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  P3.01 - Poster Session 3 - Cancer Biology (ID 147)

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

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    P3.01-012 - Co-targeting the PI3K and MEK pathways in NSCLC: an in vitro evaluation and mutation prevalence in an Irish patient cohort. (ID 2794)

    09:30 - 09:30  |  Author(s): S. Toomey
    • Abstract

    Background
    PI3K pathway activation in NSCLC has been shown by us and others to lead to a more aggressive disease correlating to poor prognosis for patients. Unfortunately, the success of PI3K targeted inhibition has been hampered by a high rate of innate and acquired resistance. Mutations in KRAS and B-RAF, ERK hyperactivation as well as extensive PI3K-MEK pathway cross-talk allow the MEK pathway to provide a bypass track. Preclinical studies demonstrate a rationale for a PI3K-MEK co-targeted treatment strategy which may provide a more effective response. A Phase I clinical trial is underway investigating the combination of GDC-0941, a pan-PI3K inhibitor, with GDC-0973, a MEK inhibitor. GDC-0980 is a dual PI3K-mTOR inhibitor which may offer improved pathway inhibition compared to GDC-0941. No data has been published to date on the combination of GDC-0980 and GDC-0973, which we believe may offer improved overall inhibition of survival signaling in NSCLC cells. We aim to elucidate the role of mutation status in response to this co-targeted inhibition approach in vitro, as well as investigating the frequency of PI3K and MEK pathway mutations in a well characterized Irish NSCLC patient cohort.

    Methods
    The effects of GDC-0941, GDC-0980 and GDC-0973 on proliferation and apoptosis in a panel of four NSCLC cell lines were analysed by BrdU Assay and HCA Apoptosis Assay, respectively. The four cell lines investigated were H460 (adenocarcinoma, PIK3CA mutant & KRAS mutant), A549 (adenocarcinoma, PIK3CA wild type & KRAS mutant), H1975 (adenocarcinoma, PIK3CA mutant, KRAS wild type & EGFR TKI resistant) and SKMES-1 (squamous cell carcinoma, PIK3CA wild type & KRAS mutant). Further investigation involved expression analysis of pAkt, pGSK-3β, pp70S6K, pS6RP, ERK and pERK in cell lines treated with each inhibitor alone or in combination using Mesoscale technology and Western blot. DNA was extracted from 120 NSCLC patient tissue samples, and screened for 547 mutations in 59 genes (including PI3K and MEK pathway members) using the Sequenom.

    Results
    GDC-0941 and GDC-0980 treatment induced dose-dependent anti-proliferative and pro-apoptotic responses across all four NSCLC cell lines, while GDC-0973 treatment induced only anti-proliferative responses. Protein expression analysis showed that GDC-0980 & GDC-0973 combination treatment induced significantly improved phosphoprotein inhibition compared to treatment with either inhibitor alone in cell lines harbouring PIK3CA mutations, while in one cell line bearing WT PIK3CA (SKMES-1), combination treatment actually increased pathway signalling. NSCLC patient mutational profiling data will be presented.

    Conclusion
    This research underpins the importance of mutation status in sensitivity to targeted therapies. While combination treatment approaches may be beneficial in certain molecular subtypes, in others they may be detrimental. In the era of personalised medicine, patient genotyping is crucial to improve patient survival and reduce toxicities.