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Epigenetic clock as the new hand of time for lung cancer in never smokers
  1. David C Christiani
  1. Environmental Health, Harvard School of Public Health Aids Initiative, Boston, Massachusetts, USA
  1. Correspondence to Dr David C Christiani, Environmental Health, Harvard School of Public Health Aids Initiative, Boston, Massachusetts, USA; dchris{at}

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Estimates of lung cancer among persons who never smoked are 10%–20% in the USA, translating into 20–40 000 cases annually. Globally, and especially in East Asia, the incidence of lung cancer among non-tobacco users is considerably higher than in the USA, especially in women.1 The causes of lung cancer in lifelong never-smokers are not well understood. Possibilities include exposure to other carcinogens such as air pollution, radon, occupational exposures, secondhand tobacco smoke, genetic mutations, infections and hormonal imbalances. A mechanistic explanation may include epigenetic modifications from accumulated DNA damage as part of the ageing process. Some studies have shown that epigenetic age, or DNA methylation markers may be a better indicator of biological age than simple chronological age.2 3 Genes that are silenced, like the tumour suppressor gene p53, can lead to increased cancer risk.

DNA methylation, the addition of methyl groups to DNA mainly along sequences, results in silencing of gene expression. Hence, DNA methylation plays an important role in a variety of biological …

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  • Correction notice This article has been corrected since it was published Online First. The CpG site was listed incorrectly.

  • Funding This study was funded by US National Institutes of Health, National Cancer Center (U01 CA209414)

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.

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