Exome-seq analysis of human bronchial epithelial cells (HBEC3KT) cells pre and post treatment with DMSO (Control) or 10 µg/ml cigarette smoke condensate (CSC) for 15 months and tumor xenografts obtained with 15 month CSC treated cells expressing KRASV12. Homo sapiens

We define how chronic cigarette smoke-induced time-dependent epigenetic alterations can sensitize human bronchial epithelial cells (HBEC) for transformation by a single oncogene. The smoke-induced, chromatin changes include initial repressive polycomb marking of genes later manifesting abnormal DNA methylation by 10 months. At this time, cells manifest epithelial to mesenchymal changes, anchorage-independent growth and upregulated RAS/MAPK signaling with silencing of hyper-methylated genes normally inhibiting these pathways and which are associated with smoking related NSCLC. These cells, in the absence of any driver gene mutations, now transform by introducing a single KRAS mutation and form adeno-squamous lung carcinomas in mice. Thus, epigenetic abnormalities may prime for changing oncogene senescence to addiction for a single key oncogene involved in lung cancer initiation. Overall design: HBEC cells treated with DMSO (Control) or 10 µg/ml CSC for 15 months. Xenografts were obtained by subcutaneously injecting 15 month CSC treated cells expressing KRASV12 in NSG mice.

我们阐明了慢性香烟烟雾诱导的时间依赖性表观遗传改变，可使人支气管上皮细胞（human bronchial epithelial cells, HBEC）致敏，进而使其具备被单个癌基因转化的潜能。烟雾诱导的染色质改变包括：早期对相关基因实施抑制性多梳蛋白标记，此类基因会在处理至10个月时呈现异常DNA甲基化。此时，细胞出现上皮间质转化、非锚定依赖性生长以及RAS/MAPK信号通路上调；同时，正常情况下可抑制上述通路的高甲基化基因发生沉默，且这类基因与吸烟相关非小细胞肺癌（non-small cell lung cancer, NSCLC）紧密相关。在未携带任何驱动基因突变的前提下，此类细胞可通过引入单个KRAS突变发生转化，并在NSG小鼠体内形成腺鳞肺癌。由此表明，表观遗传异常或可起到预激活作用，将癌基因的衰老表型转化为肺癌发生中关键单一癌基因的成瘾依赖状态。整体实验设计：将人支气管上皮细胞经二甲基亚砜（dimethyl sulfoxide, DMSO，对照）或10 μg/ml香烟烟雾凝析物（cigarette smoke condensate, CSC）处理15个月；异种移植瘤模型通过向NSG小鼠皮下注射经15个月CSC处理且表达KRASV12的细胞构建获得。