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J.E. Larsen



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    O12 - Lung Cancer Biology II (ID 87)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      O12.05 - Defining the role of ZEB1 in the pathogenesis of non-small cell lung cancer (NSCLC) using immortalized human bronchial epithelial cells (HBECs) (ID 1139)

      10:30 - 12:00  |  Author(s): J.E. Larsen

      • Abstract
      • Presentation
      • Slides

      Background
      To study the role of common lung cancer mutations in transforming lung epithelial cells in an appropriate cellular context we used cdk4/hTERT-immortalized normal HBECs. We developed an isogenic series of HBECs by introducing genetic manipulations representing common lung cancer mutations (such as p53, KRAS[V12], cMYC, and LKB1). This defined in vitro system allows characterization of specific tumorigenic contributions as well as identification of acquired changes, likely representing tumor acquired vulnerabilities and novel therapeutic targets (Mol Cancer Res 2013). One acquired change observed with oncogenic transformation of HBECs is a spontaneous epithelial-to-mesenchymal transition (EMT), an important biologic process in cancer. This study sought to characterize the role of EMT in driving tumorigenesis in HBECs and, in turn, lung cancer to identify novel therapeutic targets.

      Methods
      Genetic manipulations were introduced into cell lines using siRNA/shRNA or over-expression constructs. Tumorigenicity was measured using in vitro (anchorage-dependent and -independent colony formation, proliferation, migration and transwell Matrigel invasion assays) and in vivo (subcutaneous or intravenous injection into NOD/SCID mice) methods. Genome-wide mRNA expression data from five independent datasets was obtained either in-house using Illumina HumanHT-12v4 BeadChips or from publicly available databases.

      Results
      Analysis of EMT-promoting transcription factors in our isogenic series of oncogenically-manipulated HBECs found ZEB1 expression highly correlated with mesenchymal-like HBECs. Functional studies confirmed ZEB1 was a significant driver of tumorigenic phenotypes in both oncogenic HBECs and human lung cancer cell lines where loss of ZEB1 resulted in decreased colony formation, migration and invasion in vitro and subcutaneous tumor growth and intravenous colonization in vivo. A set of ZEB1-associated genes was identified from analyzing five independent mRNA microarray datasets comprising both cell lines and lung adenocarcinomas. From this gene set we found ZEB1 directly represses ESRP1 by binding to its promoter, which leads to increased mesenchymal splicing of the ESRP1 target CD44. The mesenchymal isoform of CD44, CD44s, conferred a CD44[hi] flow cytometry profile which, in turn, could be used to select for a highly tumorigenic subpopulation in partially transformed HBECs. To identify candidate ZEB1-activated targets we screened ZEB1-upregulated genes in a siRNA invasion assay. Several genes including PMP22 and CD70 could phenocopy ZEB1 where siRNA-mediated loss of expression led to decreased invasiveness in multiple NSCLC cell lines. CD70 (also called TNFSF7, tumor necrosis factor ligand superfamily member 7) may represent a prime therapeutic target for anti-metastatic growth in lung cancer. The ligand for CD27, it is involved in immune regulation, upregulated in some cancers and is being studied as a potential target for antibody therapeutics. Importantly, an anti-CD70 monoclonal antibody inhibited invasion of NSCLC cell lines comparably to siCD70 and siZEB1.

      Conclusion
      We demonstrate in vitro models of defined oncogenic HBEC transformation provide an invaluable tool to study lung cancer progression where EMT is an important mediator. ZEB1 is spontaneously expressed with malignant transformation of HBECs and is a significant driver of oncogenic progression in both HBECs and NSCLC cells. Identification of CD70 and PMP22 as downstream targets of ZEB1 may represent novel therapeutic targets for lung cancer.

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

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P3.01-011 - Heterogeneity in tumour content and necrosis in primary lung cancers: Implications for molecular analysis (ID 3326)

      09:30 - 16:30  |  Author(s): J.E. Larsen

      • Abstract

      Background
      Lung adenocarcinoma (AC) and squamous cell carcinoma (SCC) tumours have a large variance in tumour cell content. This heterogeneity is a concern for genomic studies, as it is difficult to distinguish mutational differences between tumour and non-tumour if low percentage tumour is used for analysis. In addition to this, tumour samples are affected by the amount of necrosis present, as the overall number of viable cells is decreased. We assessed tumour and necrotic content in lung tumour specimens from AC and SCC patients and aimed to identify possible implications for the suitability of these samples in molecular characterisation studies using next generation sequencing technology.

      Methods
      Lung tissue specimens were collected during the period of 1990 to 2013 from patients at The Prince Charles Hospital who consented to donate their surgically resected lung tissues for research. Tissues were macroscopically dissected, snap frozen in liquid nitrogen and stored at -80°C. A tissue section was taken and stained with haematoxylin and eosin (H&E) for two pathologists to independently assess tumour cell and necrotic content. Tumour cell content (TC) in each specimen was scored as percentage of viable cells as seen on the H&E slide, where necrotic content (NC) was recorded as a percentage of the whole slide section. Statistics were calculated using SPSS v21 software. Tumour specimens screened for eligibility to The Cancer Genome Atlas sequencing project are presented here.

      Results
      Tumours from 62 AC and 104 SCC subjects were scored (specimen characteristics in Table 1). Scoring between the two pathologists was highly correlated, with a high intraclass reliability (0.94 and 0.96 for TC and NC respectively).

      Table 1: Clinical and Pathological Characteristics of Specimens
      AC SCC
      Number of Specimens 384 609
      Number of Males/Females 36/26 84/20
      Median Specimens per Subject 4 4
      Range of Specimens per Subject 1-25 1-27
      Median TC 35% 30%
      Range of TC 0-88% 0-90%
      Median NC 0% 6%
      Range of NC 0-90% 0-100%
      Median Age 62 yrs 68 yrs
      Range of Age 45-85 yrs 46-91 yrs
      Median Smoking Pack Years 40 56
      Range of Smoking Pack Years 0-115 0-158
      TC varied from 0-~90% for both subtypes. Comparing AC and SCC, the median TC was higher in AC than SCC (35% vs 30% respectively, p<0.05). NC varied from 0-~100%, but was generally low. The median NC was statistically significantly different between AC and SCC (0% and 6% respectively, p<0.001). TC was weakly correlated with NC (Spearman Rank r = 0.32, p<0.01). There were no clinically important correlations between smoking pack years, gender or age with TC and NC of specimens.

      Conclusion
      Lung AC and SCC specimens are heterogeneous in terms of TC and NC. Therefore, only a small proportion of resected lung cancer specimens meet the criteria required for massively parallel sequencing projects that require high quality tumour DNA and RNA (ie low NC) and relatively low stromal contamination (ie high TC).