioblastoma cell lines alone or in combination with electroporation (EP). Moreover, the human HDF (human dermal fibroblast) cell lines was used to check the bio-compatibility of the compounds. Anti-proliferative activities of all compounds were ascertained using an MTT assay. The complexes exhibited a good anti-proliferative effect on U118 and T98G glioblastoma cell lines. In addition, these compounds had a negligible cytotoxic effect on the fibroblast HDF cell lines. The use of compounds in combination with EP significantly decreased the IC₅₀ values compared to the use of compounds alone (p<0.05). These results show that newly synthesized Cu(II) and Fe(II) complexes can be developed for use in the treatment of chemotherapy-resistant U118 and T98G glioblastoma cells and that treatment with lower doses can be provided when used in combination with EP.     

JNK信号通路对蜂胶抑制白血病K562细胞增殖的调控作用

目的探讨JNK信号通路对蜂胶抑制K562细胞增殖过程的调控作用。方法体外培养K562细胞,用不同浓度蜂胶、c—Jun氨基末端激酶（c—JanN—terminalkinase,JNK）特异性抑制剂SP600125对白血病K562细胞进行处理,用MTT法检测细胞增殖抑制率,流式细胞术（FCM）检测细胞凋亡率,Western印迹检测JNK下游分子c—Jun以及磷酸化c—Jan（p-c-Jun）的变化。结果蜂胶作用K562细胞后,增殖抑制率、凋亡率显著升高,具有时间和剂量依赖性,并伴随p-c-Jun蛋白水平上调;加入SP600125能下调p-c-Jun的水平,显著提高蜂胶对K562细胞的增殖抑制率和凋亡率。结论JNK信号通路参与了蜂胶抑制K562细胞增殖过程的调控。抑制JNK活性可增强蜂胶对K562细胞的增殖抑制、凋亡诱导作用。     

Inhibition of Casein Kinase II by CX-4945, But Not Yes-associated protein (YAP) by Verteporfin,Enhances the Antitumor Efficacy of Temozolomide in Glioblastoma

Overcoming temozolomide (TMZ) resistance in glioma cancer cells remains a major challenge to the effective treatment of the disease. Increasing TMZ efficacy for patients with glioblastoma (GBM) is urgently needed because TMZ treatment is the standard chemotherapy protocol for adult patients with glioblastoma. O⁶-methylguanine-DNA-methyltransferase (MGMT) overexpression is associated with TMZ resistance, and low MGMT is a positive response marker for TMZ therapy. Here, we used 3 glioma cell lines (SF767, U373, and LN229), which had different levels of TMZ sensitivity. We found TMZ sensitivity is positively correlated with MGMT expression and multidrug-resistance protein ABC subfamily G member 2 (ABCG2) in these cells. CK2-STAT3 signaling and Hippo-YAP signaling are reported to regulate MGMT expression and ABCG2 expression, respectively. We combined CK2 inhibitor CX-4945 and YAP inhibitor verteporfin with TMZ treatment. We found that CX-4945 but not verteporfin can sensitize TMZ-resistant cells SF767 to TMZ and that CX-4945 and TMZ combinational treatment was effective for glioma treatment in mouse models compared with TMZ alone.ImplicationsA combination of CK2 inhibitor with TMZ may improve the therapeutic efficiency of TMZ toward GBM with acquired resistance.     

Anti-tumor activities of luteolin and silibinin in glioblastoma cells: overexpression of miR-7-1-3p augmented luteolin and silibinin to inhibit autophagy and induce apoptosis in glioblastoma in vivo

Glioblastoma is the deadliest brain tumor in humans. High systemic toxicity of conventional chemotherapies prompted the search for natural compounds for controlling glioblastoma. The natural flavonoids luteolin (LUT) and silibinin (SIL) have anti-tumor activities. LUT inhibits autophagy, cell proliferation, metastasis, and angiogenesis and induces apoptosis; while SIL activates caspase-8 cascades to induce apoptosis. However, synergistic anti-tumor effects of LUT and SIL in glioblastoma remain unknown. Overexpression of tumor suppressor microRNA (miR) could enhance the anti-tumor effects of LUT and SIL. Here, we showed that 20 µM LUT and 50 µM SIL worked synergistically for inhibiting growth of two different human glioblastoma U87MG (wild-type p53) and T98G (mutant p53) cell lines and natural combination therapy was more effective than conventional chemotherapy (10 µM BCNU or 100 µM TMZ). Combination of LUT and SIL caused inhibition of growth of glioblastoma cells due to induction of significant amounts of apoptosis and complete inhibition of invasion and migration. Further, combination of LUT and SIL inhibited rapamycin (RAPA)-induced autophagy, a survival mechanism, with suppression of PKCα and promotion of apoptosis through down regulation of iNOS and significant increase in expression of the tumor suppressor miR-7-1-3p in glioblastoma cells. Our in vivo studies confirmed that overexpression of miR-7-1-3p augmented anti-tumor activities of LUT and SIL in RAPA pre-treated both U87MG and T98G tumors. In conclusion, our results clearly demonstrated that overexpression of miR-7-1-3p augmented the anti-tumor activities of LUT and SIL to inhibit autophagy and induce apoptosis for controlling growth of different human glioblastomas in vivo.     

MiR-18a regulates the proliferation,migration and invasion of human glioblastoma cell by targeting neogenin

MiR-17-92 cluster has recently been reported as an oncogene in some tumors. However, the association of miR-18a, an important member of this cluster, with glioblastoma remains unknown. Therefore, this study aims to investigate the expression of miR-18a in glioblastoma and its role in biological behavior of U87 and U251 human glioblastoma cell lines. Quantitative RT-PCR results showed that miR-18a was highly expressed in glioblastoma tissues and U87 and U251 cell lines compared with that in human brain tissues and primary normal human astrocytes, and the expression levels were increased along with the rising pathological grades of glioblastoma. Neogenin was identified as the target gene of miR-18a by dual-luciferase reporter assays. RT-PCR and western blot results showed that its expression levels were decreased along with the rising pathological grades of glioblastoma. Inhibition of miR-18a expression was established by transfecting exogenous miR-18a inhibitor into U87 and U251 cells, and its effects on the biological behavior of glioblastoma cells were studied using CCK-8 assay, transwell assay and flow cytometry. Inhibition of miR-18a expression in U87 and U251 cells significantly up-regulated neogenin, and dramatically suppressed the abilities of cell proliferation, migration and invasion, induced cell cycle arrest and promoted cellular apoptosis. Collectively, these results suggest that miR-18a may regulate biological behavior of human glioblastoma cells by targeting neogenin, and miR-18a can serve as a potential target in the treatment of glioblastoma.     

Lovastatin-induced up-regulation of the BH3-only protein, Bim, and cell death in glioblastoma cells

The mechanism of lovastatin-induced cell death was examined in three established human glioblastoma cell lines; U87, U251, and U138. Changes in potential modifiers of apoptosis, including Bcl-2 family proteins and MAP kinase targets after such lovastatin treatment, were evaluated. Lovastatin (5 microm) treatment causes extensive cell death in two of the cell lines, U87 and U251; but only minimal in a third, U138. Lovastatin-induced death occurs in correlation with significantly increased levels of the BH3-only protein, Bim. The up-regulation of Bim levels was directly associated with an increased incidence of apoptosis. Lovastatin treatment in U87 cells results in activation of targets of three major mitogen-activating protein kinase cascades including Erk1/2, JNK and p38. Changes in levels of Bim, as well as increase phosphorylation of Erk1/2, c-jun, and p38 are all prevented by co-incubation of lovastatin and the isoprenylation metabolite, geranylgeranyl pyrophosphate. Inhibition of the MAP kinase pathways failed to block the increased expression of Bim expression or cell death. Further elucidation of the mechanisms of lovastatin-induced up-regulation of Bim and apoptosis in glioblastoma cells are important in determining a potential role for lovastatin as a chemotherapy agent.