癌基因和/或肿瘤抑制基因（TSGs）的异常表达推动着甲状腺癌的发生和发展。我们研究了启动转录因子（ATF）/CREB转录因子（TF）家族的一个成员ATF3在甲状腺癌中的表达和功能。我们利用中山大学附属第一医院的80名乳头状甲状腺癌（PTC）患者以及510个PTC样本的癌基因组图谱甲状腺癌数据库进行基因表达和预后分析。生存数据通过Kaplan-Meier曲线和Cox回归进行分析，考虑了年龄、性别、多发性、颈外扩展、淋巴结转移和新辅助治疗史的调整。DNA甲基化通过甲基化特异性PCR和亚硫酸盐测序PCR进行分析。通过DNA下拉结合质谱分析鉴定与ATF3启动子结合的转录因子，并通过定量PCR（qPCR）、荧光素酶报告基因实验和染色质免疫沉淀（ChIP）-qPCR进行确认。我们在体外和异种移植小鼠模型中进行功能实验，评估了ATF3在甲状腺癌中的功能。基于RNA测序、ChIP-seq和CUT&Tag测序的综合分析用于探索ATF3功能的机制。ATF3在PTC中显著下调，ATF3表达低的患者进展无病生存期减少（调整风险比=0.50，95% CI：0.26-0.98，P=0.043）。ATF3启动子的DNA高甲基化破坏了SP1和MYC-MAX的结合，导致基因的失活。ATF3通过抑制甲状腺癌细胞的增殖和迁移发挥了肿瘤抑制基因的作用。并且ATF3通过结合这些基因的调控元件，特别是MAPK和PI3K/AKT通路基因，调节了多个基因的表达。在这些靶基因中，FLNC受ATF3的正调控，并且与甲状腺癌更有利的预后有关，而DUSP10、FN1、TNC和CREB5受ATF3的负调控，并与较差的预后有关。我们观察到启动子DNA高甲基化降低了ATF3的表达，进而通过直接调控MAPK和PI3K/AKT通路中与预后相关的基因，至少部分地促进了甲状腺癌的进展。

Aberrant expression of oncogenes and/or tumor suppressor genes (TSGs) drives the tumorigenesis and development of thyroid cancer. We investigated the expression and function of a member of the activating transcription factor (ATF)/CREB transcription factor (TF) family, ATF3, in thyroid cancer.Data from eighty patients with papillary thyroid cancer (PTC) in the First Affiliated Hospital of Sun Yat-sen University and 510 PTC samples in The Cancer Genome Atlas thyroid cancer database were utilized for gene expression and prognosis analyses. The survival data were analyzed by Kaplan-Meier curves and Cox regression with adjustment for age, sex, multilocality, extrathyroidal extension, lymph metastases and history of neoadjuvant treatment. DNA methylation was analyzed by methylation specific PCR and bisulfite sequencing PCR. TFs binding to ATF3 promoter were identified by DNA pull-down combined with mass spectrum assay, and confirmed by quantitative PCR (qPCR), luciferase reporter assay and chromatin immunoprecipitation (ChIP)-qPCR. We conducted functional assays in vitro and in a xenograft mouse model to evaluate the function of ATF3 in thyroid cancer. Integrated analysis based on RNA sequencing, ChIP-seq and CUT&Tag assays were performed to explore the mechanisms underlying the function of ATF3.ATF3 was significantly downregulated in PTC and patients with low ATF3 expression had reduced progression-free survival (adjusted hazard ratio = 0.50, 95% CI: 0.26-0.98, P = 0.043). DNA hypermethylation in ATF3 promoter disrupted the binding of SP1 and MYC-MAX, leading to inactivation of the gene. ATF3 functioned as a TSG by inhibiting the proliferation and mobility of thyroid cancer cells. And ATF3 regulated the expression of a number of genes by binding to the regulatory elements of them, particularly for genes in MAPK and PI3K/AKT pathways. Among these target genes, FLNC was positively regulated by ATF3 and associated with a more favorable thyroid cancer prognosis, while DUSP10, FN1, TNC, and CREB5 were negatively regulated by ATF3 and associated with a poorer prognosis.We observed that the promoter DNA hypermethylation decreased the expression of ATF3, which in turn promoted the progression of thyroid cancer, at least partially, by directly regulating prognosis-related genes in the MAPK and PI3K/AKT pathways.