Identification and Characterization of Synthetic Viability with ERCC1 Deficiency in Response to Interstrand Crosslinks in Lung Cancer

• Published in: Clinical cancer research 2019-04, Vol.25 (8), p.2523-2536
• Main Authors: Heyza, Joshua R, Lei, Wen, Watza, Donovan, Zhang, Hao, Chen, Wei, Back, Jessica B, Schwartz, Ann G, Bepler, Gerold, Patrick, Steve M
• Format: Article
• Language: English
• Subjects: Cisplatin; DNA Repair; DNA-Binding Proteins - deficiency; Endonucleases - deficiency; Humans; Lung Neoplasms
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-18-3094

ERCC1/XPF is a DNA endonuclease with variable expression in primary tumor specimens, and has been investigated as a predictive biomarker for efficacy of platinum-based chemotherapy. The failure of clinical trials utilizing ERCC1 expression to predict response to platinum-based chemotherapy suggests additional mechanisms underlying the basic biology of ERCC1 in the response to interstrand crosslinks (ICLs) remain unknown. We aimed to characterize a panel of ERCC1 knockout (Δ) cell lines, where we identified a synthetic viable phenotype in response to ICLs with ERCC1 deficiency. We utilized the CRISPR-Cas9 system to create a panel of ERCC1Δ lung cancer cell lines which we characterized. We observe that loss of ERCC1 hypersensitizes cells to cisplatin when wild-type (WT) p53 is retained, whereas there is only modest sensitivity in cell lines that are p53 . In addition, when p53 is disrupted by CRISPR-Cas9 (p53*) in ERCC1Δ/p53 cells, there is reduced apoptosis and increased viability after platinum treatment. These results were recapitulated in 2 patient data sets utilizing p53 mutation analysis and ERCC1 expression to assess overall survival. We also show that kinetics of ICL-repair (ICL-R) differ between ERCC1Δ/p53 and ERCC1Δ/p53* cells. Finally, we provide evidence that cisplatin tolerance in the context of ERCC1 deficiency relies on DNA-PKcs and BRCA1 function. Our findings implicate p53 as a potential confounding variable in clinical assessments of ERCC1 as a platinum biomarker via promoting an environment in which error-prone mechanisms of ICL-R may be able to partially compensate for loss of ERCC1. .