RESUMO
The DNA damage checkpoints provide an anti-cancer barrier in diverse tumour types, however this concept has remained unexplored in prostate cancer (CaP). Furthermore, targeting DNA repair defects by PARP1 inhibitors (PARPi) as a cancer treatment strategy is emerging yet requires suitable predictive biomarkers. To address these issues, we performed immunohistochemical analysis of multiple markers of DNA damage signalling, oxidative stress, DNA repair and cell cycle control pathways during progression of human prostate disease from benign hyperplasia, through intraepithelial neoplasia to CaP, complemented by genetic analyses of TMPRSS2-ERG rearrangement and NQO1, an anti-oxidant factor and p53 protector. The DNA damage checkpoint barrier (γH2AX, pATM, p53) mechanism was activated during CaP tumorigenesis, albeit less and with delayed culmination compared to other cancers, possibly reflecting lower replication stress (slow proliferation despite cases of Rb loss and cyclin D1 overexpression) and progressive loss of ATM activator NKX3.1. Oxidative stress (8-oxoguanine lesions) and NQO1 increased during disease progression. NQO1 genotypes of 390 men did not indicate predisposition to CaP, yet loss of NQO1 in CaP suggested potential progression-opposing tumour suppressor role. TMPRSS2-ERG rearrangement and PTEN loss, events sensitizing to PARPi, occurred frequently along with heterogeneous loss of DNA repair factors 53BP1, JMJD1C and Rev7 (all studied here for the first time in CaP) whose defects may cause resistance to PARPi. Overall, our results reveal an unorthodox DNA damage checkpoint barrier scenario in CaP tumorigenesis, and provide novel insights into oxidative stress and DNA repair, with implications for biomarker guidance of future targeted therapy of CaP.
Assuntos
Dano ao DNA , Estresse Oxidativo , Próstata/patologia , Neoplasias da Próstata/patologia , Idoso , Idoso de 80 Anos ou mais , Reparo do DNA , Progressão da Doença , Regulação Neoplásica da Expressão Gênica , Genótipo , Humanos , Masculino , Pessoa de Meia-Idade , NAD(P)H Desidrogenase (Quinona)/análise , NAD(P)H Desidrogenase (Quinona)/genética , Proteínas de Fusão Oncogênica/análise , Proteínas de Fusão Oncogênica/genética , PTEN Fosfo-Hidrolase/análise , PTEN Fosfo-Hidrolase/genética , Próstata/metabolismo , Neoplasias da Próstata/genética , Neoplasias da Próstata/metabolismoRESUMO
BACKGROUND: The TMPRSS2-ERG gene fusion is one of the most widely spread chromosomal rearrangements in carcinomas. Since its discovery, a number of studies have examined its diagnostic, prognostic and therapeutic implications for prostate cancer where suitable biomarkers are still lacking. The publication data are inconsistent. The aim of this review was to critically evaluate the current clinical impact of this gene fusion. METHODS: The PubMed online database was used to search relevant reviews and original articles. RESULTS: Although the TMPRSS2-ERG gene fusion appears to be a suitable diagnostic biomarker, the prognostic implications of this gene fusion are still unclear. Several new strategies for therapeutically targeting ETS fusions and their modulators have been identified and are currently being investigated. CONCLUSION: Due to the heterogeneity of prostate cancer, the combination of several biomarkers is necessary to accurately assess the presence of prostate cancer, predict its potential clinical outcome and decide on appropriate therapy (e.g. PARP inhibitors).