Mechanisms in Perinatal Carcinogenesis

围产期致癌机制

基本信息

批准号：
8157172
负责人：
Lucy M Anderson
金额：
$ 70.88万
依托单位：
DIVISION OF BASIC SCIENCES - NCI
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/8157172
关键词：
Perinatal Carcinogenesis

项目摘要

Perinatal exposures may lead to increased risk of childhood cancers, as well as those later in life. Preconceptional parental, transplacental, and/or neonatal exposures may be involved. Studies with animal models are utilized to increase understanding of underlying cellular and molecular mechanisms. We have been focusing on transgenerational effects of exposures and experiences of male mice on tumorigenesis and other endpoints in offspring. A possible mechanism of paternal effects on childhood cancer is male-mediated transgenerational carcinogenesis. Exposure of male mice to chromium(III), an environmental/occupational metal, results in increased neoplasms and other lesions in the offspring. The nature of these changes suggested hormonal involvement, and we have discovered alterations in serum glucose, corticosterone, IGF1, and the thyroid hormone T3 in the offspring. It is also important to discover the molecular mechanism in the sperm, by which changes-in-gene-expression signals are passed to offspring. Use of representational difference analysis, bisulfite sequencing, and pyrosequencing has revealed hypomethylation in the spacer-promoter region of the ribosomal RNA (rRNA) gene in sperm from Cr(III)-treated males. Ribosomal RNA is implicated in both growth and cancer. To test whether paternally-mediated effects are inherited by offspring, we have examined the gene in embryos and in tissues of young adult offspring, including liver and lung. Extensive statistical analyses of large numbers of litters and of offspring are now almost completed, and some surprising and interesing results are clear. Acidic saline, used as a vehicle for the Cr(III), also has had transgenerational effects. Importantly, offspring body weights and liver weights have been significantly increased as a result of the paternal treatments. The potential significance of this for several human diseases in addition to cancer is obvious. At the molecular level in studies of rRNA, single nucleotide polymorphisms, including one in the spacer-promoter and four alleles in the main promoter of the rRNA gene, are involved. The ratio of the alleles for the main promoter was actually changed by exposure of the fathers, selectively in the offspring lungs. This suggests tissue-specific genomic effects, either selective allelic expansion or gene conversion. If confirmed it will be a qualitatively new finding. The nature of the allele in the main promoter correlated with degree of methylation at five CpG sites in the spacer-promoter, in a tissue specific way. Degree of methylation was significantly affected by the paternal chromium treatment, in male offspring lungs. Importantly, these relationships between gene polymorphisms and gene methylation at a distant regulatory site were significantly modulated by treatment of the fathers. Since both the chromium(III), and the acid saline vehicle administered as a control, had clear effects, we looked for general, stressor-type effects in the males. Both chemical treatments were found to be stressors of the fathers, causing changes in serum corticosterone, insulin, leptin and glucose. Currently we are finding that these types of molecular changes also carry over into the F2 offspring, fathered by F1 males, that is, the grandchildren of the exposed males. Changes in the rRNA gene, both methylation and gene variant frequency, are greater than in the F1 mice This is particularly interesting in view of human epidemiology showing that experiences of grandfathers, for example amount of food available to them during certain intervals of childhood, affects risk of disease in their grandsons. To confirm these findings with another model and to simplify the experimental paradigm, we explored ways of exposing male mice directly to the stress hormone corticosterone. Preliminary trials have indicated that a key parameter is the age of these males at weaning, with different results obtained if the mice are weaned at 14 vs 21 days. This observation points to perinatal stress having a lasting effect on adult responses, a phenomenon worth study in its own right. Most consistent results were obtained with male weaned at 21 days. With such males, corticosterone treatment has an apparent effect on baseline weight and weight gain in the offspring. Statistical analysis of this result is in progress

围产期接触可能会导致儿童期以及晚年罹患癌症的风险增加。可能涉及孕前父母、经胎盘和/或新生儿的暴露。利用动物模型研究来增进对潜在细胞和分子机制的理解。我们一直关注雄性小鼠的暴露和经历对后代肿瘤发生和其他终点的跨代影响。父亲对儿童癌症的影响的一个可能机制是男性介导的跨代致癌。雄性小鼠接触铬（III）（一种环境/职业金属）会导致后代肿瘤和其他病变增加。这些变化的本质表明与激素有关，我们发现后代的血清葡萄糖、皮质酮、IGF1 和甲状腺激素 T3 发生了变化。发现精子中基因表达信号变化传递给后代的分子机制也很重要。使用代表性差异分析、亚硫酸氢盐测序和焦磷酸测序揭示了经 Cr(III) 处理的男性精子中核糖体 RNA (rRNA) 基因的间隔启动子区域的低甲基化。核糖体 RNA 与生长和癌症有关。为了测试父系介导的效应是否会遗传给后代，我们检查了胚胎和年轻成年后代组织（包括肝脏和肺）中的基因。对大量幼崽和后代的广泛统计分析现已基本完成，一些令人惊讶和有趣的结果已经很明显。酸性盐水用作 Cr(III) 的载体，也具有跨代效应。重要的是，由于父亲的治疗，后代的体重和肝脏重量显着增加。除癌症外，这对于多种人类疾病的潜在意义是显而易见的。在rRNA研究的分子水平上，涉及单核苷酸多态性，包括rRNA基因间隔启动子中的一个和主启动子中的四个等位基因。主要启动子等位基因的比例实际上是通过父亲的暴露而改变的，选择性地在后代肺部。这表明组织特异性基因组效应，要么是选择性等位基因扩增，要么是基因转换。如果得到证实，这将是一个质的新发现。主启动子中等位基因的性质与间隔启动子中五个 CpG 位点的甲基化程度以组织特异性方式相关。雄性后代肺部的甲基化程度受到父系铬处理的显着影响。重要的是，基因多态性和远距离调控位点的基因甲基化之间的关系受到父亲治疗的显着调节。由于铬（III）和作为对照的酸性盐水载体均具有明显的效果，因此我们在男性中寻找一般的应激源型效果。研究发现，这两种化学治疗都会给父亲带来压力，导致血清皮质酮、胰岛素、瘦素和葡萄糖发生变化。目前，我们发现这些类型的分子变化也会遗传到 F1 雄性的 F2 后代中，即暴露的雄性的孙辈。 rRNA 基因的变化，包括甲基化和基因变异频率，均大于 F1 小鼠。鉴于人类流行病学表明祖父的经历（例如，他们在童年时期的某些时间间隔内可获得的食物量）会影响这一点，这一点特别有趣。孙子患病的风险。为了用另一个模型证实这些发现并简化实验范式，我们探索了将雄性小鼠直接暴露于应激激素皮质酮的方法。初步试验表明，一个关键参数是这些雄性小鼠断奶时的年龄，如果小鼠在 14 天和 21 天断奶，则会得到不同的结果。这一观察结果表明，围产期压力对成人反应具有持久影响，这种现象本身就值得研究。最一致的结果是在 21 天时断奶的雄性身上获得的。对于这些雄性，皮质酮治疗对后代的基线体重和体重增加有明显影响。该结果的统计分析正在进行中