Role of translesion synthesis in cisplatin and temozolomide resistance in Glioma cells

Abstract

Glioma is a Cancer that affects glial cells in the brain. Frequently, it presents poor prognosis, since relapse is usually certain and the protocols of therapy generally induce resistance to treatment. Therapy resistance may be acquired or intrinsic. Therefore, it is necessary to study the mechanisms involved in this process in order to improve the treatment of these patients and increase their survival. Chemotherapy, such as cisplatin or temozolomide (TMZ), for example, induces lesions in the DNA to kill tumor cells. On the other hand, translesion synthesis polymerases (TLS) are enzymes capable of replicating the damaged DNA, without removing the lesions. This mechanism is used by tumor cells to survive the lesions caused by chemotherapy, and, therefore, is a mechanism of resistance to treatments. Moreover, this process is subject to error and can lead to mutagenesis and increase the resistance potential of tumor cells. Little is known about the role of TLS polymerases in TMZ treatment. Preliminar results obtained by Dr. Clarissa R R Rocha in our group identified a list of genes associated with resistance to TMZ in Glioma cell line, using a library of genes activated or knocked out by the CRISPR-Cas9 system. Among these genes, we highlight the participation of some TLS polymerases, such as Pol iota and Pol kappa. Thus, our aim is to validate the data obtained in this initial screening in order to understand the role of TLS polymerases, especially Pol eta, Pol iota and Pol kappa, in cisplatin and TMZ resistance, chemotherapeutic agents used in Glioma therapeutic protocols. For this study, we intend to activate or knock out the genes that encode these TLS in Glioma lines, and observe cell survival, cell cycle and induction of cells in the sub-G1 phase, to analyze the genotoxicity stress caused by these alterations and to observe the replication of the lesion. Thus, this project aims unravel the mechanism of resistance promoted by the TLS polymerases and, in this way, seek new targets that can break resistance to chemotherapy that is already used in clinical treatment for Glioma, in order to contribute to improve the prognosis of patients with this type of Neoplasia. (AU)