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M. Li



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    MO01 - Lung Cancer Biology - Techniques and Platforms (ID 90)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      MO01.09 - A novel murine xenograft model using samples obtained by EBUS-TBNA (ID 773)

      11:10 - 11:15  |  Author(s): M. Li

      • Abstract
      • Presentation
      • Slides

      Background
      Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) is a minimally invasive approach for lymph node staging in patients with lung cancer. Although EBUS-TBNA has been utilized for various molecular testing, intrinsic characteristics of different lesions produce variability in the amount of cellular material that can be obtained. In some samples, the quantity of tumor recovered may be limited for subsequent testing. To overcome this problem, we evaluated the feasibility of establishing a murine tumor xenograft model using EBUS-TBNA samples for advanced translational research.

      Methods
      After confirmation of adequate sampling for cytopathological diagnosis during EBUS-TBNA, one additional pass was performed for this study (NCT01487603). The aspirate was stored in cell preservative solution (RPMI1640 with 10% FBS) for inoculation of the tumor for the xenograft model. The sample was transported to the laboratory on ice, then mixed with Matrigel and centrifuged. The pellet which contained tumor fragments was implanted to the subcutaneous pocket on the right flank of a NSG (NOD scid gamma) mouse. Once we confirmed the engraftment of the tumor, we passed the tumor to another mouse until 3 passages were completed. The success rate of tumor xenograft establishment was examined along with histopathology and the cellularity and cytopathologial diagnosis of the primary EBUS-TBNA samples.

      Results
      From December 2011 to June 2012, 19 patients were enrolled in this study. The cytopathological diagnoses were as follows; 12 adenocarcinoma, 3 squamous cell carcinoma, 1 large cell carcinoma NOS, and 3 small cell carcinomas. 8 out of 19 cases (42.1%) showed tumor formation. The mean duration between inoculation and tumor formation was 62.38 days (13-144 days). All engrafted tumors could be passed to the second mouse. The histological types of the engrafted tumors were 3 adenocarcinoma (3/12: 25%), 2 squamous cell carcinoma (2/3: 67%), 1 large cell carcinoma (1/1: 100%), and 2 small cell carcinomas (2/3: 67%). The tumor cellularity of primary EBUS-TBNA samples was sufficient for diagnosis and there was no correlation between engraftment and the degree of blood/lymphocyte contamination or percentage of necrosis.

      Conclusion
      EBUS-TBNA samples can be used for establishment of tumor xenograft model in immunodeficient mice. EBUS-TBNA allows minimally invasive sampling of metastatic lymph nodes in patients with advanced lung cancer which opens up possibilities for translational research. We need to continuously seek better ways to improve and standardize procurement and processing of samples obtained by minimally invasive techniques in order to optimize diagnosis and molecular analysis for improved patient care. Figure 1

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    O08 - Preclinical Therapeutic Models I (ID 92)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      O08.07 - Patient-derived primary non-small cell lung carcinoma (NSCLC) xenograft models for mechanistic studies of resistance to EGFR tyrosine kinase inhibitor therapy (ID 2380)

      17:10 - 17:20  |  Author(s): M. Li

      • Abstract
      • Presentation
      • Slides

      Background
      Non-small cell lung cancer (NSCLC) patients with tumors bearing “driver” mutations in the epidermal growth factor receptor (EGFR) tyrosine kinase (TK) domain have very high response rates to small molecule EGFR TK inhibitors (TKIs). However, all patients eventually develop resistance to the TKIs, and more recent reports have shown that patients who have stopped TKI therapy may be sensitive again upon re-treatment. While several genetic mechanisms of resistance have been documented, including the gate keeper T790M mutation and Met amplification, cell line studies in vitro have also implicated alternate epigenetic mechanisms that may explain the clinical progression observed in patients with EGFR mutations treated by TKIs. Studies in vivo using patient-derived primary lung tumor xenograft models have not been reported.

      Methods
      Patient-derived primary tumor xenografts were established from surgically resected early stage NSCLC implanted subcutaneously in non-obese diabetic severe combined immune deficient (NOD-SCID) mice. Tumors were passaged after reaching the humane endpoint 1.5 cm maximum diameter. EGFR TKI therapy was initiated when tumors reached ~6 mm diameter. Treatment included daily oral gavage for erlotinib (50 mg/Kg) and dacomitinib (3 mg/Kg). Cetuximab was administered weekly intraperitoneally (50 mg/Kg).

      Results
      Among 33 tumors with EGFR mutations engrafted into the mice, only 6 (18.2 %) formed tumors that could be propagated beyond first passage. Three models have been studied for their responses to EGFR TKIs. Model 148 with L858R mutation showed intrinsic pan-resistance to erlotinib and dacomitinib, as well as to cetuximab. This model was derived from a patient who received pre-operative erlotinib in a window of opportunity trial and did not respond. The patient relapsed after surgery and did not receive additional TKI therapy. Model 137 with exon19 E746-A750 deletion mutation demonstrated complete response to both erlotinib and dacomitinib. However, microscopic examination of tissue from the implantation site revealed viable tumor cells, consistent with the inability of TKI to completely eradicate tumor cells even when complete response is observed clinically. The patient subsequently developed disease recurrence and responded to third line gefitinib treatment. Model 164 has double exon19 L747-T751 deletion/T790M mutations. As anticipated, the xenograft failed to respond to erlotinib but responded dramatically to cetuximab alone. Importantly, model 164 xenograft showed transient stabilization of the tumor growth when treated by dacomitinib, but eventually developed progressive growth after 2 weeks of treatment. Resistance was reversible each time the dacomitinib-resistant tumor was propagated, without drug in new mice. The reversibility of resistance observed upon re-initiation of dacomitinib treatment suggests an epigenetic mechanism for TKI resistance. This patient developed recurrence after surgery and failed to respond to second line erlotinib treatment.

      Conclusion
      Patient-derived primary lung cancer xenografts may provide important patient-like models to study mechanisms of resistance to targeted therapies, and to test novel treatment strategies that may improve further treatment efficacy.

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    P1.05 - Poster Session 1 - Preclinical Models of Therapeutics/Imaging (ID 156)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P1.05-007 - Large scale establishment of genetically diverse patient-derived primary tumor xenografts from resected early stage non-small cell lung cancer (NSCLC) patients (ID 1539)

      09:30 - 09:30  |  Author(s): M. Li

      • Abstract

      Background
      The fidelity of established NSCLC cell line models to reflect patient tumors has been challenged. Patient-derived primary tumor xenografts (PTXGs) established directly from patient tumors in immunodeficient mice reproduce closely the histology of the primary tumors, thus are potentially better preclinical models to investigate novel therapies. We previously reported that early stage NSCLC patients whose tumors form PTXGs have significantly greater risk of relapse after surgery (Clin Cancer Res 2011; 17: 134-141). We report here a more extended analysis of clinical-molecular-pathological features of early stage NSCLC that are associated with engraftment and its impact on patient outcome.

      Methods
      Resected NSCLC tumors were harvested within 30 minutes after surgery and were implanted into severely immunodeficient mice to establish PTXGs. Tumors that grew were propagated for up to 3 passages. The mutational profiles of the primary tumors were assessed by the MassARRAY platform that included 133 mutations with ‘putative’ driver function, which have been reported in COSMIC database as recurrent in NSCLC. All identified mutations were verified by direct sequencing in both the primary and PTXG tumors. Engraftment rate among clinical factors were tested using the Fisher’s exact or Mann-Whitney tests. The Kaplan-Meier method was used to estimate 3-year overall (OS) and disease-free survival (DFS) probabilities. The effect of engraftment on OS and DFS adjusting for clinical variables was assessed using a Cox proportional hazards model.

      Results
      From April 2005 to December 2010, 261 rigorously verified resected primary non-carcinoid NSCLCs were engrafted; 38 xenografts that were lymphoma were excluded from further analysis. For the remaining 223 primaries, 101 (45.3%) successfully engrafted and formed PTXG lines. Engraftment rates were 33.8% (48/142) for adenocarcinoma (AdC), 67.7% (42/62) for squamous cell carcinoma (SqCC), 66.7% (4/6) for large cell neuroendocrine carcinoma, and 53.8% (7/13) for others. The tumors forming PTXGs were more likely to be poorly differentiated (p=0.00012) and of larger tumor size and higher pT stage (p<0.0001), but were not correlated with the pN stage. Among 95/101 (94.1%) PTXG cases profiled for mutations, 6 had mutations in the EGFR tyrosine kinase domain, 18 in KRAS/HRAS, 5 in PIK3CA, 2 in paxillin and 1 in STK11/LKB gene; 56 (62.2%) were negative for mutations. The median follow-up time was 2.7 years (range 0.04 – 7.5 years). Patients whose tumors engrafted had decreased DFS (HR 2.68, 95% CI 1.16-4.60, Wald p<0.0001) and OS (HR 3.14, 95% CI 1.56-6.33, Wald p=0.0014). Significantly poorer survival was maintained in AdC. Among 33 patients with EGFR mutation, only 6 (18.2%) engrafted. Engraftment was associated with significantly poorer DFS (HR 4.76; 1.43-15.86, log-rank p=0.005) and OS (HR 8.55, 95% CI 0.77-94.3, log-rank p=0.035) in this population.

      Conclusion
      The ability to form PTXGs of early stage NSCLC is confirmed as a very strong poor prognostic marker. Although EGFR mutant tumors usually do not engraft, engraftment of EGFR mutant tumors is associated with poor patient survival. PTXGs appear to represent biologically aggressive NSCLC.