ATF3, a stress-inducible gene, in tumorigenesis and metastasis

目的和假设：在癌症进展过程中，细胞会遇到许多应激信号。如果无法修复，细胞有内在的机制来消除自己。成功的癌细胞成功地挫败了这种固有的应激反应。事实上，癌细胞似乎可以选择一些肿瘤抑制因子成为癌基因。TGF¿是最著名的例子，展示了这种“化身”转换。ATF3是一种应激诱导基因，是一种调控基因，最近被发现在癌症进展中具有双重作用：它在未转化的乳腺上皮细胞中促凋亡，但保护恶性细胞免受应激并促进其转移。长期目标是了解癌症的二分法，使用ATF3作为处理这个问题的方法。本提案将重点研究ATF3在乳腺癌中的致癌作用。Aim 1将验证ATF3与TGF¿通路中的蛋白Smad3的相互作用在晚期乳腺癌细胞中ATF3的致癌活性中发挥重要作用的假设。这将通过结构-功能分析进行测试，包括域交换和位点定向诱变。Aim 2将验证ATF3在恶性细胞中发挥其致癌作用的假设，至少部分是通过调节下游靶基因。潜在的靶启动子将通过染色质免疫沉淀法和转录法进行检测，以确定它们是否是ATF3的直接靶基因。此外，ATF3对其调控的生物学意义也将被检验。目的3将验证ATF3在巨噬细胞-肿瘤相互作用中起重要作用的假设。使用体外共培养和体内脂肪垫注射模型，将采用功能获得和功能丧失两种方法来测试ATF3是否在癌细胞与巨噬细胞相互作用的能力中发挥作用。意义：ATF3是一种新的调控因子，在肿瘤进展中具有双重作用，并可能在间质癌相互作用中发挥作用。由于它是由抗癌药物诱导的，其致癌功能表明这些药物可能有不良作用。该方案提供的信息可能为抗癌治疗的合理设计提供线索，从而有可能改变未来的临床实践。公共卫生相关性：尽管在早期检测和治疗方面取得了巨大进步，但乳腺癌一旦转移到区域淋巴结以外就无法治愈。因此，为了对抗乳腺癌，有必要更好地了解它的转移。本研究旨在研究一种调控乳腺癌转移的主开关基因。

DESCRIPTION (provided by applicant): Goal and Hypothesis: During cancer progression, the cells encounter many stress signals. If beyond repair, the cells have built-in mechanisms to eliminate themselves. The successful cancer cells managed to foil this hardwired stress response. In fact, it appears that cancer cells can co-opt some tumor suppressors to become oncogenes. TGF¿ is the best-known example exhibiting this "Jekyll and Hyde" conversion. ATF3, a stress- inducible gene, is a regulatory gene that was recently identified to have a dichotomous role in cancer progression: it is pro-apoptotic in non-transformed breast epithelial cells, but protects the malignant cells from stress and promotes their metastasis. The long-term objective is to understand the cancer dichotomy using ATF3 as a handle to address this issue. This proposal will focus on the oncogenic aspect of ATF3 in breast cancer. Aim 1 will test the hypothesis that the interaction of ATF3 with Smad3, a protein in the TGF¿ pathway, plays an important role in the oncogenic activity of ATF3 in advanced breast cancer cells. This will be tested by structure-function analyses, including domain swap and site-directed mutagenesis. Aim 2 will test the hypothesis that ATF3 exerts its oncogenic action in malignant cells, at least in part, by regulating downstream target genes. Potential target promoters will be tested by chromatin immunoprecipitation assay and transcription assay to determine whether they are the direct target genes of ATF3. In addition, the biological significance of their regulation by ATF3 will be tested. Aim 3 will test the hypothesis that ATF3 is important for macrophage-cancer interaction. Both gain- and loss- of-function approaches, using in vitro co-culture and in vivo fat pad injection models, will be taken to test whether ATF3 plays a role in the ability of cancer cells to interact with macrophages. Significance: ATF3 is a new regulator that has a dichotomous role in cancer progression, and may play a role in stroma-cancer interaction. Because it is induced by anti-cancer drugs, its oncogenic function indicates that these drugs may have undesired effects. Information from the proposal may provide clues for rational designs of anti-cancer treatment, thus potentially changing the clinical practice in the future. PUBLIC HEALTH RELEVANCE: Despite the tremendous advances in early detections and treatments, breast cancer becomes incurable once metastasized beyond the regional lymph nodes. Thus, to combat breast cancer, it is essential to better understand its metastasis. This proposal investigates a master switch gene that regulates breast cancer metastasis.