Author of

• 14490

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  P2.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 234)

  • Event: WCLC 2015
  • Type: Poster
  • Track: Biology, Pathology, and Molecular Testing
  • Presentations: 1
  • Moderators:
  • Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)

  • 14538

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    P2.04-048 - Analysis of Gene Expression in the Re-Replication Pathway and Selective Blockade with Checkpoint Inhibitors as a Therapeutic Option in NSCLC (ID 2594)

    09:30 - 09:30  |  Author(s): S. García-Román
    • Abstract
    • Slides

    Background:
    Targeted lung cancer therapy has undoubtedly made a difference to the treatment of EGFR mutation and ALK translocation carriers. However, targeted therapies for other subgroups like squamous cell carcinoma are still scarce. Re-replication of the genome could initiate gene amplification and cause chromosomal translocation and loss, contributing to tumor progression. It has been shown that cell cycle checkpoints and DNA damage response are activated when re-replication is induced. Cell cycle checkpoints, mediated by CHK1 and 2, are essential to prevent re-replication and maintain genomic integrity. Specific CHK1 inhibitors such as LY2603618 have been shown to delay tumor growth when given in combination with pemetrexed in NSCLC xenograft models.
    
    Methods:
    We selected a panel of NSCLC adenocarcinoma and squamous cell carcinoma cell lines representing different genetic backgrounds with TP53, KRAS and EGFR mutations. In addition, six PC9-derived, TKI resistant cell lines were included (PC9-ER, PC9-GR1 to GR5). Expression of genes involved in the re-replication pathway (MDC1, ATR, ATM, CHEK2, Rap80, Cdc1, Cdc6, MYC, SLX4, CHEK1, BRCA1, BRCA2, p53, ORC4, ORC5, ORC6 and GMNN) was analyzed by RT-PCR. All cell lines were treated with CHK1 and a CHK1/2 inhibitors, and the IC50 was determined by the MTT assay
    
    Results:
    We observed different expression levels of key genes involved in the re-replication pathway. Interestingly, a p53 mutated squamous cell line (SK MES1), which has high expression levels of CHK1 and CHK2 (22.31 and 18.66, respectively), showed the lowest IC50 in our study (IC50= 0.024 mM) with a CHK1 selective inhibitor (LY2603618). Also, two EGFR-resistant cell lines, one harbouring the T790M mutation, were highly sensitive to CHK1 inhibition (IC50 of 0.19µM for PC-GR5; 0.40 µM for PC9-GR4). Interestingly, when using a dual CHK1-CHK2, the IC50 is significantly higher in the SK MES1 cell line (84.62 µM vs 0.024 µM) when compared to single CHK1 inhibiton

    Half maximal inhibitory concentrations (IC50s) of CHK1 and CHK1-2 inhibitors

    Cell line	CHK1 (IC50 µM, mean)	CHK1-2 (IC50 µM, mean)
    SK-MES1	0.027	84.62
    A549	0.8	15
    HCC78	1.2	33.4
    H2228	2	0.5
    H3255	8.1	12.6
    H1975	22.6	9.6

    
    
    Conclusion:
    A great advance has been made in targeted therapy for NSCLC during the last 10 years. Nevertheless, few specific therapeutic options exist for squamous cell carcinoma of the lung nowadays. Different expression of genes involved in the re-replication pathway, and the sensitivity of some NSCLC cell lines (such as SK-MES1, a squamous carcinoma cell line) to selective CHK-1 and dual CHK1-CHK2 inhibitors identify this pathway as a possible therapeutic target worthy of further investigation.
    
    

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