DNA Repair Capacity Assays for Lung Disease Risk Assessment

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Project Summary Lung cancer (LC) is the leading cancer-related cause of death and COPD is third among all cause mortality. There are approximately 70 million current and former cigarette smokers (SM) in the US, although only 15-20% and ~17% will be diagnosed with LC or COPD, respectively. Thus, differences in susceptibility have been proposed to play an important role in LC and COPD disease etiology that also differs between non- Hispanic white (NHW) and Hispanic ethnicity. Smoking is estimated to be the cause of 85% of LC deaths and strongly associated with COPD. Exposure to other environmental respiratory carcinogens that include radon, wood smoke, and particulate matter 2.5 µ (PM2.5) may interact with cigarette smoking or individually be carcinogenic. LC in never smokers (NS) is increasing with 15-20,000 cases annually in the US. Risk factors include environmental tobacco smoke (sidestream smoke is the major component), radon, wood smoke and PM2.5. Wood smoke and PM2.5 are also associated with risk for COPD and most recently electronic cigarettes have been shown to affect pulmonary function. All of these environmental exposures have commonality in their ability to induce DNA damage. Reduced DNA repair capacity (DRC) has been shown to be associated with LC largely through hospital-based case-control studies, but has not been rigorously studied for COPD. These studies used the host cell reactivation or the mutagen sensitivity assay in response to specific DNA damaging agents. A major goal for this RFA “Expanding Genome Integrity Assays to Population Studies” is to develop and/or evaluate the performance of high throughput, functional DNA repair assays in the context of assessing disease phenotype and pathogenesis in a population setting. Our approach to this charge is to evaluate three emerging high throughput DRC assays – Litron in vitro flow cytometry-based MN assay, Trevigen comet assay, and the Trevigen hOGG1 FLARETM comet assay. In addition, through collaboration with Dr. Nagel, the performance of his flow cytometric host cell reactivation assay (FM-HCR) that measures the ability of human cells to repair different types of damage within plasmids transfected into the cells will be assessed. We will take advantage of two established cohorts, the LSC and New Mexico LC cohort to evaluate these DRC assays for predicting LC risk in SM and NS (Aim 1) and COPD in SM (Aim 2) through the exposure of their PMCs to total particulate matter (TPM) from mainstream and sidestream cigarette smoke, wood smoke, electronic cigarette aerosol, and H2O2 (mimic for radon). Aim 3 will address the ability to use the PMCs as a surrogate for risk prediction for LC and COPD by comparing the three DRC assays and exposures in primary bronchial epithelial cells obtained by bronchoscopy and matched PMCs. In addition, the FM-HCR assay will study controls from aims 1 and 2 that show the largest difference in DRC in response to one or more of the exposures to determine if this assay can replicate that outcome. Whether one or more of the specific DNA repair pathways (e.g., base excision) are driving the differences in DRC will also be determined.