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Siobhan Nicholson



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    MA06 - PDL1, TMB and DNA Repair (ID 903)

    • Event: WCLC 2018
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
    • Moderators:
    • Coordinates: 9/24/2018, 13:30 - 15:00, Room 206 AC
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      MA06.09 - XRCC6BP1: A DNA Repair Gene in Cisplatin Resistant Lung Cancer Stem Cells That May Predict Survival Outcomes in Patients (ID 14024)

      14:30 - 14:35  |  Author(s): Siobhan Nicholson

      • Abstract
      • Presentation
      • Slides

      Background

      Alterations in the DNA repair capacity of damaged cells is now recognised as an important factor in mediating resistance to chemotherapeutic agents.

      a9ded1e5ce5d75814730bb4caaf49419 Method

      DNA Repair Pathway RT2 Profiler Arrays were used to elucidate key DNA repair genes implicated in chemoresistant NSCLC cells using cisplatin resistant (CisR) and corresponding parental (PT) H460 cells. DNA repair genes significantly altered in CisR cells were validated at the mRNA and protein level. The translational relevance of differentially expressed genes was examined in a cohort of chemo-naïve matched normal and tumour lung tissues from NSCLC patients. Loss of function studies were carried out using siRNA technology. The effect of XRCC6BP1 gene knockdown on apoptosis was assessed by FACS. Cellular expression and localisation of XRCC6BP1 protein and γH2AX foci in response to cisplatin were examined by immunofluorescence (Cytell™). To investigate a role for XRCC6BP1 in lung cancer stem cells, Side Population (SP) studies were used to characterise stem-like subpopulations within chemoresistant cells. XRCC6BP1 mRNA analysis was also examined in ALDH1+ and ALDH1- subpopulations. Immunohistochemistry analysis was carried out in resected lung tumour tissues and XRCC6BP1 expression was correlated with survival in addition to a number of clinicopathological parameters such as tumour stage & grade, gender, smoking status and chemotherapy.

      4c3880bb027f159e801041b1021e88e8 Result

      We identified a number of critical DNA repair genes that are differentially regulated between PT and CisR NSCLC cells. XRCC6BP1 mRNA and protein expression was significantly increased H460 CisR cells relative to their PT counterparts. Relative to matched normal lung tissues, XRCC6BP1 mRNA was significantly increased in lung adenocarcinoma patients. Gene silencing of XRCC6BP1 induced significant apoptosis of chemoresistant cells and reduced their DNA repair capacity. Immunofluorescence studies showed an increase in XRCC6BP1 protein expression and gH2AX foci in CisR cells. SP analysis revealed a significantly higher stem cell population in resistant cells, while XRCC6BP1 mRNA expression was considerably increased in SKMES-1, H460 and H1299 CisR cells positive for ALDH1 activity (ALDH1+) compared to ALDH1- cells. IHC scoring of XRCC6BP1 demonstrated poor survival outcomes for NSCLC patients with high expression of this DNA repair gene.

      8eea62084ca7e541d918e823422bd82e Conclusion

      Our data highlight the potential of targeting components of the DNA repair pathway, in particular XRCC6BP1, in chemoresistant lung cancer. Furthermore, XRCC6BP1 may play an important role in subsets of lung cancer stem cells which, at least in part, may be responsible for driving and maintaining the cisplatin resistant phenotype in NSCLC.

      6f8b794f3246b0c1e1780bb4d4d5dc53

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