PARP‑1 inhibition sensitizes temozolomide‑treated glioblastoma cell lines and decreases drug resistance independent of MGMT activity and PTEN proficiency. 2020

Ana P Montaldi, and Sarah C G Lima, and Paulo R D V Godoy, and Danilo J Xavier, and Elza T Sakamoto-Hojo
Department of Biology, Faculty of Philosophy, Sciences and Letters at Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, São Paulo 14040‑901, Brazil.

Information on the mechanisms that are associated with tumor resistance has the potential to provide the fundamental basis for novel therapeutic strategies. In glioblastoma (GBM), predictive biomarkers of cellular responses to temozolomide (TMZ) combined with poly‑ADP‑ribose polymerase inhibitor (PARPi) remain largely unidentified. In this context, the influence of MGMT (O6‑methylguanine DNA methyltransferase) and PTEN (phosphatase and tensin homologue deleted on chromosome ten) has been studied in addition to the occurrence of synthetic lethality involving PTEN and PARPi. The present study investigated whether PARP‑1 inhibition by NU1025 may increase the cytotoxicity of TMZ‑induced lesions in GBM cells, and whether these mechanisms can be influenced by MGMT and PTEN status. The impact of PTEN deficiency in repair pathways, and the effects of PARP‑1 inhibition and PTEN silencing, in terms of synthetic lethality, were also assessed. NU1025 combined with TMZ effectively sensitized TMZ‑resistant cells (T98G PTEN‑mutated and LN18 PTEN‑wild‑type) and TMZ‑sensitive cells (U251MG PTEN‑mutated), in contrast to NU1025 alone. However, the sensitizing effects were not observed in U87MG (PTEN‑mutated) cells, suggesting that specific genetic alterations may influence the response to drug treatment. The sensitizing effects occurred independently of MGMT activity, which was evaluated in O6‑BG‑treated cells. PTEN silencing using small interfering (si)RNA did not sensitize PTEN‑proficient cells to TMZ + NU1025, or NU1025 alone, indicating an absence of synthetic lethality. The responses to TMZ + NU1025 involved antiproliferative activity, G2/M arrest, double strand breaks and the induction of apoptosis. Following 20 days of recovery after three consecutive days of TMZ treatment, TMZ‑resistant cells were observed. However, when TMZ was combined with NU1025, the viability of T98G and LN18 cells was extremely decreased, indicating a lethal drug combination. Therefore, independently of MGMT proficiency and PTEN status, TMZ combined with PARPi may be a promising strategy that can be used to overcome TMZ acquired resistance in GBM cells.

UI MeSH Term Description Entries
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D011799 Quinazolines A group of aromatic heterocyclic compounds that contain a bicyclic structure with two fused six-membered aromatic rings, a benzene ring and a pyrimidine ring. Quinazoline
D001932 Brain Neoplasms Neoplasms of the intracranial components of the central nervous system, including the cerebral hemispheres, basal ganglia, hypothalamus, thalamus, brain stem, and cerebellum. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary neoplasms are subdivided into benign and malignant forms. In general, brain tumors may also be classified by age of onset, histologic type, or presenting location in the brain. Brain Cancer,Brain Metastases,Brain Tumors,Cancer of Brain,Malignant Primary Brain Tumors,Neoplasms, Intracranial,Benign Neoplasms, Brain,Brain Neoplasm, Primary,Brain Neoplasms, Benign,Brain Neoplasms, Malignant,Brain Neoplasms, Malignant, Primary,Brain Neoplasms, Primary Malignant,Brain Tumor, Primary,Brain Tumor, Recurrent,Cancer of the Brain,Intracranial Neoplasms,Malignant Neoplasms, Brain,Malignant Primary Brain Neoplasms,Neoplasms, Brain,Neoplasms, Brain, Benign,Neoplasms, Brain, Malignant,Neoplasms, Brain, Primary,Primary Brain Neoplasms,Primary Malignant Brain Neoplasms,Primary Malignant Brain Tumors,Benign Brain Neoplasm,Benign Brain Neoplasms,Benign Neoplasm, Brain,Brain Benign Neoplasm,Brain Benign Neoplasms,Brain Cancers,Brain Malignant Neoplasm,Brain Malignant Neoplasms,Brain Metastase,Brain Neoplasm,Brain Neoplasm, Benign,Brain Neoplasm, Malignant,Brain Neoplasms, Primary,Brain Tumor,Brain Tumors, Recurrent,Cancer, Brain,Intracranial Neoplasm,Malignant Brain Neoplasm,Malignant Brain Neoplasms,Malignant Neoplasm, Brain,Neoplasm, Brain,Neoplasm, Intracranial,Primary Brain Neoplasm,Primary Brain Tumor,Primary Brain Tumors,Recurrent Brain Tumor,Recurrent Brain Tumors,Tumor, Brain
D005909 Glioblastoma A malignant form of astrocytoma histologically characterized by pleomorphism of cells, nuclear atypia, microhemorrhage, and necrosis. They may arise in any region of the central nervous system, with a predilection for the cerebral hemispheres, basal ganglia, and commissural pathways. Clinical presentation most frequently occurs in the fifth or sixth decade of life with focal neurologic signs or seizures. Astrocytoma, Grade IV,Giant Cell Glioblastoma,Glioblastoma Multiforme,Astrocytomas, Grade IV,Giant Cell Glioblastomas,Glioblastoma, Giant Cell,Glioblastomas,Glioblastomas, Giant Cell,Grade IV Astrocytoma,Grade IV Astrocytomas
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000071137 Poly (ADP-Ribose) Polymerase-1 A poly(ADP-ribose) polymerase that contains two ZINC FINGERS in its N-terminal DNA-binding region. It modifies NUCLEAR PROTEINS involved in chromatin architecture and BASE EXCISION REPAIR with POLY ADENOSINE DIPHOSPHATE RIBOSE. NAD+ ADP-ribosyltransferase-1,PARP-1 Protein,PARP1 Protein,Poly (ADP-Ribose) Synthase-1,NAD+ ADP ribosyltransferase 1,PARP 1 Protein
D000077204 Temozolomide A dacarbazine derivative that is used as an alkylating antineoplastic agent for the treatment of MALIGNANT GLIOMA and MALIGNANT MELANOMA. 8-Carbamoyl-3-methylimidazo(5,1-d)-1,2,3,5-tetrazin-4(3H)-one,CCRG 81045,CCRG-81045,M&B 39831,M&B-39831,Methazolastone,NSC 362856,NSC-362856,TMZ-Bioshuttle,TMZA-HE,Temodal,Temodar,Temozolomide Hexyl Ester,CCRG81045,M&B39831,NSC362856,TMZ Bioshuttle
D015254 DNA Modification Methylases Enzymes that are part of the restriction-modification systems. They are responsible for producing a species-characteristic methylation pattern, on either adenine or cytosine residues, in a specific short base sequence in the host cell's own DNA. This methylated sequence will occur many times in the host-cell DNA and remain intact for the lifetime of the cell. Any DNA from another species which gains entry into a living cell and lacks the characteristic methylation pattern will be recognized by the restriction endonucleases of similar specificity and destroyed by cleavage. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. DNA Modification Methyltransferases,Modification Methylases,Methylases, DNA Modification,Methylases, Modification,Methyltransferases, DNA Modification,Modification Methylases, DNA,Modification Methyltransferases, DNA
D017209 Apoptosis A regulated cell death mechanism characterized by distinctive morphologic changes in the nucleus and cytoplasm, including the endonucleolytic cleavage of genomic DNA, at regularly spaced, internucleosomal sites, i.e., DNA FRAGMENTATION. It is genetically programmed and serves as a balance to mitosis in regulating the size of animal tissues and in mediating pathologic processes associated with tumor growth. Apoptosis, Extrinsic Pathway,Apoptosis, Intrinsic Pathway,Caspase-Dependent Apoptosis,Classic Apoptosis,Classical Apoptosis,Programmed Cell Death,Programmed Cell Death, Type I,Apoptoses, Extrinsic Pathway,Apoptoses, Intrinsic Pathway,Apoptosis, Caspase-Dependent,Apoptosis, Classic,Apoptosis, Classical,Caspase Dependent Apoptosis,Cell Death, Programmed,Classic Apoptoses,Extrinsic Pathway Apoptoses,Extrinsic Pathway Apoptosis,Intrinsic Pathway Apoptoses,Intrinsic Pathway Apoptosis
D045643 DNA Repair Enzymes Enzymes that are involved in the reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule, which contained damaged regions. DNA Repair Enzyme,Enzyme, DNA Repair,Enzymes, DNA Repair,Repair Enzyme, DNA,Repair Enzymes, DNA

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