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MINI 23 - Lung Cancer Risk: Genetic Susceptibility and Airway Biology (ID 135)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Screening and Early Detection
- Presentations: 1
MINI23.07 - The Airway Field of Injury Reflects Metabolic Changes Associated with the Presence of Lung Squamous Premalignant Lesions (ID 2251)
16:45 - 18:15 | Author(s): S. Mazzilli
Lung SCC arises in the epithelial layer of the bronchial airways and is preceded by the development of premalignant lesions (PMLs). The molecular events involved in the progression of PMLs to lung SCC are not clearly understood as not all PMLs that develop go on to form carcinoma. Our group is using high-throughput genomic techniques to characterize the process of premalignant progression by examining PMLs and non-lesion areas of individuals with PMLs (“field of injury”) to identify events that lead to the development of SCC. Pathway analysis revealed enrichment oxidative phosphorylation (OXPHOS) /respiratory electron transport among genes up-regulated in the airways of subjects with PMLs. OXPHOS is the most efficient metabolic pathway that generates energy in the form of ATP by utilizing the structures and enzymes of the mitochondria. OXPHOS is often elevated during epithelial tissue repair and is superseded by glycolysis in the development of cancer.
mRNA-Seq was conducted on cytologically normal airway epithelium collected from indviduals with (n=50) and without (n=25) PMLs. Linear modeling strategies were used to identify genes altered between subjects with and without PMLs (n=206 out of 13,900, genes at FDR<0.001). Pathway analysis by GSEA revealed enrichment (FDR<0.05) of oxidative phosphorylation (OXPHOS)/respiratory electron transport genes among genes up-regulated in subjects with PMLs. To validate these findings, we examined oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) in primary airway epithelial cells cultures from PMLs and non-lesion areas and cancer cell lines that have high OXPHOS/ moderate glycolytic (H1299), moderate OXPHOS/ high glycolytic (HCC4006) or low OXPHOS/ low glycolytic (H2085) gene expression. In addition, protein expression of genes elevated in the field of injury including, translocase of the outer mitochondrial membrane (TOMM 22) and cytochrome C oxidase (COX-IV) were measured in FFPE sections of human PMLs and PMLs from the N-nitroso-tris-chloroethylurea (NTCU) mouse model of lung SCC.
OCR and ECAR values in the lung cancer cell lines were consistent with gene expression patterns. Perturbations of OXPHOS resulted in 3 fold (H1299) and 2 fold (HCC4006) higher OCR vales than those in H2085 cells (p<0.05) reflecting higher OXPHOS activity. Whereas the ECAR values were 2.5 fold (HCC4006) and 1.5 fold (H1299) higher than those in H2085 cells (p<0.05), reflecting higher glycolytic metabolism. The OCR and ECAR patterns in the primary premalignant cultures also supported the computational findings in the field of injury of PMLs. The baseline OCR/ECAR values were 1.5 fold higher in the cultures from PMLs compared to non-lesions controls (p<0.001). Additionally the OCR and ECAR values were elevated in response to perturbations in OXPHOS in the PMLs compared to controls. Protein levels of TOMM 22, and COX-IV were found to be elevated in dysplastic lesions compared to controls.
Together these data suggest that metabolism-associated gene expression is correlated with cellular metabolism and there is an increase in OXPHOS associated with the development of PMLs. Furthermore, there is potential that therapeutically increasing or maintaining OXPHOS in premalignant lesions or the field of injury may be a mechanism of prevention for lung cancer.
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