Gene Promoter Hypermethylation Detected in Sputum Predicts FEV1 Decline and All-Cause Mortality in Smokers

Association of Lung Function Decline with All-Cause and Cancer-Cause Mortality after World Trade Center Dust Exposure

Rationale: In numerous cohorts, lung function decline is associated with all-cause and cardiovascular-cause mortality, but the association between the decrease in forced expiratory volume in 1 second (FEV1) and cancer-cause mortality, particularly after occupational/environmental exposure(s), is unclear. Exposure to dust/smoke from the World Trade Center (WTC) disaster caused inflammation and lung injury in Fire Department of the City of New York rescue/recovery workers. In addition, prior research found that >10% of the cohort experienced greater than twice the age-related decrease in FEV1 (⩾64 ml/yr). Objectives: To evaluate the association of longitudinal lung function with all-cause and cancer-cause mortality after exposure to the WTC disaster. Methods: We conducted a prospective cohort study using longitudinal prebronchodilator FEV1 data for 12,264 WTC-exposed firefighters and emergency medical service providers. All-cause and cancer-cause mortality were ascertained using National Death Index data from September 12, 2001, through December 31, 2021. Joint longitudinal survival models evaluated the association of baseline FEV1 and change in FEV1 from baseline with all-cause and cancer-cause mortality adjusted for age, race/ethnicity, height, smoking, work assignment (firefighters vs. emergency medical service providers), and WTC exposure. Results: By December 31, 2021, 607 of the 12,264 individuals in the cohort (4.9%) had died (crude rate = 259.5 per 100,000 person-years), and 190 of 12,264 (1.5%) had died from cancer (crude rate = 81.2 per 100,000 person-years). Baseline FEV1 was ⩾80% predicted in 10,970 of the 12,264 (89.4%); final FEV1 was ⩾80% in 9,996 (81.5%). Lower FEV1 at baseline was associated with greater risk for all-cause mortality (hazard ratio [HR] per liter = 2.32; 95% confidence interval [95% CI] = 1.98-2.72) and cancer-cause mortality (HR per liter = 1.99; 95% CI = 1.49-2.66). Longitudinally, each 100-ml/yr decrease in FEV1 was associated with an 11% increase in all-cause mortality (HR = 1.11; 95% CI = 1.06-1.15) and a 7% increase in cancer-cause mortality (HR = 1.07; 95% CI = 1.00-1.15). Compared with FEV1 decrease <64 ml/yr, those with FEV1 decrease ⩾64 ml/yr had higher all-cause (HR = 2.91; 95% CI = 2.37-3.56) and cancer-cause mortality (HR = 2.68; 95% CI = 1.90-3.79). Conclusions: Baseline FEV1 and longitudinal FEV1 decrease are associated with increased risk of all-cause and cancer-cause mortality in a previously healthy occupational cohort, the majority of whom had normal lung function, after intense exposure to dust/smoke. Further investigation is needed to define pathways by which lung function impacts mortality after an irritant exposure.

Wood smoke exposure affects lung aging, quality of life, and all-cause mortality in New Mexican smokers

Background

The role of wood smoke (WS) exposure in the etiology of chronic obstructive pulmonary disease (COPD), lung cancer (LC), and mortality remains elusive in adults from countries with low ambient levels of combustion-emitted particulate matter. This study aims to delineate the impact of WS exposure on lung health and mortality in adults age 40 and older who ever smoked.

Methods

We assessed health impact of self-reported “ever WS exposure for over a year” in the Lovelace Smokers Cohort using both objective measures (i.e., lung function decline, LC incidence, and deaths) and two health related quality-of-life questionnaires (i.e., lung disease-specific St. George's Respiratory Questionnaire [SGRQ] and the generic 36-item short-form health survey).

Results

Compared to subjects without WS exposure, subjects with WS exposure had a more rapid decline of FEV1 (− 4.3 ml/s, P = 0.025) and FEV1/FVC ratio (− 0.093%, P = 0.015), but not of FVC (− 2.4 ml, P = 0.30). Age modified the impacts of WS exposure on lung function decline. WS exposure impaired all health domains with the increase in SGRQ scores exceeding the minimal clinically important difference. WS exposure increased hazard for incidence of LC and death of all-cause, cardiopulmonary diseases, and cancers by > 50% and shortened the lifespan by 3.5 year. We found no evidence for differential misclassification or confounding from socioeconomic status for the health effects of WS exposure.

Conclusions

We identified epidemiological evidence supporting WS exposure as an independent etiological factor for the development of COPD through accelerating lung function decline in an obstructive pattern. Time-to-event analyses of LC incidence and cancer-specific mortality provide human evidence supporting the carcinogenicity of WS exposure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02162-y.

Blood leukocyte count as a systemic inflammatory biomarker associated with a more rapid spirometric decline in a large cohort of iron and steel industry workers

Objective

Iron and steel industry workers are exposed to high levels of inhalable dust particles that contain various elements, including metals, and cause occupational lung diseases. We aim to assess the relationship between occupational dust exposure, systemic inflammation, and spirometric decline in a cohort of Chinese iron and steel workers.

Methods

We studied 7513 workers who participated in a Health Surveillance program at Wugang Institute for Occupational Health between 2008 and 2017. Time-weighted exposure intensity (TWEI) of dust was quantified based on self-reported dust exposure history, the experience of occupational hygienists, and historical data of dust exposure for workers with certain job titles. A linear mixed-effects model was used for association analyses.

Results

The average annual change of lung function was − 50.78 ml/year in forced expiratory volume in 1 s (FEV1) and − 34.36 ml/year in forced vital capacity (FVC) in males, and − 39.06 ml/year in FEV1 and − 26.66 ml/year in FVC in females. Higher TWEI prior to baseline was associated with lower longitudinal measurements of FEV1 and FVC but not with their decline rates. Higher WBC and its differential at baseline were associated with lower longitudinal measurements and a more rapid decline of FEV1 and FVC in a dose-dependent monotonically increasing manner. Moreover, the increase of WBC and its differential post-baseline was also associated with a more rapid decline of FEV1 and FVC.

Conclusions

Our findings support the important role of systemic inflammation in affecting the temporal change of lung function in iron and steel industry workers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01849-y.

DNA Methylation Is Predictive of Mortality in Current and Former Smokers

Rationale: Smoking results in at least a decade lower life expectancy. Mortality among current smokers is two to three times as high as never smokers. DNA methylation is an epigenetic modification of the human genome that has been associated with both cigarette smoking and mortality.Objectives: We sought to identify DNA methylation marks in blood that are predictive of mortality in a subset of the COPDGene (Genetic Epidemiology of COPD) study, representing 101 deaths among 667 current and former smokers.Methods: We assayed genome-wide DNA methylation in non-Hispanic white smokers with and without chronic obstructive pulmonary disease (COPD) using blood samples from the COPDGene enrollment visit. We tested whether DNA methylation was associated with mortality in models adjusted for COPD status, age, sex, current smoking status, and pack-years of cigarette smoking. Replication was performed in a subset of 231 individuals from the ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints) study.Measurements and Main Results: We identified seven CpG sites associated with mortality (false discovery rate < 20%) that replicated in the ECLIPSE cohort (P < 0.05). None of these marks were associated with longitudinal lung function decline in survivors, smoking history, or current smoking status. However, differential methylation of two replicated PIK3CD (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta) sites were associated with lung function at enrollment (P < 0.05). We also observed associations between DNA methylation and gene expression for the PIK3CD sites.Conclusions: This study is the first to identify variable DNA methylation associated with all-cause mortality in smokers with and without COPD. Evaluating predictive epigenomic marks of smokers in peripheral blood may allow for targeted risk stratification and aid in delivery of future tailored therapeutic interventions.

Identification of novel epigenetic abnormalities as sputum biomarkers for lung cancer risk among smokers and COPD patients

OBJECTIVES

Smoking is a common risk factor for chronic obstructive pulmonary disease (COPD) and lung cancer. Although COPD patients have higher risk of lung cancer compared to non-COPD smokers, the molecular links between these diseases are not well-defined. This study aims to identify genes that are downregulated by cigarette smoke and commonly repressed in COPD and lung cancer.

MATERIALS AND METHODS

Primary human airway epithelial cells (HAEC) were exposed to cigarette-smoke-extract (CSE) for 10-weeks and significantly suppressed genes were identified by transcriptome array. Epigenetic abnormalities of these genes in lung adenocarcinoma (LUAD) from patients with or without COPD were determined using genome-wide and gene-specific assays and by in vitro treatment of cell lines with trichostatin-A or 5-aza-2-deoxycytidine.

RESULTS

The ten most commonly downregulated genes following chronic CSE exposure of HAEC and show promoter hypermethylation in LUAD were selected. Among these, expression of CCNA1, SNCA, and ZNF549 was significantly reduced in lung tissues from COPD compared with non-COPD cases while expression of CCNA1 and SNCA was further downregulated in tumors with COPD. The promoter regions of all three genes were hypermethylated in LUAD but not normal or COPD lungs. The reduced expression and aberrant promoter hypermethylation of these genes in LUAD were independently validated using data from the Cancer Genome Atlas project. Importantly, SNCA and ZNF549 methylation detected in sputum DNA from LUAD (52% and 38%) cases were more prevalent compared to cancer-free smokers (26% and 15%), respectively (p < 0.02).

CONCLUSIONS

Our data show that suppression of CCNA1, SNCA, and ZNF549 in lung cancer and COPD occurs with or without promoter hypermethylation, respectively. Detecting methylation of these and previously identified genes in sputum of cancer-free smokers may serve as non-invasive biomarkers for early detection of lung cancer among high risk smokers including COPD patients.

Potential Micronutrients and Phytochemicals against the Pathogenesis of Chronic Obstructive Pulmonary Disease and Lung Cancer

Lung cancer and chronic obstructive pulmonary disease have shared etiology, including key etiological changes (e.g., DNA damage and epigenetics change) and lung function impairment. Focusing on those shared targets may help in the prevention of both. Certain micronutrients (vitamins and minerals) and phytochemicals (carotenoids and phenols) have potent antioxidant or methyl-donating properties and thus have received considerable interest. We reviewed recent papers probing into the potential of nutrients with respect to lung function preservation and prevention of lung cancer risk, and suggest several hypothetical intervention patterns. Intakes of vitamins (i.e., A, C, D, E, B₁₂), carotenoids, flavonoids, curcumins, resveratrol, magnesium, and omega-3 fatty acids all show protective effects against lung function loss, some mainly by improving average lung function and others through reducing decline rate. Dietary interventions early in life may help lung function reserve over the lifespan. Protective nutrient interventions among smokers are likely to mitigate the effects of cigarettes on lung health. We also discuss their underlying mechanisms and some possible causes for the inconsistent results in observational studies and supplementation trials. The role of the lung microbiome on lung health and its potential utility in identifying protective nutrients are discussed as well. More prospective cohorts and well-designed clinical trials are needed to promote the transition of individualized nutrient interventions into health policy.