Mechanisms of ATF3-induced mammary tumorigenesis

项目摘要：ATF3是一种高度保守的转录因子，在 哺乳动物对DNA损伤的反应。初步数据显示，ATF3在两种情况下都显著上调 在许多人类乳腺肿瘤中的mRNA和蛋白水平。ATF3在角蛋白5表达中的过表达 BK5.ATF3转基因小鼠，包括乳腺肌上皮细胞，导致高 过表达p-连环素、K5、K6和K8的乳腺癌的发生率，类似于由 Wnt/p-catenin途径的遗传改变。推测ATF3的致癌作用 在这个模型中的表达涉及Wnt/p-catenin信号通路的上调，实验是 提出用来检验这一假说。在特定目标1中，TOPGAL报告基因将用于确定 Wnt/p-catenin信号在BK5.ATF3转基因小鼠乳腺肿瘤中是否活跃。这些 肿瘤还将在mRNA水平上表征为激活Wnt/p-catenin等重要基因 信号通路。在特定目标2中，癌前病变、化生性病变发生在未成熟乳腺。 BK5-ATF3转基因小鼠也将接受分子检测，以寻找Wnt/p-catenin途径是 使用相同的技术进行了升级。激光捕获冰冻切片的显微解剖将用于 分离病变组织以制备RNA。在特定目标3中，将发展转基因小鼠，在其中Wnt/p- 表达K5的细胞中的连环蛋白信号可以有条件地被消除。这种基因改变将是 联合BK5.ATF3转基因对两种鳞状上皮化生发生的影响 病变和腺鳞癌将被确定。在具体目标4中，推定的 将对野生型和转基因小鼠的腺体中的干细胞/祖细胞种群进行分析。的影响 在ATF3诱导下，Wnt/p-catenin诱导的乳腺肿瘤所必需的SDD基因的丢失 肿瘤的发生将被确定。这些研究的结果有望为 将ATF3与Wnt/p-catenin信号联系起来的机制，并为 环境致癌物与人类肿瘤发生的关系。这将建立ATF3的相关性 与已知与Wnt信号有关的几种肿瘤类型，特别是与基底样人乳房有关 肿瘤，一个预后较差且表型与ATF3诱导的小鼠乳腺肿瘤相似的亚群。 相关性：每9名美国女性中就有1人罹患乳腺癌。在这些癌症中，只有大约10%被解释 由遗传的癌症基因所致；其余的可能是由于暴露于损害DMA的环境因素和 遗传易感因素。已知的ATF3在DNA损伤反应中的重要性以及 在目前的模型中，ATF3的致癌特性可能提供了环境和环境之间的机制联系 暴露与人类乳腺癌易感性，特别是对预后较差的基底细胞样瘤。

Project Summary: ATF3 is a highly conserved transcription factor that is ubiquitously upregulated in the mammalian response to DNA damage. Preliminary data shows that ATF3 is significantly upregulated at both the mRNA and protein levels in many human breast tumors. Overexpression of ATF3 in keratin 5-expressing cells of BK5.ATF3 transgenic mice, including myoepithelial cells of the mammary gland, results in a high incidence of mammary carcinomas that overexpress p-catenin, K5, K6 and K8, similar to tumors induced by genetic alterations of the Wnt/p-catenin pathway. It is hypothesized that the oncogenic effects of ATF3 expression in this model involve upregulation of the Wnt/p-catenin signaling pathway, and experiments are proposed to test this hypothesis. In Specific Aim 1, the TOPGAL reporter gene will be used to determine whether Wnt/p-catenin signaling is active in mammary tumors arising in BK5.ATF3 transgenic mice. These tumors will also be characterized at the mRNA level for activation of the Wnt/p-catenin and other important signaling pathways. In Specific Aim 2, premalignant, metaplastic lesions arising in virgin mammary glands of BK5-ATF3 transgenic mice will also be examined molecularly for evidence that the Wnt/p-catenin pathway is upregulated, using the same techniques. Laser capture microdissection of frozen sections will be used to isolate the lesions for RNA preparation. In Specific Aim 3, transgenic mice will be developed in which Wnt/p- catenin signaling in K5-expressing cells can be conditionally eliminated. This genetic alteration will be combined with the BK5.ATF3 transgene and the effect on development of both squamous metaplastic lesions and adenosquamous carcinomas will be determined. In Specific Aim 4, the proportion of putative stem/progenitor cell populations in the glands of wild-type and transgenic mice will be assayed. The effect of loss of the Sdd gene, known to be required for Wnt/p-catenin-induced mammary tumors, on ATF3-induced tumorigenesis will be determined. The results of these studies are expected to provide clues to the mechanism that links ATF3 with Wnt/p-catenin signaling and to suggest new mechanisms for the involvement of environmental carcinogens with human tumorigenesis. This will establish relevance of ATF3 to several tumor types with known relationships to Wnt signaling, and particularly to basal-like human breast tumors, a subset with poor prognosis and phenotypic similarity to ATF3-induced mouse mammary tumors. Relevance: Breast cancer afflicts 1 in 9 American women. Only about 10% of these cancers are explained by inherited cancer genes; the rest are likely due to exposure to DMA-damaging environmental factors and genetic susceptibility factors. The known importance of ATF3 in the response to DNA damage and the oncogenic properties of ATF3 in the current model may provide a mechanistic link between environmental exposures and human breast cancer susceptibility, especially for basal-like tumors with poor prognosis.