lomeguatrib and Glioblastoma

Treatment resistance of glioblastoma multiforme to chemo- and radiotherapy remains a challenge yet to overcome. In particular, the O. Lomeguatrib, a highly specific MGMT inhibitor, was used to inactivate MGMT protein in vitro. Radiosensitivity of established human glioblastoma multiforme cell lines in combination with lomeguatrib was investigated using the clonogenic survival assay. Inhibition of MGMT was analyzed using Western Blot. Cell cycle distribution and apoptosis were investigated to determine the effects of lomeguatrib alone as well as in combination with ionizing radiation.. Lomeguatrib significantly decreased MGMT protein and reduced radiation-induced G2/M arrest. A radiosensitizing effect of lomeguatrib was observed when administered at 1 µM and increased radioresistance at 20 µM.. Low concentrations of lomeguatrib elicit radiosensitization, while high concentrations mediate a radioprotective effect.

Topics: Apoptosis; Cell Cycle; Cell Line, Tumor; DNA Methylation; DNA Modification Methylases; DNA Repair Enzymes; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; G2 Phase Cell Cycle Checkpoints; Glioblastoma; Humans; Purines; Radiation Tolerance; Tumor Suppressor Proteins

In glioblastoma, the benefit from temozolomide chemotherapy is largely limited to a subgroup of patients (30-35%) with tumors exhibiting methylation of the promoter region of the O

Topics: Animals; Antineoplastic Agents, Alkylating; Brain Neoplasms; Cell Line, Tumor; Dacarbazine; Drug Delivery Systems; Enzyme Inhibitors; Glioblastoma; Guanine; Liposomes; Magnetic Resonance Imaging; Mice; O(6)-Methylguanine-DNA Methyltransferase; Ultrasonic Waves

Glioblastoma multiforme (GBM) is the most common form of malignant glioma. Current therapeutic approach to treat this malignancy involves a combination of surgery, radiotherapy and chemotherapy with temozolomide. Numerous mechanisms contributing to inherent and acquired resistance to this chemotherapeutic agent have been identified and can lead to treatment failure. This study undertook a metabolomics-based approach to characterize the metabolic profiles observed in temozolomide-sensitive and temozolomide-resistant GBM cell lines as well as in a small sub-set of primary GBM tumors. This approach was also utilized to explore the metabolic changes modulated upon cell treatment with temozolomide and lomeguatrib, an MGMT inhibitor with temozolomide-sensitizing potential. Metabolites previously explored for their potential role in chemoresistance including glucose, citrate and isocitrate demonstrated elevated levels in temozolomide-resistant GBM cells. In addition, a signature of metabolites comprising alanine, choline, creatine and phosphorylcholine was identified as up-regulated in sensitive GBM cell line across different treatments. These results present the metabolic profiles associated with temozolomide response in selected GBM models and propose interesting leads that could be leveraged for the development of therapeutic or diagnostic tools to impact temozolomide response in GBMs.

Topics: Antineoplastic Agents, Alkylating; Antineoplastic Combined Chemotherapy Protocols; Brain Neoplasms; Cell Line, Tumor; Dacarbazine; DNA Modification Methylases; DNA Repair Enzymes; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Electrophoresis, Gel, Two-Dimensional; Glioblastoma; Humans; Magnetic Resonance Spectroscopy; Metabolomics; Purines; Temozolomide; Tritium; Tumor Suppressor Proteins

Temozolomide (TMZ) is commonly used in the treatment of glioblastoma (GBM). The MGMT repair enzyme (O (6)-methylguanine-DNA methyltransferase) is an important factor causing chemotherapeutic resistance. MGMT prevents the formation of toxic effects of alkyl adducts by removing them from the DNA. Therefore, MGMT inhibition is an interesting therapeutic approach to circumvent TMZ resistance. The aim of the study was to investigate the effect of the combination of lomeguatrib (an MGMT inactivator) with TMZ, on MGMT expression and methylation. Primary cell cultures were obtained from GBM tumor tissues. The sensitivity of primary GBM cell cultures and GBM cell lines to TMZ, and to the combination of TMZ and lomeguatrib, was determined by a cytotoxicity assay (MTT). MGMT and p53 expression, and MGMT methylation were investigated after drug application. In addition, the proportion of apoptotic cells and DNA fragmentation was analyzed. The combination of TMZ and lomeguatrib in primary GBM cell cultures and glioma cell lines decreased MGMT expression, increased p53 expression, and did not change MGMT methylation. Moreover, apoptosis was induced and DNA fragmentation was increased in cells. In addition, we also showed that lomeguatrib-TMZ combination did not have any effect on the cell cycle. Finally, we determined that the sensitivity of each primary GBM cells and glioma cell lines to the lomeguatrib-TMZ combination was different and significantly associated with the structure of MGMT methylation. Our study suggests that lomeguatrib can be used with TMZ for GBM treatment, although further clinical studies will be needed so as to determine the feasibility of this therapeutic approach.

Topics: Antineoplastic Agents, Alkylating; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Blotting, Western; Brain Neoplasms; Cell Cycle; Cell Proliferation; Comet Assay; Dacarbazine; DNA Methylation; DNA Modification Methylases; DNA Repair Enzymes; DNA, Neoplasm; Female; Flow Cytometry; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; Immunoenzyme Techniques; Male; Middle Aged; Polymerase Chain Reaction; Promoter Regions, Genetic; Purines; Temozolomide; Tumor Cells, Cultured; Tumor Suppressor Proteins