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E.L. Stewart



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    P2.03b - Poster Session with Presenters Present (ID 465)

    • Event: WCLC 2016
    • Type: Poster Presenters Present
    • Track: Advanced NSCLC
    • Presentations: 1
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      P2.03b-077 - EGFR/ALK+ Patient-Derived Xenografts from Advanced NSCLC for TKI Drug Selection & Resistance Development: The REAL-PDX Study (ID 6081)

      14:30 - 14:30  |  Author(s): E.L. Stewart

      • Abstract

      Background:
      Lung cancer patient-derived xenografts (PDX) have shown to be representative models for individual patient tumors. Theoretically, such models could inform the choice of subsequent lines of therapy, since PDX development, TKI resistance induction, and subsequent drug-screening can be completed before TKI resistance develops in the patient. The goal of Resistance modeling in EGFR and ALK Lung cancer (REAL)-PDX is to develop PDX models for real-time treatment selection of subsequent lines of therapy in advanced-stage NSCLC patients.

      Methods:
      Since August 2015, Princess Margaret Cancer Centre patients with EGFR/ALK+, as well as lifetime never-smoking lung cancer patients with unknown mutation status, were consented to have additional tumor sampling for PDX development during routine- or trial-related biopsies. Tumor sufficiency was confirmed prior to implantation into non-obese severe combined immunodeficient (NOD-SCID) mice, with successful engraftment defined as propagation beyond first passage; unsuccessful implantations had no palpable tumor after 6 months.

      Results:
      72/82 (88%) approached patients consented; 49/72 (68%) had adequate tumor tissue for implantation (71% stage III/IV): 46 adenocarcinomas, 2 squamous cell carcinoma, 1 LCNEC. 36/49 (73%) were lifetime never smokers. Patients received adjuvant chemotherapy (3), TKI therapy (15), both (5), or no treatment (26) prior to sampling. Tumor samples were taken from surgically resected lung (18), metastatic adrenal (1) and brain (2), CT-guided lung biopsies (5), endoscopic ultrasound-guided (EBUS) biopsies (6), and thoracentesis pleural fluid (17) specimens. Twenty-eight implanted tumors were EGFR+ (12 exon19 deletions, 2 exon19 deletion/T790M, 1 exon19 del/exon18 mutation, 12 L858R, and 1 L858R/T790M); 7 had ALK-rearrangements, and 1 had ROS1-rearrangement. Engraftment rates of 31 assessable implanted tumors were as follows: lung resections 12/12 (100%), metastatic resections 2/3 (67%), CT- or EBUS-guided biopsies 1/5 (20%), and pleural fluid 2/11 (18%); Engraftment rate was associated with no prior treatment (14/17 no treatment vs 3/14 any treatment, p=0.001). Of 17 assessable tumors with EGFR activating mutations, 9 engrafted (53%). Of 3 assessable tumors with ALK-rearrangement, 1 was successful (33%).

      Conclusion:
      PDX development of EGFR/ALK+ models for testing with novel therapeutics from various tumor biopsy sites is feasible and will provide valuable real-time information for subsequent treatment decisions in advanced NSCLC patients. Updated engraftment and drug screening data will be presented.

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    P3.02b - Poster Session with Presenters Present (ID 494)

    • Event: WCLC 2016
    • Type: Poster Presenters Present
    • Track: Advanced NSCLC
    • Presentations: 1
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      P3.02b-028 - Characterizing Residual Erlotinib-Tolerant Population Using EGFR-Mutated NSCLC Primary Derived Xenografts: The Last Holdouts (ID 5455)

      14:30 - 14:30  |  Author(s): E.L. Stewart

      • Abstract

      Background:
      Three generations of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have led to multi-fold improvements in progression free survival of advanced stage non-small cell lung cancer (NSCLC) patients carrying EGFR kinase domain mutations. However, cure is not yet achievable with any EGFR TKI monotherapy, as patients will eventually progress due to acquired resistance. In vitro evidence suggests that minor populations of epigenetically modified drug tolerant cells (DTCs) may be one important mechanism for tumor cells surviving the TKI. We hypothesize that characterizing the genomic and epigenomic alterations observed in DTCs in vivo and comparing them to the bulk tumour will delineate a number of mechanisms of tolerance exhibited by DTCs.

      Methods:
      DTCs were induced via chronic erlotinib treatment of a lung adenocarcinoma primary derived xenograft (PDX) harbouring an erlotinib sensitive exon 19 deletion. Molecular profiles of DTCs are compared to untreated controls via immunohistochemistry (IHC) and gene expression array. We are now undertaking exome-sequencing, assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), methylated DNA immunoprecipitation and sequencing (MeDIP-seq).

      Results:
      When compared to untreated tumours, DTCs exhibit decreased apoptosis (CC3 IHC) and proliferation (Ki67 IHC). DTCs maintained strong signaling via the EGFR pathway (pERK, pAKT, pS6). DTCs exhibited 2437 significantly differentially expressed genes (DEGs; >1.5-fold change and adjusted p-value <0.05) including multiple cancer stem cell markers (ALDH1A1, ALDH1A3, CD44). DEGs also were involved in vesicle-mediated transport (including lysosomes, exosomes and endosomes), autophagy, stress/unfolded protein response, cytoskeleton organization, chromatin organization, ion pumps and transporters, cell adhesion, WNT, NOTCH, PI3K and MAPK pathways. DTCs remained resistant to three cycles of cisplatin/vinorelbine either alone or when combined with erlotinib. Genomic and epigenomic profiling are on-going and results will be presented.

      Conclusion:
      DTCs may be a major impediment to cure by single-agent EGFR targeted therapies. Understanding the mechanisms and developing strategies to overcome DTCs may give insights on therapeutic strategy to further improve the survival of EGFR-mutated NSCLC patients.