Mechanisms of Inorganic Carcinogenesis

无机致癌机制

基本信息

批准号：
7732881
负责人：
MICHAEL WAALKES
金额：
$ 178.63万
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/7732881
关键词：
Acute Adrenal Glands Adult All Sites Androgen Receptor Androgens Animals Apoptotic Arsenic Binding Biological Models Bladder Cadmium Cancer Model Cancer Patient Carcinogens Carrier Proteins Cell Line Cell model Cells Clinical Complement component C1s Cystathionine beta-Synthase DNA DNA Methylation Development Diethylstilbestrol Disease Disruption Dissection Dose Ductal Epithelial Cell Early identification Environment Epigenetic Process Epithelial Cells Estrogen Receptor alpha Estrogens Event Exposure to Gene Expression Genes Genetic Genitourinary system Genomics Glutathione Glutathione Metabolism Pathway Goals Health Hazards Homocysteine Homocystine Human Human Cell Line Hydrolase In Vitro Individual Intervention Kidney Kidney Neoplasms Knowledge Lead Lesion Life Liver Lung Malignant - descriptor Malignant Neoplasms Malignant neoplasm of kidney Malignant neoplasm of pancreas Malignant neoplasm of prostate Metabolism Metal exposure Metallothionein Metals Methionine Methylation Methyltransferase Modeling Molecular Molecular Target Mus Nature Occupational Exposure Organ Ovary Pancreas Pathway interactions Perinatal Exposure Physiological Poisoning Population Predisposing Factor Prevention Process Production Prostate Prostatic Proteins Public Health Reaction Recording of previous events Renal carcinoma Resistance Risk Rodent Model Role Signal Transduction Site Skin Skin Cancer Staging Stem cells Testing Time Tissue Sample Tissues Toxic effect Uterine Cancer Uterus Vagina Work carcinogenesis carcinogenicity cell transformation design drinking water exposed human population fetal hazard human data human study human tissue imprint in utero in vivo Model keratinocyte malignant phenotype methionine adenosyltransferase methyl group outcome forecast ovarian neoplasm pollutant postnatal prenatal prevent promoter response tumor tumor initiation xenoestrogen

项目摘要

Many inorganics are human carcinogens and pose major hazards to after environmental or occupational exposure. Arsenic and cadmium are two of the most important inorganic carcinogens and with arsenic alone over 100 million people world-wide are exposed to clearly unhealthy levels via contaminated drinking water in what is likely the worst mass poisoning in human history. Defining carcinogenic mechanisms will greatly aid in designing prevention or intervention strategies and in assigning appropriate levels of risk to these exposures. The primary goal of the ICS is to define the molecular mechanisms of carcinogenic action of arsenic and cadmium under the project titled Molecular Mechanisms of Inorganic Carcinogenesis. Since they can impact carcinogenicity and potentially provide a means for prevention or intervention, mechanisms of adaptation and acquired tolerance are studied as well. Emphasis is placed on key factors that dictate sensitivity, such as early-life exposure and poor expression of critical adaptive genes. These inorganics attack various targets sites in humans. Arsenic causes skin, urinary bladder, lung, kidney, liver, and prostatic malignancies and likely uterine cancers. Cadmium is primarily associated with human lung, prostatic and kidney cancers and recently pancreatic cancers. All these sites may have distinct differences in mode of action and adaption. Thus, various in vitro and in vivo model systems have been developed to study important molecular targets in targets tissues, with an emphasis on human relevance. These inorganic carcinogens likely have multiple mechanisms that are site and cell specific. A reproducible rodent model where inorganic arsenic acts a complete carcinogen has been developed in which brief in utero arsenic exposure in mice leads to tumors or proliferative lesions of the urogenital system, liver, lung and adrenal in the offspring as adults. The urogenital system lesions include transplacental arsenic-induced or initiated tumors of the ovaries, uterus, vagina, and bladder and proliferative lesions of the kidney. These results are in accord with human studies that indicate the liver, urinary bladder, lung, kidney and uterus are target tissues of arsenic carcinogenesis. Molecular mechanism studies indicate disruption of estrogen signaling by in utero exposure to arsenic contributes to the liver, lung and urogenital system malignancies, in part through aberrant activation of estrogen receptor-alpha. Indeed, we find that tumors and proliferative lesions of the urogenital system, including the uterus, ovary, vagina and urinary bladder, are greatly enhanced by postnatal exposure to synthetic estrogens like diethylstilbestrol. We also find evidence of aberrant estrogen signaling in arsenic exposed human liver. Further molecular characterization of arsenic-induced in utero tumor initiation is underway, including aberrant gene imprinting, using this model of arsenic carcinogenesis. We hypothesize that arsenic in utero may attack a critical pool of stem cells in target organs and induces aberrant genetic reprograming as part of its carcinogenic mechanism. These studies have important public health implications, including the identification of early life period as a time of very high sensitivity to arsenic. Human data is now emerging that fetal and/or early life exposure to arsenic is clearly carcinogenic. Further study will include prenatal arsenic exposure combined with exposures to urinary bladder and renal tumor promoters in mice to enhance the carcinogenic response to arsenic in these key human target organs. Various in vitro cell transformation model systems have also been developed to study inorganic carcinogenesis. In doing these studies we select cells with relevance to the human targets of arsenic, cadmium or lead carcinogenesis, and use low-level exposures for long periods, which approximates typical human exposures and avoids supra-physiological responses associated with acute high doses that could have limited relevance to the carcinogenic process. A human prostate epithelial cell line has been malignantly transformed with cadmium and arsenic, both potential human prostatic carcinogens. Additional work indicates the arsenic and cadmium transformants both acquire androgen independence, an event associated with a very poor clinical prognosis in prostatic cancer patients, largely through androgen receptor by-pass related mechanisms. Molecular dissection of the events associated with arsenic- or cadmium-induced malignant transformation in this and other human cell lines will continue with a focus of aberrant expression of genes critical to the carcinogenic process. In addition, a human prostate stem cell line has been developed and will be studied as a potential target cell population of these carcinogenic inorganics, and it clearly shows a survival selection advantage, a tleast for arsenic, along its was to malignant transformation. Furthermore, we have successfully transformed a human pancreatic ductal cell with cadmium, which fortifies a possible role of cadmium in this deadly disease. Similarly, arsenic has induced malignant transformation of human skin keratinocytes. The study of this arsenic-induced skin cancer model indicates that it occurs through a very different mechanism from internal cancers, one which involves apoptotic by-pass and aberrant survival of damaged skin cells with a strong possibility of survival selection of skin stem cells. The latter is now being tested in various model systems. Many cell biomethylate arsenic using specific methyltransferases S-adenosylmethionine (SAM) as the methyl group donor, which could compete for cellular methyl groups used in other enzymatic methylation reactions, such as DNA methylation. Altered DNA methylation is a common epigenetic finding in cancer, but we also find a loss of DNA methylation in arsenic target cells that do not biomethylate the metalloid. In this regard, after protracted low level arsenic exposure, the normal human prostate epithelial cells acquires a malignant phenotype with DNA hypomethylation, indicative of disrupted methyl metabolism, and shows arsenic adaptation involving glutathione overproduction and enhanced arsenic efflux. Thus, the interplay between methyl and glutathione metabolism during this progressive arsenic adaptation was studied. Arsenic-treated cells showed a time-dependent increase in adaption to arsenic toxicity and a marked increase in homocysteine (Hcy) levels. A marked suppression of SAM levels occurred with decreased methionine adenosyltransferase 2A (converts methionine to SAM) expression and increased negative regulator methionine adenosyltransferase B, suggesting reduced conversion of Hcy to SAM. Consistent with Hcy overproduction, activity of S-adenosylhomocysteine hydrolase (converts S-adenosylhomocysteine to Hcy) was increased. Cystathionine beta-synthase, a key gene in the transsulfuration pathway, and various glutathione production genes were increased, resulting greatly increased glutathione. Arsenic efflux increased along with expression of ATP-binding cassette protein C1, which effluxes arsenic as a glutathione conjugate. Genomic DNA hypomethylation was observed with arsenic exposure, indicating that the disruption in methyl metabolism h [summary truncated at 7800 characters]

许多无机物是人类致癌物，在环境或职业接触后会造成重大危害。砷和镉是两种最重要的无机致癌物，仅砷一项，全世界就有超过 1 亿人通过受污染的饮用水接触到明显不健康的水平，这可能是人类历史上最严重的大规模中毒事件。定义致癌机制将极大地有助于设计预防或干预策略以及为这些暴露分配适当的风险水平。 ICS 的主要目标是在名为“无机致癌作用的分子机制”的项目下确定砷和镉致癌作用的分子机制。由于它们可以影响致癌性并可能提供预防或干预手段，因此还研究了适应和获得性耐受的机制。重点放在决定敏感性的关键因素上，例如生命早期的暴露和关键适应性基因的表达不良。这些无机物攻击人体的各个目标部位。砷会导致皮肤癌、膀胱癌、肺癌、肾癌、肝癌、前列腺癌以及可能的子宫癌。镉主要与人类肺癌、前列腺癌和肾癌以及最近的胰腺癌有关。所有这些位点在作用方式和适应方面可能有明显的差异。因此，已经开发了各种体外和体内模型系统来研究靶组织中的重要分子靶点，重点是人类相关性。这些无机致癌物可能具有多种特定部位和细胞的机制。已经开发出一种可重复的啮齿动物模型，其中无机砷完全致癌，在该模型中，小鼠在子宫内短暂接触砷会导致成年后代的泌尿生殖系统、肝脏、肺和肾上腺出现肿瘤或增殖性病变。泌尿生殖系统病变包括经胎盘砷诱发或引发的卵巢、子宫、阴道和膀胱肿瘤以及肾脏的增殖性病变。这些结果与人体研究一致，表明肝脏、膀胱、肺、肾和子宫是砷致癌的靶组织。分子机制研究表明，子宫内接触砷会破坏雌激素信号传导，从而导致肝脏、肺和泌尿生殖系统恶性肿瘤，部分原因是雌激素受体α的异常激活。事实上，我们发现泌尿生殖系统（包括子宫、卵巢、阴道和膀胱）的肿瘤和增殖性病变因产后接触己烯雌酚等合成雌激素而大大增强。我们还在砷暴露的人类肝脏中发现了异常雌激素信号的证据。砷诱导的子宫内肿瘤发生的进一步分子表征正在进行中，包括使用砷致癌模型的异常基因印记。我们假设子宫内的砷可能会攻击靶器官中关键的干细胞库，并诱导异常的基因重编程，作为其致癌机制的一部分。这些研究具有重要的公共卫生意义，包括确定生命早期是对砷非常敏感的时期。现在出现的人类数据表明，胎儿和/或生命早期接触砷显然会致癌。进一步的研究将包括产前砷暴露与小鼠膀胱和肾肿瘤促进剂的暴露相结合，以增强这些关键人类靶器官对砷的致癌反应。还开发了各种体外细胞转化模型系统来研究无机致癌作用。在进行这些研究时，我们选择与砷、镉或铅致癌作用的人类目标相关的细胞，并长期使用低水平暴露，这接近典型的人类暴露，并避免与急性高剂量相关的超生理反应，这些反应可能会导致与致癌过程的相关性有限。人类前列腺上皮细胞系已被镉和砷恶性转化，这两种物质都是潜在的人类前列腺致癌物。其他工作表明砷和镉转化体都获得了雄激素独立性，这一事件与前列腺癌患者的临床预后非常差相关，主要是通过雄激素受体旁路相关机制。对该人类细胞系和其他人类细胞系中与砷或镉诱导的恶性转化相关的事件的分子剖析将继续关注对致癌过程至关重要的基因的异常表达。此外，人类前列腺干细胞系已经开发出来，并将作为这些致癌无机物的潜在靶细胞群进行研究，它清楚地显示出生存选择优势，至少砷，以及其恶性转化的能力。此外，我们成功地用镉转化了人类胰腺导管细胞，这强化了镉在这种致命疾病中可能发挥的作用。同样，砷也会诱导人类皮肤角质形成细胞的恶性转化。对这种砷诱导的皮肤癌模型的研究表明，它的发生机制与内部癌症非常不同，其中涉及细胞凋亡旁路和受损皮肤细胞的异常存活，并且皮肤干细胞的存活选择可能性很大。后者目前正在各种模型系统中进行测试。许多细胞使用特定的甲基转移酶 S-腺苷甲硫氨酸 (SAM) 作为甲基供体对砷进行生物甲基化，这可以与其他酶促甲基化反应（例如 DNA 甲基化）中使用的细胞甲基竞争。 DNA 甲基化改变是癌症中常见的表观遗传学发现，但我们也发现砷靶细胞中 DNA 甲基化缺失，而砷靶细胞不会对类金属进行生物甲基化。在这方面，在长期低水平砷暴露后，正常人前列腺上皮细胞获得DNA低甲基化的恶性表型，表明甲基代谢被破坏，并表现出涉及谷胱甘肽过量产生和砷外流增强的砷适应。因此，研究了这种渐进的砷适应过程中甲基和谷胱甘肽代谢之间的相互作用。砷处理的细胞对砷毒性的适应能力呈时间依赖性增加，同型半胱氨酸（Hcy）水平显着增加。 SAM 水平明显受到抑制，蛋氨酸腺苷转移酶 2A（将蛋氨酸转化为 SAM）表达减少，负调节因子蛋氨酸腺苷转移酶 B 增加，表明 Hcy 向 SAM 的转化减少。与 Hcy 过量产生一致，S-腺苷高半胱氨酸水解酶（将 S-腺苷高半胱氨酸转化为 Hcy）的活性增加。转硫途径中的关键基因胱硫醚β-合酶和各种谷胱甘肽生产基因增加，导致谷胱甘肽大大增加。砷的流出随着 ATP 结合盒蛋白 C1 的表达而增加，C1 将砷作为谷胱甘肽缀合物流出。在砷暴露下观察到基因组 DNA 低甲基化，表明甲基代谢受到破坏 h [摘要截断为 7800 个字符]

项目成果

期刊论文数量（71）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Focal adhesion kinase as a potential target in arsenic toxicity.

粘着斑激酶作为砷毒性的潜在靶标。

DOI：
10.1093/toxsci/kfi111
发表时间：
2005
期刊：
Toxicological sciences : an official journal of the Society of Toxicology
影响因子：
0
作者：
Liu,Jie;Waalkes,Michael
通讯作者：
Waalkes,Michael

Evaluation of DNA damage in patients with arsenic poisoning: urinary 8-hydroxydeoxyguanine.

砷中毒患者DNA损伤评价：尿8-羟基脱氧鸟嘌呤。

DOI：
10.1016/j.taap.2003.10.021
发表时间：
2004
期刊：
Toxicology and applied pharmacology
影响因子：
3.8
作者：
Yamauchi,Hiroshi;Aminaka,Yoshito;Yoshida,Katsumi;Sun,Guifan;Pi,Jingbo;Waalkes,MichaelP
通讯作者：
Waalkes,MichaelP

Role of glutathione in dimethylarsinic acid-induced apoptosis.

谷胱甘肽在二甲基胂酸诱导的细胞凋亡中的作用。

DOI：
10.1016/j.taap.2003.10.015
发表时间：
2004
期刊：
Toxicology and applied pharmacology
影响因子：
3.8
作者：
Sakurai,Teruaki;Ochiai,Masayuki;Kojima,Chikara;Ohta,Takami;Sakurai,MasumiH;Takada,NaokoO;Qu,Wei;Waalkes,MichaelP;Fujiwara,Kitao
通讯作者：
Fujiwara,Kitao

Strain differences of cadmium-induced hepatotoxicity in Wistar-Imamichi and Fischer 344 rats: involvement of cadmium accumulation.

Wistar-Imamichi 和 Fischer 344 大鼠中镉诱导的肝毒性的菌株差异：与镉积累有关。

DOI：
10.1016/j.tox.2004.06.012
发表时间：
2004
期刊：
Toxicology
影响因子：
4.5
作者：
Shimada,Hideaki;Takamure,Yasutaka;Shimada,Akinori;Yasutake,Akira;Waalkes,MichaelP;Imamura,Yorishige
通讯作者：
Imamura,Yorishige

Studies on the mechanisms of arsenic-induced self tolerance developed in liver epithelial cells through continuous low-level arsenite exposure.