New perspective on DNA response pathway (DDR) in glioblastoma, focus on classic biomarkers and emerging roles of ncRNAs.

Abstract

Background: Glioblastoma (GBM) is the most frequent type of primary brain cancer, having a median survival of only 15 months. The current standard of care includes a combination of surgery, radiotherapy (RT) and chemotherapy with temozolomide, but with limited results. Moreover, multiple studies have shown that tumour relapse and resistance to classic therapeutic approaches are common events that occur in the majority of patients, and eventually leading to death. New approaches to better understand the intricated tumour biology involved in GBM are needed in order to develop personalised treatment approaches. Advances in cancer biology have widen our understanding over the GBM genome and allowing a better classification of these tumours based on their molecular profile.

Methods: A new targeted therapeutic approach that is currently investigated in multiple clinical trials in GBM is represented by molecules that target various defects in the DNA damage repair (DDR) pathway, a mechanism activated by endogenous and exogenous factors that induce alteration of DNA, and is involved for the development of chemotherapy and RT resistance. This intricate pathway is regulated by p53, two important kinases ATR and ATM and non-coding RNAs including microRNAs, long-non-coding RNAs and circular RNAs that regulate the expression of all the proteins involved in the pathway.

Results: Currently, the most studied DDR inhibitors are represented by PARP inhibitors (PARPi) with important results in ovarian and breast cancer. PARPi are a class of tumour agnostic drugs that showed their efficacy also in other localisations such as colon and prostate tumours that have a molecular signature associated with genomic instability. These inhibitors induce the accumulation of intracellular DNA damage, cell cycle arrest, mitotic catastrophe and apoptosis.

Conclusions: This study aims to provide an integrated image of the DDR pathway in glioblastoma under physiological and treatment pressure with a focus of the regulatory roles of ncRNAs. The DDR inhibitors are emerging as an important new therapeutic approach for tumours with genomic instability and alterations in DDR pathways. The first clinical trials with PARPi in GBM are currently ongoing and will be presented in the article. Moreover, we consider that by incorporating the regulatory network in the DDR pathway in GBM we can fill the missing gaps that limited previous attempts to effectively target it in brain tumours. An overview of the importance of ncRNAs in GBM and DDR physiology and how they are interconnected is presented.