BACKGROUND: Temozolomide (TMZ) resistance is a significant challenge in treating glioblastoma (GBM). Collagen remodeling has been shown to be a critical factor for therapy resistance in other cancers. This study aimed to investigate the mechanism of TMZ chemoresistance by GBM cells reprogramming collagens. METHODS: Key extracellular matrix components, including collagens, were examined in paired primary and recurrent GBM samples as well as in TMZ-treated spontaneous and grafted GBM murine models. Human GBM cell lines (U251, TS667) and mouse primary GBM cells were used for in vitro studies. RNA-sequencing analysis, chromatin immunoprecipitation, immunoprecipitation-mass spectrometry, and co-immunoprecipitation assays were conducted to explore the mechanisms involved in collagen accumulation. A series of in vitro and in vivo experiments were designed to assess the role of the collagen regulators prolyl 4-hydroxylase subunit alpha 1 (P4HA1) and yes-associated protein (YAP) in sensitizing GBM cells to TMZ. RESULTS: This study revealed that TMZ exposure significantly elevated collagen type I (COL I) expression in both GBM patients and murine models. Collagen accumulation sustained GBM cell survival under TMZ-induced stress, contributing to enhanced TMZ resistance. Mechanistically, P4HA1 directly binded to and hydroxylated YAP, preventing ubiquitination-mediated YAP degradation. Stabilized YAP robustly drove collagen type I alpha 1 ( COL1A1) transcription, leading to increased collagen deposition. Disruption of the P4HA1-YAP axis effectively reduced COL I deposition, sensitized GBM cells to TMZ, and significantly improved mouse survival. CONCLUSION P4HA1 maintained YAP-mediated COL1A1 transcription, leading to collagen accumulation and promoting chemoresistance in GBM.
Temozolomide ; Humans ; Glioblastoma/drug therapy* ; Animals ; Mice ; Cell Line, Tumor ; Drug Resistance, Neoplasm/genetics* ; YAP-Signaling Proteins ; Hydroxylation ; Dacarbazine/pharmacology* ; Adaptor Proteins, Signal Transducing/metabolism* ; Transcription Factors/metabolism* ; Collagen/biosynthesis* ; Collagen Type I/metabolism* ; Prolyl Hydroxylases/metabolism* ; Antineoplastic Agents, Alkylating/therapeutic use*

In gliomas, the canonical Wingless/Int (WNT)/β-catenin pathway is increased while peroxisome proliferator-activated receptor gamma (PPAR-γ) is downregulated. The two systems act in an opposite manner. This review focuses on the interplay between WNT/β-catenin signaling and PPAR-γ and their metabolic implications as potential therapeutic target in gliomas. Activation of the WNT/β-catenin pathway stimulates the transcription of genes involved in proliferation, invasion, nucleotide synthesis, tumor growth, and angiogenesis. Activation of PPAR-γ agonists inhibits various signaling pathways such as the JAK/STAT, WNT/β-catenin, and PI3K/Akt pathways, which reduces tumor growth, cell proliferation, cell invasiveness, and angiogenesis. Nonsteroidal anti-inflammatory drugs, curcumin, antipsychotic drugs, adiponectin, and sulforaphane downregulate the WNT/β-catenin pathway through the upregulation of PPAR-γ and thus appear to provide an interesting therapeutic approach for gliomas. Temozolomide (TMZ) is an antiangiogenic agent. The downstream action of this opposite interplay may explain the TMZ-resistance often reported in gliomas.
Animals ; Brain Neoplasms ; metabolism ; therapy ; Dacarbazine ; analogs & derivatives ; pharmacology ; Down-Regulation ; drug effects ; Glioma ; metabolism ; therapy ; Humans ; PPAR gamma ; metabolism ; Temozolomide ; Wnt Signaling Pathway ; drug effects ; physiology

OBJECTIVETo observe the effect of RITA, a small molecule that targets p53, combined with temozolomide (TMZ) on proliferation, colony formation and apoptosis of human glioblastoma U87 cells and explore the underlying mechanism.

METHODSCultured U87 cells were treated with RITA (1, 5, 10, 20 µmol/L), TMZ, or RITA+TMZ (half dose) for 24, 48 or 72 h. MTS assay were used to detect the cell proliferation, and the cell proliferation rate and inhibitory rate were calculated. The effect of combined treatments was evaluated by the q value. The expressions of p53, p21 and other apoptosis-associated genes were detected by qRT-PCR and Western blotting; cell apoptosis was assayed using flow cytometry with Annexin V/PI double staining; colony formation of the cells was detected with crystal violet staining.

RESULTSMTS assay showed that RITA at the 4 doses more potently inhibited U87 cell viability than TMZ at 72 h (P=0.000) with inhibitory rates of 25.94%-41.38% and 3.84%-8.20%, respectively. RITA combined with TMZ caused a more significant inhibition of U87 cells (29.21%-52.11%) than RITA (P<0.01) and TMZ (P=0.000) alone. At the doses above 5 µmol/L, the combined treatments with RITA+TMZ for 48 h resulted in q values exceeding 1.2 and showed an obvious synergistic effect of the drugs. Both RITA and TMZ, especially the latter, significantly increased the expressions of p53, p21, puma, and other apoptosis-associated genes to accelerate apoptosis and inhibit the growth and colony formation of U87 cells, and the effect was more obvious with a combined treatment.

CONCLUSIONRITA inhibits the growth of human glioblastoma cells and enhance their sensitivity to TMZ by up-regulating p53 expression, and when combined, RITA and TMZ show a synergistic effect to cause a stronger cell inhibition.

Apoptosis ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cell Survival ; Dacarbazine ; analogs & derivatives ; pharmacology ; Furans ; pharmacology ; Glioblastoma ; drug therapy ; Humans

Although methyltransferase has been recognized as a major element that governs the epigenetic regulation of the genome during temozolomide (TMZ) chemotherapy in glioblastoma multiforme (GBM) patients, its regulatory effect on glioblastoma chemoresistance has not been well defined. This study investigated whether DNA methyltransferase (DNMT) expression was associated with TMZ sensitivity in glioma cells and elucidated the underlying mechanism. DNMT expression was analyzed by western blotting. miR-20a promoter methylation was evaluated by methylation-specific PCR. Cell viability and apoptosis were assessed using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and TdT-mediated dUTP-biotin nick end labeling assays, respectively. The results showed that compared with parental U251 cells, DNMT1 expression was downregulated, miR-20a promoter methylation was attenuated and miR-20a levels were elevated in TMZ-resistant U251 cells. Methyltransferase inhibition by 5-aza-2\'-deoxycytidine treatment reduced TMZ sensitivity in U251 cells. In U251/TM cells, DNMT1 expression was negatively correlated with miR-20a expression and positively correlated with TMZ sensitivity and leucine-rich repeats and immunoglobulin-like domains 1 expression; these effects were reversed by changes in miR-20a expression. DNMT1 overexpression induced an increase in U251/TM cell apoptosis that was inhibited by the miR-20a mimic, whereas DNMT1 silencing attenuated U251/TM cell apoptosis in a manner that was abrogated by miR-20a inhibitor treatment. Tumor growth of the U251/TM xenograft was inhibited by pcDNA-DNMT1 pretreatment and boosted by DNMT1-small hairpin RNA pretreatment. In summary, DNMT1 mediated chemosensitivity by reducing methylation of the microRNA-20a promoter in glioma cells.
Animals ; Antineoplastic Agents, Alkylating/*pharmacology/therapeutic use ; Apoptosis/drug effects ; Brain/drug effects/metabolism/pathology ; Brain Neoplasms/drug therapy/*genetics/pathology ; DNA (Cytosine-5-)-Methyltransferase/antagonists & inhibitors/*genetics/metabolism ; DNA Methylation ; Dacarbazine/*analogs & derivatives/pharmacology/therapeutic use ; Drug Resistance, Neoplasm ; Female ; Gene Expression Regulation, Neoplastic ; Glioma/drug therapy/*genetics/pathology ; Humans ; Mice, Inbred C57BL ; MicroRNAs/*genetics ; Promoter Regions, Genetic

OBJECTIVETo investigate programmed cell death induced by temozolomide in rat glioma C6 cell line.

METHODSRat glioma C6 cell line was treated by temozolomide at different concentrations and for different time lengths. MTT assay was used to evaluate the cell inhibition rate to determine the optimal exposure time and concentration. After the exposure to 400 µg/ml temozolomide for 24 h, the cells were observed for programmed cell death using HE staining, Hochest and Tunnel assay, Western blotting, and immunohistochemistry.

RESULTSMTT, HE staining, and Hochest and Tunnel assay all showed temozolomide-induced apoptosis in rat glioma C6 cell line. Western blotting and immunohistochemistry revealed up-regulation of Bax and down-regulation of Bcl-2 expression in the exposed cells, where the expressions of caspases 3, 8, 9, and 12 remained unchanged.

CONCLUSIONTemozolomide induces apoptosis in rat glioma C6 cell line through a caspase- independent pathway.

Animals ; Apoptosis ; Caspases ; Cell Line, Tumor ; Dacarbazine ; analogs & derivatives ; pharmacology ; Down-Regulation ; Glioma ; pathology ; Rats ; Up-Regulation

O6-methylguanine DNA methyltransferase (MGMT) can remove DNA alkylation adducts, thereby repairing damaged DNA and contributing to the drug resistance of gliomas to alkylating agents. In addition, glioma stem-like cells (GSCs) have been demonstrated to be involved in the recurrence and treatment resistance of gliomas. In this study, we aimed to investigate MGMT expression and regulatory mechanisms in GSCs and the association of MGMT with temozolomide (TMZ) sensitivity. GSCs were enriched from one MGMT-positive cell line (SF-767) and 7 MGMT-negative cell lines (U251, SKMG-4, SKMG-1, SF295, U87, MGR1, and MGR2) through serum-free clone culture. GSCs from the U251G, SKMG-4G, SF295G, and SKMG-1G cell lines became MGMT-positive, but those from the U87G, MGR1G, and MGR2G cell lines remained MGMT-negative. However, all the GSCs and their parental glioma cell lines were positive for nuclear factor-κB (NF-κB). In addition, GSCs were more resistant to TMZ than their parental glioma cell lines (P < 0.05). However, there was no significant difference in the 50% inhibition concentration (IC50) of TMZ between MGMT-positive and MGMT-negative GSCs (P > 0.05). When we treated the MGMT-positive GSCs with TMZ plus MG-132 (an NF-κB inhibitor), the antitumor activity was significantly enhanced compared to that of GSCs treated with TMZ alone (P <0.05). Furthermore, we found that MGMT expression decreased through the down-regulation of NF-κB expression by MG-132. Our results show that MG-132 may inhibit NF-κB expression and further decrease MGMT expression, resulting in a synergistic effect on MGMT-positive GSCs. These results indicate that enhanced MGMT expression contributes to TMZ resistance in MGMT-positive GSCs.
Antineoplastic Agents, Alkylating ; pharmacology ; Cell Line, Tumor ; Dacarbazine ; analogs & derivatives ; pharmacology ; Drug Resistance, Neoplasm ; Drug Synergism ; Glioma ; metabolism ; pathology ; Humans ; Leupeptins ; pharmacology ; NF-kappa B ; antagonists & inhibitors ; metabolism ; Neoplastic Stem Cells ; metabolism ; O(6)-Methylguanine-DNA Methyltransferase ; metabolism

OBJECTIVETo investigate the new mechanism of temozolomide (TMZ) induced anti-tumor effects on glioblastoma cells in vitro.

METHODSGrade IV glioma cell lines SHG44 and U251 cells were treated with TMZ. MTT test was used to determine the proliferation of glioma cells. Hoechst 33342 assay was used to detect apoptosis in the tumor cells. The cell cycle progression was assessed by flow cytometry. The level of intracellular reactive oxygen species (ROS) was detected using DCFH-DA probe. real-time PCR assay and Western blotting were used to analyze the expression of SIRT1.

RESULTSTreatment with TMZ for 72 hours inhibited cell proliferation (P < 0.05) and induced apoptosis in the two cell lines in a concentration-dependent manner. TMZ at 100 µmol/L significantly resulted in G(2)/M cell cycle arrest (66.16%, 69.65%), and triggered a robust increase in cell apoptosis [(33.4 ± 1.8)% and (26.8 ± 3.2)%]. TMZ remarkably increased reactive oxygen species (ROS) production (P < 0.05), indicating an overexpression of signal for SIRT1 activation.

CONCLUSIONSOur findings suggest that temozolomide mediates anti-tumor effects on glioma cells in vitro via ROS-dependent SIRT1 signaling pathway, therefore, provide a theoretical evidence for a new approach to improve the treatment of glioma in future.

Antineoplastic Agents, Alkylating ; administration & dosage ; pharmacology ; Apoptosis ; drug effects ; Cell Cycle ; drug effects ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Dacarbazine ; administration & dosage ; analogs & derivatives ; pharmacology ; Dose-Response Relationship, Drug ; Glioblastoma ; pathology ; Humans ; Reactive Oxygen Species ; metabolism ; Signal Transduction ; drug effects ; Sirtuin 1 ; metabolism

BACKGROUNDTreatment for malignant glioma generally consists of cytoreductive surgery followed by radiotherapy and chemotherapy. In this study, we intended to investigate the effects of 2-propylpentanoic acid (VPA), a histone deacetylase inhibitor, on chemosensitivity and radiosensitivity in human glioma cell lines.

METHODSHuman glioma cell lines, T98-G, and SF295, were treated with temozolomide (TMZ) or irradiation (IR), with or without VPA (1.0 mmol/L). Then, cytotoxicity and clonogenic survival assay was performed. Cell cycle stage, apoptosis, and autophagy were also detected using flow cytometry and dansyl monocadaverin (MDC) incorporation assay. One-way analysis of variance (ANOVA) and t-test were used to analyze the differences among variant groups.

RESULTSMild cytotoxicity of VPA was revealed in both cell lines, T98-G and SF295, with the 50% inhibiting concentration (IC50) value of (3.85 ± 0.58) mmol/L and (2.15 ± 0.38) mmol/L, respectively; while the IC50 value of TMZ was (0.20 ± 0.09) mmol/L for T98-G and (0.08 ± 0.02) mmol/L for SF295. Moreover, if combined with VPA (1.0 mmol/L) for 96 hours, the sensitivity of glioma cells to TMZ was significant increased (P < 0.05). The surviving fractions at 2 Gy (SF2) of T98-G and SF295 cells exposed to IR alone were 0.52 and 0.58. However, when VPA was combined with IR, the SF2 of T98-G and SF295 dropped to 0.39 (P = 0.047) and 0.49 (P = 0.049), respectively. Treatment with VPA plus TMZ or IR also resulted in a significant decrease in the proportion of cells in the G2 phase and increased apoptotic rates as well as autophagy in T98-G and SF295 cell lines (P < 0.01).

CONCLUSIONVPA may enhance the activities of TMZ and IR on glioma cells possibly through cell cycle block and promote autophagy, and thus could be a potential sensitizer of glioma treatment.

Apoptosis ; drug effects ; radiation effects ; Blotting, Western ; Cell Line, Tumor ; Cell Survival ; drug effects ; radiation effects ; Dacarbazine ; analogs & derivatives ; pharmacology ; Flow Cytometry ; Glioma ; metabolism ; Histone Deacetylase Inhibitors ; pharmacology ; Humans ; Valproic Acid ; pharmacology

Antineoplastic Agents, Alkylating ; pharmacology ; Apoptosis ; drug effects ; Benzimidazoles ; pharmacology ; DNA Repair ; Dacarbazine ; analogs & derivatives ; pharmacology ; Drug Resistance, Neoplasm ; drug effects ; physiology ; Humans ; Membrane Proteins ; metabolism ; O(6)-Methylguanine-DNA Methyltransferase ; antagonists & inhibitors ; metabolism ; Poly(ADP-ribose) Polymerase Inhibitors ; Poly(ADP-ribose) Polymerases ; metabolism ; Proto-Oncogene Proteins ; metabolism ; Purines ; pharmacology ; Pyrimidines ; pharmacology ; Tumor Suppressor Protein p53 ; metabolism

BACKGROUNDGlioma is the most common primary brain tumor with poor prognosis. Temozolomide has been used with thalidomide to treat gliomas. We investigated the synergistic mechanism of these two drugs in vitro.

METHODSHuman malignant glioma cells U251-MG were cultured and assigned to four groups with different treatments for 3 days: temozolomide group (100 micromol/L), thalidomide group (100 microg/L), temozolomide (100 micromol/L) plus thalidomide group (100 microg/L) and control group. MTT assay was applied to evaluate the cell viability. Cell cycle was analyzed by flow cytometry. The ultra-structural features of autophagosomes were observed with electron microscope. Acridine orange and monodansylcadaverine were adopted to label autophagosomes and flow cytometry was applied for quantification of autophagosomes. The expression of autophagy-associated protein was detected by Western blotting.

RESULTSProliferation of tumor cell was obviously suppressed by temozolomide with thalidomide treatment than by either drug used alone (P = 0.000 for each day). The combination treatment induced cell cycle arrest at G0/G1 phase. Typical autophagic ultra-structural character was found after the combined treatment. Thalidomide promoted the autophagy induced by temozolomide. The autophagy-associated proteins-microtubule associated protein 1 light chain 3 (MAP1LC3) and Beclin1 were more significantly up-regulated by the combined treatment than temozolomide used alone (MAP1LC3, P = 0.000; Beclin1, P = 0.004). The expression level of phosphatase and tensin homolog deleted on chromosome ten (PTEN), which promoted autophagy by suppressing PI3K/Akt/mTOR signaling pathway, was elevated by thalidomide (thalidomide group: P = 0.000; combined group: P = 0.002).

CONCLUSIONSThalidomide enhances the cytotoxicity of temozolomide by promoting the autophagy induced by temozolomide. Contributing to the up-regulation of PTEN by thalidomide, the expression of autophagy associated protein-MAP1LC3 and Beclin1 was enhanced, which leads to a reinforced autophagy in the combined treatment of temozolomide and thalidomide in vitro.

Antineoplastic Agents, Alkylating ; pharmacology ; Autophagy ; drug effects ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Dacarbazine ; analogs & derivatives ; pharmacology ; Glioma ; pathology ; Humans ; Thalidomide ; pharmacology