Cancer deaths account for nearly 10 million deaths worldwide each year, with lung cancer (LCa) as the leading cause of cancer-related death. Smoking is one of the major LCa risk factors, and tobacco-related carcinogens are potent mutagens and epi-mutagens. In the present study, we aimed to analyse smoking-related epigenetic changes in lung tissues from LCa cases. The study cohort consisted of paired LCa and noncancerous lung tissues (NLT) from 104 patients, 90 of whom were smokers or ex-smokers (i.e. ever smokers) at the time of diagnosis. DNA methylation status of tumour suppressor genes DAPK1, MGMT, p16, RASSF1 and RARB was screened by means of methylation-specific PCR (MSP) and further analysed quantitatively by pyrosequencing. Methylation of at least one gene was detected in 59% (61 of 104) of LCa samples and in 39% (41 of 104) of NLT. DAPK1 and RASSF1 were more frequently methylated in LCa than in NLT (P = 0.022 and P = 0.041, respectively). The levels of DNA methylation were higher in LCa than NLT at most of the analysed CpG positions. More frequent methylation of at least one gene was observed in LCa samples of ever smokers (63%, 57 of 90) as compared with never smokers (36%, 5 of 14; P = 0.019). In the ever smokers group, methylation of the genes also occurred in NLT, but was rare or absent in the samples of never smokers. Among the current smokers, RASSF1 methylation in LCa showed association with the number of cigarettes smoked per day (P = 0.017), whereas in NLT it was positively associated with the duration of smoking (P = 0.039). Similarly, p16 methylation in LCa of current smokers correlated with the larger number of cigarettes smoked per day (P = 0.047). Overall, DNA methylation changes were present in both cancerous and noncancerous tissues of LCa patients and showed associations with smoking-related parameters.

中文翻译：

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患有非小细胞肺癌的吸烟者的癌性和非癌性肺组织中频繁出现 DNA 甲基化变化。


全球每年有近 1000 万人因癌症死亡，其中肺癌 (LCa) 是癌症相关死亡的主要原因。吸烟是主要的 LCa 危险因素之一，与烟草相关的致癌物是强效诱变剂和表观诱变剂。在本研究中，我们旨在分析 LCa 病例肺组织中与吸烟相关的表观遗传变化。该研究队列由来自 104 名患者的配对 LCa 和非癌性肺组织 (NLT) 组成，其中 90 名患者在诊断时为吸烟者或戒烟者（即曾经吸烟者）。通过甲基化特异性PCR（MSP）筛选抑癌基因DAPK1 、 MGMT 、 p16 、 RASSF1和RARB的DNA甲基化状态，并通过焦磷酸测序进一步定量分析。在 59%（104 个中的 61 个）的 LCa 样本和 39%（104 个中的 41 个）的 NLT 中检测到至少一个基因的甲基化。 DAPK1和RASSF1在 LCa 中比在 NLT 中更频繁地甲基化（分别为P = 0.022 和P = 0.041）。在大多数分析的 CpG 位点上，LCa 中的 DNA 甲基化水平高于 NLT。与从不吸烟者（36%，14 人中的 5 人； P = 0.019）相比，曾吸烟者（90 人中的 57 人，63%）的 LCa 样本中至少观察到一种基因更频繁的甲基化。在曾经吸烟者组中，NLT 中也发生了基因甲基化，但在从不吸烟者样本中很少或不存在。在当前吸烟者中，LCa 中的RASSF1甲基化与每天吸烟的数量相关（ P = 0.017），而 NLT 中的 RASSF1 甲基化与吸烟持续时间呈正相关（ P = 0.039）。 同样，当前吸烟者 LCa 中的p16甲基化与每天吸烟数量较多相关（ P = 0.047）。总体而言，LCa 患者的癌组织和非癌组织中均存在 DNA 甲基化变化，并显示出与吸烟相关参数的相关性。