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• 11515

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  P2.05 - Poster Session 2 - Preclinical Models of Therapeutics/Imaging (ID 158)

  • Event: WCLC 2013
  • Type: Poster Session
  • Track: Biology
  • Presentations: 2
  • Moderators:
  • Coordinates: 10/29/2013, 09:30 - 16:30, Exhibit Hall, Ground Level

  • 11519

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    P2.05-004 - Synergistic antitumor activity of bevacizumab and erlotinib in EGFR-mutated non-small cell lung cancer xenograft models (ID 310)

    09:30 - 09:30  |  Author(s): Y. Moriya
    • Abstract

    Background
    Erlotinib (ERL), a specific inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, benefits patients with non-small cell lung cancer (NSCLC), especially if the cancer harbors EGFR active mutations (mtEGFR). However, those who initially respond eventually develop progressive disease through acquired resistance. Bevacizumab (BEV), a humanized anti-vascular endothelial cell growth factor monoclonal antibody, has been demonstrated to be effective in combination with standard chemotherapies for advanced NSCLC patients. We hypothesized that the combination of the two agents may be more effective because they work through different modes of action. In the present study, we examined the antitumor activity of BEV in combination with ERL in human NSCLC xenograft models harboring mtEGFR.

    Methods
    Mice (BALB-nu/nu) were subcutaneously inoculated with NSCLC cell lines harboring mtEGFR (exon19 deletion); HCC827 and B901L. BEV (5 mg/kg) was intraperitoneally administered once a week for 3 weeks, and ERL was orally given daily for 21 days at doses of 5 and 40 mg/kg for HCC827 and B901L, respectively. Antitumor activity was evaluated by tumor volume (TV; mm[3]) on day 22. In order to examine the prolonged antitumor effect of the combination of BEV with ERL, the B901L xenograft model was used. BEV (5 mg/kg) was intraperitoneally administered once a week for 13 weeks and ERL (60 mg/kg; maximum effective dose) was orally given daily for 91 days. The antitumor activity was evaluated on day 92, with an interim evaluation on day 22. The microvessel density (MVD) of tumor tissues was evaluated by CD31 immunohistochemistry of specimens obtained on day 2 from mice treated with BEV (5 mg/kg) and ERL (40 mg/kg). Statistical analysis was performed using the Wilcoxon test.

    Results
    In the HCC827 model, the TV (mean±SD) of control, BEV, ERL, and BEV+ERL was 1300±424, 686±84, 615±185, and 194±29, respectively. In the B901L model, the TV of control, BEV, ERL, and BEV+ERL was 1739±761, 819±293, 294±198, and 57±19, respectively. The antitumor activity of BEV+ERL was significantly better than that of BEV or ERL monotherapy (p≤0.05) in both models. In the prolonged treatment experiment using B901L, on day 22, BEV (1096±298) showed significantly higher (p≤0.05) tumor growth inhibition than control (2452±731), but the ERL (61±31) and BEV+ERL (53±30) showed even better (p≤0.05) tumor regression effects than BEV. However, during further treatment, tumor regrowth was observed in the ERL group, even though ERL was consecutively given, and the TV on day 92 (1105±1001) was significantly greater than that on day 22 (61±31). Tumor regrowth was also observed in the BEV+ERL group; however, it was much slower compared to the ERL group and there was no significant difference between TV on day 92 (79±70) and that on day 22 (53±30). The MVD was significantly decreased to the same level in the BEV and BEV+ERL groups.

    Conclusion
    Compared to ERL monotherapy, the combination of BEV and ERL demonstrated promising efficacy in mouse models of NSCLC harboring EGFR activating mutations. The encouraging preclinical results warrant further investigation in a clinical setting.

  • 11522

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    P2.05-007 - Significance of the recommended dose erlotinib for avoiding acquired resistance in NSCLC cells with exon19 deletion and L858R mutation of EGFR (ID 738)

    09:30 - 09:30  |  Author(s): Y. Moriya
    • Abstract

    Background
    Erlotinib, an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, shows notable effects against non-small cell lung cancers (NSCLCs) harboring EGFR-activating mutations such as exon 19 deletion or L858R mutation. However, almost all patients eventually acquire resistance to erlotinib. In this study, we investigated whether the level of exposure to erlotinib affects incidence of acquired resistance in EGFR-mutated NSCLC cell lines and examined their resistant mechanisms.

    Methods
    Human NSCLC cells B901L and PC-9 harboring exon 19 deletion and II-18 cells with L858R mutation were continuously exposed to 0.5 or 5 µM of erlotinib in 96-well plates for several months. The upper dose was chosen because the recommended dose of erlotinib (150 mg) has been reported to achieve maximum plasma concentration (Cmax) of about 5 µM. Cell growth inhibition was determined by a crystal violet assay. EGFR mutation status was determined by melting curve analysis. MET copy number was determined by real-time PCR analysis. Phosphorylations of EGFR, HER2 and ERK were measured by Western blot analysis.

    Results
    Resistant B901L, PC-9 and II-18 cells were emerged in 24, 8 and 7 wells by exposing to 0.5 µM erlotinib, and in 13, 2 and 0 wells by exposing to 5 µM erlotinib, respectively. No alterations in EGFR mutation status including T790M mutation nor acquisition of MET amplification were detected in any resistant cells. In parent cells, treatment with erlotinib markedly inhibited phosphorylation of EGFR, HER2 and ERK. In the parent cells, treatment with erlotinib markedly inhibited EGFR phosphorylation but not HER2 and ERK phosphorylation, compared with the parent cells.

    Conclusion
    In present in vitro analysis, it was suggested that exposure to the recommended dose of erlotinib would avoid acquired resistance in NSCLC with exon19 deletion or L858R mutation of EGFR. Pathways activated by phosphorylated HER2 may affect acquired resistance to erlotinib.