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Household air pollution (HAP) from indoor combustion of solid fuel is a global health burden that has been linked to multiple diseases including lung cancer. In Xuanwei, China, lung cancer rate for nonsmoking women is among the highest in the world and largely attributed to high levels of polycyclic aromatic hydrocarbons (PAHs) that are produced from combustion of smoky (bituminous) coal. Alu retroelements, repetitive mobile DNA sequences that can somatically multiply and promote genomic instability have been associated with risk of lung cancer and diesel engine exhaust exposure. We conducted analyses for 160 nonsmoking women in an exposure assessment study in Xuanwei, China with a repeat sample from 49 subjects. Quantitative PCR was used to measure Alu repeat copy number relative to albumin gene copy number (Alu/ALB ratio). Associations between clusters derived from predicted levels of 43 HAP constituents, 5-methylchrysene (5-MC), a PAH previously associated with lung cancer in Xuanwei and was selected a priori for analysis, and Alu repeats were analyzed using generalized estimating equations. A cluster of 31 PAHs reflecting current exposure was associated with increased Alu copy number (β:0.03 per standard deviation change; 95% confidence interval (CI):0.01,0.04; P-value=2E-04). One compound within this cluster, 5-MC, was also associated with increased Alu copy number (P-value=0.02). Our findings suggest that exposure to PAHs due to indoor smoky coal combustion may contribute to genomic instability. Additionally, our study provides further support for 5-MC as a prominent carcinogenic component of smoky coal emissions. Further studies are needed to replicate our findings.

Purpose: Telomere length plays an important role in the maintenance of chromosomal stability and in tumorigenesis. We hypothesized that telomere length in peripheral WBC DNA obtained from healthy individuals would be a predictor of future risk of developing non-Hodgkin lymphoma.Experimental Design: Using a new assay to measure relative telomere length, monochrome multiplex quantitative PCR, which strongly correlates with telomere length measured by Southern blot (Spearman r = 0.91, P < 0.0001) and has high precision (coefficient of variation = 7%), we compared telomere length in peripheral WBC DNA in 107 incident male non-Hodgkin lymphoma cases and 107 matched controls within the prospective Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort.Results: Median (10th, 90th percentile) telomere length was 1.10 (0.79, 1.43) in cases and 1.02 (0.78, 1.26) in controls (P = 0.0017, Wilcoxon sign test). There was a strong dose-response relationship between quartiles of telomere length and risk of non-Hodgkin lymphoma overall [odds ratios (95% confidence intervals) by quartile: 1.0; 1.1 (0.4-2.7); 1.8 (0.7-4.9); and 3.6 (1.4-8.9); P trend = 0.003], and this association was similar across the most common non-Hodgkin lymphoma subtypes present in this study.Conclusion: These results suggest that longer telomere length may be a potential predictor for future risk of non-Hodgkin lymphoma. (Clin Cancer Res 2009;15(23):7429–33)

Determinants of leukocyte telomere length among controls

CCR Translation for the Article from A Prospective Study of Telomere Length Measured by Monochrome Multiplex Quantitative PCR and Risk of Non-Hodgkin Lymphoma

Background: It has been hypothesized that genomic instability related to telomere dysfunction may contribute to carcinogenesis. There is some evidence from case–control studies suggesting that short leukocyte telomere length may be associated with an increased risk of renal cell carcinoma (RCC); however, this association has not been investigated prospectively.Methods: We conducted a nested case–control study (209 cases, 410 controls) of RCC risk in relation to prediagnostic leukocyte telomere length in the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. ORs and 95% confidence intervals (CI) were estimated using conditional logistic regression.Results: Leukocyte telomere length was not significantly associated with future risk of RCC (highest quartile vs. lowest: OR, 0.8; 95% CI, 0.5–1.5; Ptrend = 0.6). Analyses stratified by sex, age, and time from blood collection to RCC diagnosis were similarly null.Conclusions: The results of this study, to our knowledge the first prospective investigation of its kind, do not support an association between prediagnostic leukocyte telomere length and risk of RCC.Impact: In contrast to some earlier reports, our findings add to the evidence that leukocyte telomere length is not a biomarker of risk related to the etiology of RCC. Cancer Epidemiol Biomarkers Prev; 22(5); 997–1000. ©2013 AACR.

Household air pollution (HAP) from indoor combustion of solid fuel is a global health burden that has been linked to lung cancer. A striking example occurs in Xuanwei, China where the lung cancer rate for never smoking women is among the highest in the world and largely attributed to high levels of various toxic constituents, including polycyclic aromatic hydrocarbons (PAHs), a combustion product of smoky (bituminous) coal used for cooking and heating. Several air pollution constituents have been associated with epigenetic accelerated aging (EAA) derived from DNA methylation (DNAm)-based biomarkers that are highly correlated with biological processes underlying aging-related diseases. We aim to assess the association between HAP exposure and EAA in Xuanwei, China. We analyzed 106 never smoking women in an exposure assessment study in Xuanwei, China with a repeat DNA sample from 23 subjects. Household fuel type used for cooking and heating (smoky vs. smokeless coal) was collected using a questionnaire, and exposure models were used to predict levels of 43 individual HAP constituents for current and childhood exposure. Leukocyte DNAm was measured using Illumina EPIC array. EAA was derived for five clocks using the Horvath calculator and defined as the residuals resulting from regressing each clock on chronological age. We used generalized estimating equations to assess the associations between fuel type, clusters derived from predicted levels of HAP exposure, and ambient 5-methylchrysene (5-MC), a carcinogenic PAH previously associated with lung cancer in Xuanwei and selected a priori for analyses, as independent variables and EAA clocks as dependent variables, while accounting for repeated-measurements. We observed a significant increase in GrimAge EAA among smoky coal users compared to smokeless coal users for current (β=1.84 years (y), 95% confidence interval (CI): 0.59, 3.09, P-value=0.004) and childhood (β=4.14 y, 95% CI: 1.63, 6.64, P-value=0.001) exposures. We also observed a monotonic increase in GrimAge EAA for a cluster of 31 PAHs reflecting current exposure (β=0.77 y, 95% CI: 0.36, 1.19, P-value=3 × 10−4) and for a cluster of 33 PAHs reflecting childhood exposure (β=0.92 y, 95% CI: 0.40, 1.45, P-value=0.001). Ambient 5-MC, one of the constituents within the PAH clusters, was found to have an increasing monotonic relationship with GrimAge EAA for current (β=0.15 y, 95% CI: 0.05, 0.25, P-value=0.003) and childhood (β=0.30 y, 95% CI: 0.13, 0.47, P-value=4.7 × 10−4) exposures. Our findings suggest that exposure to PAH from indoor smoky coal combustion is associated with EAA, particularly for the GrimAge clock, a strong biomarker of mortality. This finding is consistent with our recent observation linking accelerated GrimAge to increased risk of lung cancer in a prospective study of never smoking women in China. Additionally, our study provides further support for 5-MC as a prominent carcinogenic component of smoky coal emissions. Citation Format: Batel Blechter, Andres Cardenas, Seraphina (Junming) Shi, Mohammad L. Rahman, Jason Y.Y. Wong, Wei Hu, George S. Downward, Lutzen Portengen, Richard Cawthon, H. Dean Hosgood, Jihua Li, Debra T. Silverman, Yunchao Huang, Roel Vermeulen, Nathaniel Rothman, Qing Lan. Smoky coal exposure is associated with epigenetic accelerated aging. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4219.

Prospective cohort and genome-wide association studies have found consistent associations between longer leukocyte telomere length (LTL) and increased lung cancer risk. These findings present a paradox in the traditional expectations of telomere dynamics in cancer development, as longer telomeres are generally considered to be reflective of less advanced age and greater genomic stability. We posited that longer LTL may reflect or lead to delayed cellular senescence allowing cells to accumulate genomic abnormalities that drive lung carcinogenesis. Furthermore, increased copy number of Alu retroelements, repetitive mobile DNA sequences that are approximately 300 base pairs in length, could also reflect genomic instability. We previously found that exposure to diesel exhaust, a known lung carcinogen, was associated with increased Alu copy number and suspect that increased Alu retrotransposition could influence lung carcinogenesis. However, the interrelationship between Alu retroelements, LTL, and lung cancer is unknown. Therefore, we investigated associations between Alu copy number, LTL, and lung cancer risk in the prospective Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. We conducted a nested case-control study of 410 confirmed incident lung cancer cases and 416 controls individually matched on age, sex, race/ethnicity, study center, and blood draw date. Quantitative PCR was used to measure Alu copy number and telomere length relative to albumin (Alb) copy number (Alu/Alb and T/S ratio, respectively) in pre-diagnostic leukocytes. Conditional logistic regression was used to estimate associations between quartiles (Q) of Alu/Alb ratio (reference=Q1) and lung cancer risk, adjusted for matching factors, smoking status and packyears, and LTL. Additionally, we dichotomized Alu/Alb ratio and LTL at their medians and created a cross-combination variable to assess combined effects. We found a positive dose-response relationship between Alu/Alb ratio and lung cancer risk (odds ratio (OR), 95% confidence intervals (CI): Q2: 1.34 (0.73, 2.48); Q3:1.89 (0.94, 3.84); Q4: 2.66 (1.03, 5.63); p-trendordinal=0.02). The association was apparent for lung adenocarcinoma (LUAD) (Q2: 1.32 (0.46, 3.77); Q3: 2.88 (0.90, 9.25); Q4: 5.07 (1.29, 19.87); p-trendordinal=0.02). We have previously reported that longer measured LTL was also associated with an increased risk of LUAD (Q4: 2.82 (1.16-6.85); p-trend=0.011). The combined effect of both a higher Alu/Alb ratio and longer LTL was 6.07 (1.75, 21.04; p=4.5x10-3) for LUAD compared with lower/shorter levels of both. Higher Alu copy number and longer LTL were associated with increased risk of lung cancer, especially LUAD. Our findings require replication. If confirmed, evaluation of Alu copy number and LTL in risk stratification and prediction analyses is warranted. Citation Format: Jason Yat-Yang Wong, Richard Cawthon, Wei Hu, Somayina Ezennia, Shahinaz Gadalla, Charles Breeze, Batel Blechter, Neal Freedman, Wen-Yi Huang, H. Dean Hosgood, Wei Jie Seow, Bryan Bassig, Mohammad Rahman, Richard Hayes, Nathaniel Rothman, Qing Lan. Alu retroelement copy number, leukocyte telomere length, and lung cancer risk in the prospective Prostate, Lung, Colorectal and Ovarian Cancer (PLCO) Screening Trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2251.