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S. Sakashita



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    MO12 - Prognostic and Predictive Biomarkers III (ID 96)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Medical Oncology
    • Presentations: 1
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      MO12.04 - Biomarker Analysis of NCIC Clinical Trials Group IND.196, a Phase I study of erlotinib plus foretinib in advanced pretreated non-small cell lung cancer patients (ID 3148)

      10:45 - 10:50  |  Author(s): S. Sakashita

      • Abstract
      • Presentation
      • Slides

      Background
      Upregulation of MET and more recently AXL have been described as potential mechanisms of resistance to EGFR tyrosine kinase inhibitors in NSCLC. We explored the impact of baseline MET and AXL tumour expression and circulating hepatocyte growth factor levels, (HGF), in advanced NSCLC patients receiving erlotinib plus foretinib, an oral multi-targeted kinase inhibitor of MET, RON, AXL, TIE-2 and VEGFR.

      Methods
      Advanced NSCLC patients that previously received one or two lines of chemotherapy were treated in IND.196, a phase I dose-finding trial with an initial two-week run-in of single agent erlotinib (100-150 mg daily). If erlotinib was well tolerated, foretinib was then added (30-45 mg daily). Submission of tumour samples (archival or fresh) was mandatory, and circulating HGF levels were determined at baseline and on treatment. Tumour samples were genotyped using Sequenom MassARRAY analysis. MET and AXL expression were determined by immunohistochemistry. For AXL, the human Axl affinity purified polyclonal goat IgG antibody (R&D systems, AF154, Minneapolis MN) was scored manually. For MET, the anti-total MET (SP-44) rabbit monoclonal antibody (Ventana Medical Systems, Tucson AZ) was scored using the Benchmark XT autostainer. Staining intensity (0-3+) and percent cells stained were used to calculate the H-score; H-scores >100 were deemed positive for AXL, and >200 positive for MET.

      Results
      Of 31 patients enrolled, 28 were evaluable for response to combination therapy, with a recommended phase II dose of erlotinib 150 mg daily for a 2-week run-in and then foretinib 30 mg daily added. The overall response rate in the intent to treat population (RECIST 1.1) was 16.1% (95% CI 5.5-33.7%), with partial responses (PR) seen in 5/31 patients and a median response duration of 17.9 months (range 3.6-17.9). Stable disease was seen in 42% (13/31), with a median duration of 4.8 months (95% CI 2.4-15.4). Tumour samples were submitted for 25 patients; 15 had sufficient tissue for genotyping, 17 for assessment of MET, and 16 for AXL expression. 2/5 responding patients had confirmed EGFR mutations, (1 wildtype, 2 unknown). Another 5 had KRAS mutations, one with >20% reduction in tumour size but SD by RECIST. Of 17 patients with MET IHC results, 71% (12/17) were positive. PR was seen in 3/12 patients with MET-positive tumours, (2 with EGFR mutations, 1 wildtype). No response was seen in those with MET-negative tumours. Of 16 samples with AXL IHC results, 9 were positive (56%). PR was seen in 2/9 with AXL-positive tumours and 2/6 with AXL-negative tumours. AXL expression was not seen in samples with EGFR mutations, but 3/5 KRAS mutant samples were AXL positive. Assessment of circulating HGF levels will be presented at the 2013 WCLC meeting.

      Conclusion
      Baseline MET expression, uncontrolled for EGFR status, may be associated with response to combination erlotinib/foretinib. No correlation between baseline AXL expression and response was seen although the sample size is small. Further study is needed to control for the impact of EGFR mutation status on response, and to assess whether combination erlotinib/foretinib can overcome resistance to EGFR TKI therapy mediated by MET and AXL.

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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): S. Sakashita

      • 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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    P2.06 - Poster Session 2 - Prognostic and Predictive Biomarkers (ID 165)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P2.06-023 - Gene expression signature and immunohistochemical assessment of NRF2 pathway activation for adjuvant chemotherapy benefit in lung squamous cell carcinoma (SqCC) (ID 1990)

      09:30 - 09:30  |  Author(s): S. Sakashita

      • Abstract

      Background
      Genomic profiling of SqCC has identified somatic alterations in NRF2 or its negative regulators (NFE2L2 mutations/amplifications, KEAP1 or CUL3 mutations/deletions) in ~1/3 of tumors. These alterations result in activation of the NRF2 transcriptional program, but the clinical significance of this pathway in lung SqCC patients is unknown. We hypothesize that a gene expression signature that reflects somatic NRF2-activating alterations may be identified and correlated with NRF2 protein over-expression. Furthermore, such gene expression or its immunohistochemical correlates may have prognostic significance and/or may be predictive of adjuvant chemotherapy benefit in early stage resectable lung SqCC patients.

      Methods
      Logistic regression (LR) and SAM analysis were applied independently to 104 SqCC cases from The Cancer Genome Atlas (TCGA) that had both microarray gene expression and mutation data to identify genes associated with NRF2 pathway mutational status. Overlapping genes were used to define the signature, which was then tested in 3 independent SqCC microarray datasets to evaluate its prognostic value. Correlation of the signature with NRF2 and KEAP1 mutations and with NRF2 and KEAP1 immunoreactive protein expression by immunohistochemistry (IHC) was evaluated. We also tested the gene expression signature as a potential predictor of adjuvant chemotherapy benefit in a subset of NCIC JBR.10 adjuvant chemotherapy trial patients with microarray data.

      Results
      A 28-gene signature that distinguished SqCC with or without aberration of the NRF2 pathway genes (NFE2L2/KEAP1/CUL3) in the TCGA dataset was identified. This gene signature that putatively represents NRF2 pathway activation status separates consistently SqCC into 2 groups in independent datasets. Both NRF2/KEAP1 mutation and NRF2 protein expression by IHC were significantly correlated with the NRF2 pathway activation signature (p<0.001 for each comparison). KEAP1 protein expression was not associated with the gene expression signature. No prognostic effect of the activated signature was observed in three independent datasets. In the JBR.10 patient cohort, a trend toward improved survival with adjuvant chemotherapy was observed in patients with the NRF2 “wild type” signature (HR 0.32, 95%CI 0.065-1.6 p=0.16), but not in patients with the “activated” signature (HR 2.28, 95%CI 0.24–22, p=0.48; interaction p=0.15).

      Conclusion
      A gene expression signature based on mutational activation of the NRF2 pathway may be predictive of benefit from adjuvant cisplatin/vinorelbine in SqCC. Patients with NRF2 pathway activating somatic alterations may have reduced benefit from this therapy. NRF2 immunohistochemistry could potentially be useful to identify NRF2-activated lung SqCC patients who may not benefit from adjuvant chemotherapy but this requires further validation.

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    P3.12 - Poster Session 3 - NSCLC Early Stage (ID 206)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Medical Oncology
    • Presentations: 1
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      P3.12-015 - Surgery for Early Non-Small Cell Lung Cancer with Preoperative Erlotinib (SELECT): A Correlative Biomarker Study (ID 2529)

      09:30 - 09:30  |  Author(s): S. Sakashita

      • Abstract

      Background
      Erlotinib has demonstrated major activity in EGFR mutation positive NSCLC, but may also benefit those with wild type tumours. We conducted a single-arm trial of pre-operative erlotinib in early stage NSCLC to assess radiologic and functional response as well as correlation with known and investigational biomarkers.

      Methods
      Patients with clinical stage IA-IIB NSCLC received erlotinib 150 mg daily for 4 weeks followed by surgical resection. Tumor response was assessed using pre- and post-treatment CT and PET imaging. Tumor genotype was established using Sequenom MassARRAY analysis. EGFR, PTEN, cMET and AXL expression levels were determined by immunohistochemistry. Pre- and post-treatment circulating markers/ligands for EGFR activation (TGF-α, amphiregulin, epiregulin, EGFR ECD) were measured by ELISA. Tumor MET copy number by FISH and VeriStrat® analysis of pre-treatment serum samples is ongoing. Secondary endpoints included pathological response, toxicity and progression-free survival.

      Results
      Twenty-five patients were enrolled; 22 received erlotinib treatment with a median follow up of 4.4 years (range 2.2 to 6.4 years). Histology was predominantly adenocarcinoma (15) with smaller numbers of squamous cell carcinoma (7). PET response (25% SUV reduction) was observed in 2 patients (9%), both with confirmed squamous carcinoma histology. All patients met criteria for stable disease by RECIST and several experienced minor radiographic regression with histologic findings of fibrosis/necrosis, including 2 with squamous histology. The presence of an EGFR activating mutation was detected in two adenocarcinoma cases; one patient experienced minor radiographic response to treatment (exon 19 deletion) and the other stable disease (L858R). High pre-treatment serum levels of TGF- α correlated with tumor growth or primary resistance to erlotinib therapy (p=0.04), whereas high post-treatment soluble EGFR levels correlated with tumor response (p=0.02). Expression of EGFR, PTEN, cMET and AXL did not correlate significantly with tumor response.

      Conclusion
      Erlotinib appears to demonstrate some activity in EGFR wild-type tumors including those with squamous histology. These findings support that certain EGFR wild-type patients may respond to EGFR TKIs. Further research is needed to characterize these patients and elucidate the predictive ability of potential biomarkers such as TGF- α, EGFR copy number and others.