Author of

• 18974

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  P3.02 - Biology/Pathology (ID 620)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Biology/Pathology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 23972

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    P3.02-024 - Role of FBXW7 in the Maintenance of Quiescent Cancer Stem Cells Resistant to Gefitinib in EGFR Mutation-Positive Non-Small Cell Lung Cancer (ID 8160)

    09:30 - 09:30  |  Author(s): H. Ihara
    • Abstract

    Background:
    Accumulating evidence indicates that quiescent cancer stem cells (CSCs) are involved in the resistance to gefitinib in non-small cell lung cancer (NSCLC) as non-mutational mechanism. We have previously reported that gefitinib-resistant persisters (GRPs) highly expressed stemness factors and had characteristic features of the CSCs phenotype. Recent studies demonstrate that FBXW7, a type of F-box protein, plays an important role in the maintenance of quiescent CSC by mediating the degradation of c-Myc protein by ubiquination. The aim of this study is to figure out the role of FBXW7 in the resistance to gefitinib in NSCLC with EGFR mutation.
    
    Method:
    NSCLC cell lines, PC9 and HCC827, harboring sensitive-EGFR mutation were exposed to high concentration of gefitinib in order to develop GRPs. We tried to knockdown FBXW7 gene expression, and evaluated their sensitivity to gefitinib and CD133-positive stem cell population in GRPs. We also introduced FUCCI plasmid via lentiviral infection in the cells and then investigated the cell cycle and G0-phase cells in GRPs. Furthermore, we established gefitinib-resistant tumor (GRT) model by injecting PC9 cells into NOG-mice followed by gefitinib administration after tumor growth, and evaluated mRNA and protein expression of quiescence-related markers including FBXW7 in vivo.
    
    Result:
    In vitro, GRPs showed high expression of stem cell marker CD133 and quiescence-related markers including FBXW7 and low expression of c-Myc at protein level. Cell cycle analysis revealed that majority of GRPs existed in G0/G1 phase. Silencing of FBXW7 gene reduced CD133-positive cell population in GRPs. Knockdown of FBXW7 also increased susceptibility of cells to gefitinib, reversed population of G0/G1-arrest cells to G2/S/M cells, and decreased cell number of GRPs. In vivo, GRTs after gefitinib treatment revealed high expression of FBXW7 and low expression of c-Myc.
    
    Conclusion:
    These findings suggest that FBXW7 may play a pivotal role in the maintenance of quiescent CSCs resistant to gefitinib in EGFR mutation-positive NSCLC.