Author of

• 11454

  +

  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

  • 11470

    +

    P2.01-016 - Targeting the PI3K-mTOR-NFκB pathway to overcome cisplatin resistance in NSCLC. (ID 2788)

    09:30 - 09:30  |  Author(s): C. Edwards
    • Abstract

    Background
    Non-small cell lung cancer (NSCLC) is the leading cause of cancer morbidity and mortality in the Western world with a poor overall 5 year survival of <15%. The most effective systemic chemotherapy for NSCLC is cisplatin-based combination treatment. However, chemoresistance is a major therapeutic problem and understanding the mechanisms involved is critical to the development of new therapeutic intervention strategies. The PI3K pathway plays an important role in NSCLC and we and others have shown increased PI3K signaling to be associated with a more aggressive disease with poor prognosis. Several proteins in this pathway have been indicated as potential mediators of cisplatin resistance in other cancers, and our group has previously identified the PI3K-activated transcription factor NFκB as a key player in this setting. In this study, targeted inhibition of three strategic points of the PI3K pathway was carried out with the aim of overcoming acquired resistance to cisplatin in these cell lines.

    Methods
    A panel of cisplatin resistant cell lines was previously generated in our laboratory through prolonged exposure to the drug. Expression of PI3K pathway related genes was compared between H460 parent (H460PT) and H460 cisplatin resistant (H460CR) cells using a PI3K pathway SABiosciences RTPCR array. Identified genes of interested were further investigated via PCR and Western blot in these cells as well as A549 parent (A549PT) and A549 cisplatin resistant (A549CR) cells. Three strategic points of the pathway were inhibited using GDC-0980, a dual PI3K-mTOR inhibitor currently in Phase II clinical trials in NSCLC, and DHMEQ, an inhibitor of NFkB translocation which has been used extensively both in vitro and in vivo. Effects of the two inhibitors on the parent & cisplatin resistant cell lines both with and without cisplatin were assessed by BrdU proliferation assay and multiparameter apoptosis assay (High Content Analysis).

    Results
    One of the most notable targets to emerge from the PI3K pathway RTPCR array screen was NFKBIA; the gene which codes for NFκB inhibitor IκBα. This gene was shown to be 12 fold overexpressed in H460CR compared to H460PT. This finding was validated at both the RNA and protein level by PCR and Western blot. NFκB was also found to be overexpressed in cisplatin resistant cells compared to their respective parent cells. Inhibition of NFκB by DHMEQ led to significantly improved inhibition of proliferation and induction of apoptosis in cisplatin resistant cells compared to parent cells. Preliminary data indicates that inhibition of PI3K and mTOR by GDC-0980 did not offer as significant a benefit as inhibition of NFκB in the cisplatin resistance setting, though further data from combination studies will be presented.

    Conclusion
    We conclude that the PI3K pathway plays an important role in resistance to cisplatin in NSCLC, particularly when signaling proceeds through the transcription factor NFκB. Targeting this pathway may be of benefit in re-sensitizing cisplatin resistant tumours to the drug.