80P - XRCC6BP1: A key DNA repair gene in platinum-resistant NSCLC

Date 15 April 2016
Event European Lung Cancer Conference 2016 (ELCC) 2016
Session Poster lunch
Topics Thoracic malignancies
Translational Research
Basic Principles in the Management and Treatment (of cancer)
Presenter Martin Barr
Citation Journal of Thoracic Oncology (2016) 11 (supplement 4): S57-S166. S1556-0864(16)X0004-4
Authors M.P. Barr1, E. Foley1, Y. He1, V. Young2, R. Ryan2, S. Nicholson3, N. Leonard3, K. O'Byrne4, S. Cuffe1, S. Finn3
  • 1Thoracic Oncology, St James's Hospital, D8 - Dublin/IE
  • 2Cardiothoracic Surgery, St James's Hospital, D8 - Dublin/IE
  • 3Histopathology, St James's Hospital, D8 - Dublin/IE
  • 4Cancer & Ageing Research Program, Queensland University of Technology, 4102 - Brisbane/AU

Abstract

Background

In the absence of specific treatable mutations, platinum-based doublet chemotherapy remains the gold standard treatment for NSCLC patients. However, its clinical efficacy is hindered in many patients due to both intrinsic and acquired resistance to these agents, in particular, cisplatin. Alterations in the DNA repair capacity of damaged cells is now recognised as an important factor in mediating this phenomenon.

Methods

DNA Repair Pathway RT2 Profiler Arrays were used to elucidate key DNA repair genes in H460 cisplatin resistant (CisR) and corresponding parental (PT) NSCLC cell lines previously generated in our laboratory. DNA repair genes significantly altered in CisR cells were validated using RT-PCR and western blot analysis, respectively. Loss of function studies were carried out using siRNA technology. The effect of gene knockdown on apoptosis was assessed by Annexin V/propidium iodide (PI) staining using the Cytell® Imaging System. DNA damage and repair in response to cisplatin following gene knockdown was investigated using the γH2AX foci formation assay. The translational relevance of these genes was examined in a cohort of chemo-naïve matched normal and tumour lung tissues (n = 20).

Results

We identified a number of important DNA repair genes differentially regulated between H460 PT and CisR NSCLC cells. These included XRCC6BP1, TOP3A, XPA, PMS1 and hSSB1. XRCC6BP1 mRNA was significantly increased (19.4-fold) in H460 CisR cells relative to their PT counterparts. Gene silencing of XRCC6BP1 re-sensitized CisR lung cancer cells to the pro-apoptotic effects of cisplatin and significantly reduced the DNA repair capacity of these cells. Relative to matched normal lung tissues, XRCC6BP1 mRNA was significantly increased in adenocarcinoma tissues (AD), while hSSB1 mRNA was significantly increased in both AD and squamous cell carcinoma (SCC) tissues.

Conclusions

We have identified XRCC6BP1, in addition to hSSB1, as key DNA repair genes implicated in cisplatin resistant NSCLC. Our data highlights the potential of targeting XRCC6BP1, at least in part, in re-sensitizing chemoresistant lung cancer cells to the cytotoxic effects of cisplatin chemotherapy.

Clinical trial identification

Legal entity responsible for the study

St James's Hospital, Dublin

Funding

St James's Hospital, Dublin

Disclosure

All authors have declared no conflicts of interest.