Bladder cancer, a common neoplasm, is primarily caused by tobacco smoking. Epigenetic alterations including DNA methylation have the potential to be used as prospective markers of increased risk, particularly in at-risk populations such as smokers. We aimed to investigate the potential of smoking-related white blood cell (WBC) methylation markers to contribute to an increase in bladder cancer risk prediction over classical questionnaire-based smoking metrics (i.e., duration, intensity, packyears) in a nested case–control study within the prospective prostate, lung, colorectal, and ovarian (PLCO) Cancer Screening Trial and the alpha-tocopherol, beta-carotene cancer (ATBC) Prevention Study (789 cases; 849 controls). We identified 200 differentially methylated sites associated with smoking status and 28 significantly associated (after correction for multiple testing) with bladder cancer risk among 2670 previously reported smoking-related cytosine–phosphate–guanines sites (CpGs). Similar patterns were observed across cohorts. Receiver operating characteristic (ROC) analyses indicated that cg05575921 (AHHR), the strongest smoking-related association we identified for bladder cancer risk, alone yielded similar predictive performance (AUC: 0.60) than classical smoking metrics (AUC: 0.59–0.62). Best prediction was achieved by including the first principal component (PC1) from the 200 smoking-related CpGs alongside smoking metrics (AUC: 0.63–0.65). Further, PC1 remained significantly associated with elevated bladder cancer risk after adjusting for smoking metrics. These findings suggest DNA methylation profiles reflect aspects of tobacco smoke exposure in addition to those captured by smoking duration, intensity and packyears, and/or individual susceptibility relevant to bladder cancer etiology, warranting further investigation.

膀胱癌是一种常见的肿瘤，主要是由吸烟引起的。包括 DNA 甲基化在内的表观遗传改变有可能被用作风险增加的前瞻性标记，特别是在吸烟者等高危人群中。我们的目的是在嵌套病例对照中研究与吸烟相关的白细胞（WBC）甲基化标记物与传统的基于问卷调查的吸烟指标（即持续时间、强度、包年）相比，有助于增加膀胱癌风险预测的潜力。前瞻性前列腺癌、肺癌、结直肠癌和卵巢癌 (PLCO) 癌症筛查试验和 α-生育酚、β-胡萝卜素癌症 (ATBC) 预防研究（789 例病例；849 例对照）中的研究。我们在之前报道的 2670 个与吸烟相关的胞嘧啶-磷酸-鸟嘌呤位点 (CpG) 中确定了 200 个与吸烟状况相关的差异甲基化位点，以及 28 个与膀胱癌风险显着相关（经过多次测试校正后）的位点。在不同队列中观察到类似的模式。受试者工作特征 (ROC) 分析表明，cg05575921 (AHHR) 是我们确定的与膀胱癌风险最强的吸烟相关关联，其单独产生的预测性能 (AUC: 0.60) 与经典吸烟指标 (AUC: 0.59–0.62) 相似。通过将 200 个与吸烟相关的 CpG 中的第一个主成分 (PC1) 与吸烟指标一起纳入（AUC：0.63–0.65），可以实现最佳预测。此外，在调整吸烟指标后，PC1 仍然与膀胱癌风险升高显着相关。 这些发现表明，DNA 甲基化谱除了反映吸烟持续时间、强度和吸烟年数和/或与膀胱癌病因相关的个体易感性之外，还反映了烟草烟雾暴露的各个方面，值得进一步研究。