Survival Signaling After Genotoxic Insult

基因毒性损伤后控制细胞存活的关键信号的不适当激活/失活可导致 自主生长和肿瘤转化。遗传毒性损伤的最初结果是细胞周期 检查点阻滞，但遗传毒性也可能激活细胞凋亡或终末生长阻滞的细胞死亡途径。 细胞对遗传毒性损伤的生存反应可能会产生内在的死亡抵抗力;这种选择性生长 有利的是可以允许转化表型的出现。某些形式的六价铬[（Cr（VI）] 是已知的人类呼吸道致癌物，可用作有用的遗传毒性工具， 毒理学重要性我们的初步研究表明，蛋白酪氨酸的维持 磷酸化，这是与AKT激活，推翻铬诱导的生长停滞， 提高克隆存活率。已知组成性AKT活化在癌发生中起重要作用。 因此，本提案的总体目标是阐明介导细胞凋亡的协调信号事件。 基因毒性损伤后的命运决定和存活率。提出的双重总体假设 研究表明：1）在Cr（VI）基因毒性后，AKT活化使细胞命运的平衡向存活方向转移， 2）面对Cr（VI）基因毒性损伤时的AKT活化增加了基因组不稳定性。测试 这些假设，我们将采用分子，药理学和遗传学的方法，通过使用相关的模型， 人二倍体肺成纤维细胞（HLF）和人大气道上皮细胞（HLAE）的系统，并研究其在肺成纤维细胞（HLF）中的表达。 参与AKT通路的关键信号传导成分。AKT效应的分子电路将 在目标1中描述，AKT诱导的基因毒素“覆盖”的后果 将在目标2中研究细胞死亡程序。目的3将确定AKT在抗 在对Cr（VI）具有获得性抗性的亚克隆细胞群体中Cr（VI）诱导的克隆形成性致死性 诱导克隆性死亡。我们将使用可溶性Na 2CrO 4，其浓度范围与人体相关， 暴露，并为DNA加合物的频率和遗传毒性病变有据可查。结果 所提出的研究将确定分子机制，该机制赋予细胞生长优势， 遗传毒性损伤，并增加新的见解，以了解铬（VI）诱导的肺癌，而 解决了对可与暴露相关的敏感和特异性分子指数的需要， 致癌物质，以及它们的癌症发病率。分子电路的描绘 参与AKT存活信号传导的基因可能有额外的好处， 抗癌药物设计。

Inappropriate activation/inactivation of key signals that control cell survival after genotoxic insult can contribute to autonomous growth and neoplastic transformation. An initial consequence of genotoxic injury is cell cycle checkpoint arrest but genotoxicity may also activate cell death pathways of apoptosis or terminal growth arrest. Cellular survival responses to genotoxic insult may produce intrinsic death-resistance; such a selective growth advantage may allow for emergence of a transformed phenotype. Certain forms of hexavalent chromium [(Cr(VI)] are known human respiratory carcinogens that can be employed as useful genotoxic tools with relevant toxicological importance. Our preliminary studies suggest that maintenance of protein tyrosine phosphorylation, which is coincident with AKT activation, overrides Cr-induced growth arrest and enhances clonogenic survival. Constitutive AKT activation is known to play an important role in carcinogenesis. Therefore, the overall objective of this proposal is to elucidate the coordinate signaling events that mediate cell fate determination and survival after genotoxic insult. The dual overarching hypotheses of the proposed studies are that: 1) AKT activation shifts the balance of cell fates, toward survival, after Cr(Vl) genotoxic insult; and 2) AKT activation in the face of Cr(Vl) genotoxic insult increases genomic instability. To test these hypotheses, we will employ molecular, pharmacological and genetic approaches, by using relevant model systems of human diploid lung fibroblasts (HLF), and human large airway epithelial cells (HLAE) and studying the involvement of key signaling components of the AKT pathway. The molecular circuitry of the AKT effect will be delineated in Aim 1, and the consequences of an AKT-induced "override" of the genotoxin-elicited program of cell death will be investigated in Aim 2. Aim 3 will identify the role of AKT in resistance to Cr(Vl)-induced clonogenic lethality in a subclonal population of cells with acquired resistance to Cr- induced clonogenic death. We will use soluble Na2CrO4 at a range of concentrations relevant to human exposure, and for which the DNA adduct frequencies and genotoxic lesions are well documented. Results of the proposed studies will identify molecular mechanism(s) that confer a growth advantage to cells after genotoxic insult, and add new insights to the understanding of Cr(Vl)-induced lung carcinogenesis, while addressing a need for sensitive and specific molecular indices that can be correlated with exposure to carcinogenic agents, as well as with their cancer incidence. Delineation of the molecular circuitry involved in AKT survival signaling may have the added benefit of identifying molecular targets for rational drug design in anti-cancer therapy.