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D.T. Merrick



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    MO04 - Lung Cancer Biology I (ID 86)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      MO04.05 - Tracheal basal cells in the lung squamous dysplasia: moving proximal. (ID 1700)

      16:35 - 16:40  |  Author(s): D.T. Merrick

      • Abstract
      • Presentation
      • Slides

      Background
      Squamous cell carcinoma (SCC) is the second most common form of lung cancer, a disease primarily observed in smokers. Studies have shown that preneoplastic dysplasias are the precursors for SCC. However, only a subset of these lesions progress to invasive carcinoma and predicting the fate of individual lesions is difficult. Understanding the processes associated with the development of dysplasia would therefore have significant impact on preventative therapy for high-risk lesions. To this goal we have studied N-nitroso-tris chloroethyl urea (NTCU) model of premalignant murine squamous dysplasia. Bi-weekly topical application of NTCU for 32-weeks caused endobronchial dysplasias that were pathologically similar to dysplasias encountered in human smokers. In the current study we used NTCU model to identify the events that precede dysplastic changes in murine airways.

      Methods
      Immunofluorescence analysis of NTCU treated airways showed abundant expression of keratin 5 positive (K5+) basal cells. In normal mouse respiratory epithelium K5+ cells are confined only in the trachea and are absent in the bronchial epithelium. Ectopic expressions of K5+ cells in the mouse bronchial epithelium therefore suggested a role for tracheal basal cells in the pathogenesis of NTCU-induced dysplasia. To explore this possibility we analyzed tracheal and bronchial histology after vehicle and 20mM NTCU treatment at 4, 8, 12, 16, 25 and 32 weeks.

      Results
      Low-grade dysplasia of the tracheal epithelium was observed as early as 4 weeks of NTCU exposure. On the contrary, squamous metaplasia or low-grade dysplasia of the bronchial epithelium was not seen until 25 weeks. Morphometric analysis of immunostained tracheal tissue showed a time-dependent increase in the numbers of K5+ cells and a concomitant loss of cells expressing Clara cell secretory protein (CCSP) and ciliated cells. We have shown previously that injury to the trachea upregulates expression of keratin 14 (K14) in basal cells. Consistent with this phenomenon, NTCU exposure showed a time-dependent increase in the number of K5/K14 dual-positive basal cells. To understand the mechanism by which NTCU treatment mediates ectopic expression of basal cells in the lung, we used flow-cytometry to analyze cell-surface markers expressed by tracheal basal cells. These studies revealed a time-dependent decrease in the level of integrin a6b4 (CD49f). CD49f is a hemidesmosomal protein that facilitates attachment of basal cells to the basement membrane. These findings suggested that NTCU treatment might promote migration of tracheal basal cells by destabilizing their adherence to the basement membrane.

      Conclusion
      Collectively, our results showed an early involvement of tracheal basal cells in the generation of dysplastic lung lesions in a murine model of SCC. By moving the focus proximal, we have discovered a realm of biological developments in the trachea that had not been previously examined. Further research of these processes will aid in the elucidation of dysplastic development in SCC.

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    P2.02 - Poster Session 2 - Novel Cancer Genes and Pathways (ID 148)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 2
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      P2.02-014 - Discovery of circulating protein biomarkers of lung dysplasia (ID 2481)

      13:11 - 13:28  |  Author(s): D.T. Merrick

      • Abstract

      Background
      Endobronchial dysplasia is a premalignant lesion commonly found in current and former smokers. Identifying and treating these lesions before they progress to lung cancer may improve survival. The iloprost chemoprevention trial demonstrated that supplementation with the prostacyclin analog, iloprost, reduced histologic dysplasia in former smokers (Keith et al. Cancer Prev Res. 2011). However, accurate detection of dysplasia requires invasive bronchoscopy to collect multiple endobronchial biopsy samples. This study is the first step in generating blood-based markers of dysplasia to identify individuals at high risk for developing lung cancer and who could benefit from chemoprevention treatment.

      Methods
      Baseline serum samples (n=70) collected from current and former smokers enrolled in the iloprost chemoprevention trial were analyzed with the SOMAscan proteomic platform, which measures 1129 proteins with a median limit of detection of 40 fM and 5% CV. To characterize dysplasia, 6 standardized endobronchial sites, as well as any others that appeared suspicious by either white light or autofluorescence visualization, were biopsied from each study participant and scored by expert pathologists. Samples were stratified by worst biopsy score (Max) for proteomic analysis. Biomarkers correlating with Max pathology score were identified using principal component analysis (PCA), a multivariate technique to identify correlated variables, and the univariate, non-parametric Kolmogorov-Smirnov test (KS test). Serum proteins correlating with pulmonary function were also analyzed.

      Results
      Six proteins correlated with the progression of Max pathology. The change in serum level of these proteins ranged from 14-50% when comparing the lowest (n=16) and highest (n=39) Max pathology score groups. The proteins function in neoplastic progression, cell adhesion, inflammation and metabolic regulation. The protein with the most significant change (FDR correct p value = 0.05) regulates plasma clearance of steroid hormones. The serum protein most strongly correlated with lung function in our study was VEGFR2, which mediates VEGF induced endothelial proliferation and is known to be reduced in the lungs of smokers and patients with COPD and emphysema.

      Conclusion
      Our preliminary results of serum biomarkers associated with preneoplastic dysplasia warrant further study. If validated, this serum-based test to identify individuals who may benefit from chemopreventive intervention could impact lung cancer survival. This work was supported by NCI grants CA 58187 and CA165780.

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      P2.02-015 - Proteomic insights with lung cancer tumors based on histopathologic subtypes and genotypes (ID 2467)

      13:28 - 13:45  |  Author(s): D.T. Merrick

      • Abstract

      Background
      Proteomic analysis of blood and tissue can reveal essential connections between the biochemical pathways altered in malignancy and tools for cancer diagnosis and treatment. The two major histologic subtypes of non-small cell lung cancer (NSCLC), adenocarcinoma (AD) and squamous cell carcinoma (SQ) differ in prognosis and optimal treatment. Targeting molecular pathways that drive malignancy has led to a paradigm shift in the development of specific treatments for patients based on their tumor mutation profile. We have conducted a comparative proteomic analysis of lung tumor histologic and driver mutation subsets to reveal biomarkers that link critical pathways for cell growth and survival to specific tumor phenotypes and genotypes.

      Methods
      We analyzed 68 NSCLC tumor and matched non-tumor tissue lysates (2 ug total protein/sample) with the SOMAscan proteomic platform, which measures 1129 proteins with a median limit of detection of 40 fM and 5% CV. The study consisted of 49 AD and 19 SQ tumors, 88% of which were Stage I or II. Somatic driver mutations were identified with multiplex PCR (SnapShot genotyping). Pairwise proteomic comparisons of tumor/non-tumor or AD/SQ tissue samples were performed using the Mann-Whitney test. The non-parametric Kruskal-Wallis test was used to discover differences among multiple pairwise driver mutation comparisons. Dependency network analysis was used to explore correlations enriched in tumor tissue vs non-tumor tissue. The statistical significance of the results was adjusted for multiple comparisons using false discovery rate (FDR) correction.

      Results
      Differences between tumor and non-tumor tissue were dominated by inflammatory, apoptotic and cell proliferation proteins. A total of 79 proteins were significantly different between AD and SQ at a 15% FDR. When compared to non-tumor levels, these proteins divided into 3 phenotypes: AD only (9 proteins), SQ only (19 proteins) or Both (51 proteins). Both refers to proteins that are tumor biomarkers in both AD and SQ and the protein levels are different between AD and SQ. The most common pattern was a progression in protein levels from non-tumor to AD to SQ, whether the pattern was higher or lower in tumor tissue. These proteins are members of cell proliferation and inflammatory pathways. This observation is consistent with the SQ only proteins, which are enriched for angiogenesis, cell proliferation and cell adhesion proteins. Driver mutation analysis revealed 5 inflammatory proteins that were higher in KRAS vs EGFR mutations and a TNF-alpha antagonist that was suppressed in EGFR mutants.

      Conclusion
      Unexpected findings that the AD proteome is closer to non-tumor lung tissue than SQ were revealed through broad proteomic profiling. Alteration in cell proliferation and inflammation pathways discovered in this study may lead to new insights in tumor biology and targeted therapeutics. This work was supported by a grant from the LUNGevity Foundation, NCI grant CA 58187 and Cancer Center Support Grant (P30CA046934).

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    P2.03 - Poster Session 2 - Technology and Novel Development (ID 151)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P2.03-007 - Changes in pulmonary immune cell recruitment and function during cigarette smoke-induced lung carcinogenesis in mice (ID 3370)

      09:30 - 09:30  |  Author(s): D.T. Merrick

      • Abstract

      Background
      Smoking-mediated lung cancer will cause at least 134,000 deaths in the USA this year. Even when detected at the earliest stages (stage IA and IB), five year survival is just slightly more than 50%. Chronic pulmonary inflammation is an established risk factor for lung cancer. Increased lung tumor macrophage infiltration is associated with poor prognosis, and murine lung tumor models exhibit increased macrophage infiltration. We hypothesize that chronic cigarette smoke exposure causes changes in inflammatory cell numbers and phenotypes creating a permissive environment for tumor formation. Chemopreventive agents such as the prostacyclin analog iloprost, may mitigate these changes.

      Methods
      FVB mice were given control AIN-76A chow or AIN-76A with 0.015% pioglitazone two weeks prior to smoke exposure. Mice were exposed to 70-90 mg/m[3] particulate level cigarette smoke for 6 hours/day, 5 days/week. Lungs were harvested 1 and 22 weeks after smoke exposure and after 22 weeks smoke/20 weeks ambient air (standard protocol for tumor induction). Bronchoalveolar cells were collected for qRT-PCR analysis of macrophage markers. Tumors were harvested and dissected from uninvolved tissue. Uninvolved lung tissue was digested and immune cell content analyzed by flow cytometry.

      Results
      Cigarette smoke exposure induced changes in macrophage phenotype after 1 week as indicated by CD11b exression (flow cytometry) and phenotypic markers (qRT-PCR). Macrophage infiltration increased in 22 week smoke/20 week ambient air exposed mice. Neutrophil numbers were increased at one week of smoke exposure. CD4 and CD8 positive T cell numbers decreased during smoke exposure but returned to control levels after smoking cessation. Smoke exposure differentially affected macrophage programming at each time point.

      Conclusion
      Cigarette smoke exposure affects pulmonary inflammatory cell numbers and function as early as 1 week after smoking initiation. Some of these changes are transient (increases in neutrophil numbers), while others are consistent but return to normal after smoking cessation (decreases in T cell populations). Smoke exposure resulted in early functional effects on macrophages and alveolar macrophage infiltration was still increased 20 weeks after smoking cessation, indicating that the effects of cigarette smoking on innate immunity are long lasting.