Glioblastoma (GBM) is the most common and malignant type of glioma. The resistance of these tumors to treatment is a major challenge to be overcome in order to obtain the most successful therapies applied to patients with GBM, whose survival does not exceed 15 months after diagnosis. Thus, it becomes relevant to investigate the mechanisms involved in GBM resistance to anticancer agents. The main goal of new treatment modalities look for the increase of therapeutic efficacy with reduced side effects, and a new emerging strategy based on the inhibition of DNA repair proteins, such as PARP-1, has been considered as a promising molecular target for sensitizing tumor cells to DNA-damaging agents (chemotherapy and radiation). PARP-1 is a protein activated in response to DNA breaks, and participates in DNA repair complexes of several repair pathways, such as Base Excision Repair (BER), Homologous Recombination (HR) and Non-Homologous End-Joining (NHEJ), suggesting a wide variety of functions performed by this enzyme in several processes of DNA repair. Based on the hypothesis that these repair processes represent an important form of therapeutic resistance, the objective of the present study is to test whether a PARP-1 inhibitor (NU1025) associated with temozolomide (TMZ) treatment is capable of increasing the cytotoxic effects of TMZ, ultimately sensitizing the tumor cells. Three GBM cell lines (T98G, LN18, and U87) presenting different degrees of TMZ resistance will be investigated. The effects of the combined treatment (drug + NU1025) will be evaluated by performing several cellular assays (clonogenic survival, cell cycle kinetics, DNA damage induction, death and invasion assays) and molecular analyses (gene and protein expression analysis). Additionally, in order to validate the use of NU1025 agent as a possible GBM therapeutic strategy in combination with TMZ treatment, PARP-1 will be down-regulated by siRNA and several assays will be performed. Based on the literature information, as well as on previous data from our laboratory, this project aims to apply strategies of DNA repair inhibition to sensitize GBM cells to TMZ treatment. We expect that the results obtained may be relevant to clinical practice and may contribute to the development of new therapeutic strategies, which could ultimately increase the survival of patients with GBM.
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