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O12 - Lung Cancer Biology II (ID 87)
- Event: WCLC 2013
- Type: Oral Abstract Session
- Track: Biology
- Presentations: 1
- Moderators:Y. Nakanishi, B. Solomon
- Coordinates: 10/29/2013, 10:30 - 12:00, Parkside 110 A+B, Level 1
O12.02 - Pathway Analysis of Gene Expression Profiles that Distinguish Persistent from Regressive Bronchial Dysplasia Indicate Synergistic Role for Polo-Like Kinase 1 (PLK1) and Epoxide Hydrolase 3 (EPHX3) in Malignant Progression. (ID 3334)
10:30 - 12:00 | Author(s): D.T. Merrick
160,000 Americans die from lung cancer annually and the prognosis for invasive lung cancer is poor. Prevention of cancer represents an approach with high potential for significant reduction in mortality. Bronchial dysplasia (BD) is a precursor lesion of squamous cell carcinoma (SCC) of the lung, and persistent BDs represent a high risk subset of these lesions. Genomic instability is an important process underlying malignant progression. Gene expression microarray analyses were used to identify potential mediators of genomic instability in persistent BD and study their activity in these high risk lesions. Two genes, PLK1, which abrogates G2-M checkpoint DNA damage repair, and EPHX3, which converts tobacco smoke derived pro-carcinogens to mutagens, were selected for further analysis.
Sixty-three frozen baseline biopsies were classified into persistent/progressive BD, regressive BD , progressive non-dysplasia and stable non-dysplasia groups according to the presence or absence of BD on follow-up biopsies. H&E staining was performed on frozen sections to confirm histology, and RNA was harvested for global gene expression microarray analysis. Intergroup comparisons employed ANOVA statistical analysis with a false discovery rate of 10% to identify differentially expressed genes associated with persistence and gene expression alterations related to baseline histology used Spearman correlation coefficient cutoff of r= +/- 0.5. A pathway analysis (Ingenuity) using the persistence related genelist was performed to identify active pathways associated with persistence of BD. Validational studies were performed by quantitative RT-PCR in cell lines established from persistent and regressive bronchial sites. Inhibitors of persistence associated enzymes were used in tissue culture based assays of cellular proliferation.
Gene expression analyses support the unique biological nature of persistent BD. Intergroup comparisons showed significant numbers of differentially expressed genes only in the comparisons of persistent BD with regressive BD (318 genes) or stable non-dysplasia (6254 genes). 831 genes showed differential expression associated with increasing baseline dysplastic grade regardless of outcome. While approximately half of these genes also differentiated persistent from regressive BD, the presence of numerous persistence related genes that are independent of histology further substantiates the unique high risk nature of persistent BD. A pathway analysis revealed “mitotic roles of PLKs” as having the most significant association with persistence. Quantitative RT-PCR using cultures of 8 persistent BD and 6 regressive BD validated increased expression in persistent BD of PLK1 (2.77X, p=0.002) and EPHX3 (2.36X, p=0.081). Using a classification of dysplastic specimens as high or low expressers of PLK1 and/or EPHX3 (high > mean), we found a significant direct relationship with increased level of outcome diagnosis score: low expression of both genes (2.58); high expression of only one gene (3.60); and high expression of both (5.06). The baseline diagnosis did not differ between groups. Culture of the SCC cell line H2009 with EPHX inhibitor revealed a non-significant trend toward decreased proliferation (80.4% vs untreated).
Gene expression data confirms the biologically distinct nature of persistent BD. PLK1 and EPHX3 overexpression demonstrate a cooperative effect in respect to increased outcome histology suggesting a potential role for these enzymes in persistence/progression of BD via promotion of genomic instability.
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