Author of

• 11454

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  P2.01 - Poster Session 2 - Cancer Biology (ID 145)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11457

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    P2.01-003 - Modulation of Cisplatin Activity in NSCLC by KRAS Mutants: Role of Specific Mutations at Codon 12 (ID 2296)

    09:30 - 09:30  |  Author(s): R. Frapolli
    • Abstract

    Background
    Non-small-cell lung cancers (NSCLCs) constitute about 85% of lung cancers and have been associated with a poor prognosis, despite the introduction in clinical practice of targeted therapies. The majority of patients are still treated in first-line with a cisplatin containing doublet. New molecular predictors should be discovered. Our attention has been focused on KRAS. Mutations in the KRAS gene have been found in 17% of NSCLC patients mostly at codon 12. It has been observed that a pool of mutations, responsible for different aminoacid substitutions, occured at this position. In NSCLC these mutations are present at a different frequency compared to colon and pancreatic cancer. It has been supposed that different aminoacids in the same position of KRAS protein could differently impact on tumor progression and drug resistance. To test this hypothesis, KRAS overexpressing clones with the three most common mutations found in NSCLC patients (G12C, G12D and G12V) have been generated in NCI-H1299 cell line. The clones showed a different response in vitro to cisplatin (Garassino MC et al, Annals of Oncology, 2011).

    Methods
    The clones were xenografted in nude mice to determine the antitumor activity of cisplatin in vivo. The effect of cisplatin on signalling pathways and DNA damage response was determined by western blotting, immunofluorescence and Real-Time PCR. Platinum adducts on DNA were revealed by DRC-ICP-MS.

    Results
    The resistance induced by the presence of G12C KRAS was still present compared to wild-type KRAS clone when these clones were transplanted in nude mice and treated with cisplatin. Some of the logic pathways functionally linked to KRAS, such as MAPK and PI3K, did not seem to account for the different cisplatin sensitivity observed. Factors previously reported to be associated to cisplatin resistance, such as the levels of cisplatin transporter CTR-1, of GSH and GST enzyme, and the total intracellular platinum levels were comparable among the clones. Several concordant results seem to indicate that, with a similar ability to enter the cells and to reach the DNA, an increased removal of platinum bound to DNA might account for the resistance of G12C clone: i) the cell cycle perturbation induced by cisplatin indicated that a reduced G2/M cell cycle phase block was observed in the G12C clone compared to all the others; ii) H2AX foci and ATM phosphorylations following treatment were barely detectable in the resistant clone; iii) the levels of platinum bound to DNA were much faster declining in G12C cells. The involvement in the resistance of G12C clone of Nucleotide Excision Repair and Fanconi Anemia repair mechanisms, which have been associated to the removal of adducts from DNA, was excluded by our experiments.

    Conclusion
    Altogether these data reveal the possibility that the presence of G12C KRAS mutation stimulates a DNA repair mechanism, not yet identified, able to faster remove platinum from DNA before the formation of double strand cross-links. Studies are ongoing to specifically address this point. Understanding why the different KRAS mutations influence the response to cisplatin could be useful in the clinical setting to tailor therapies for patients.