ATF3在砷致支气管上皮细胞损伤、恶性转化和EMT中的作用及机制

ATF3 is a transcription factor that contains a basic-region leucine zipper (bZIP) domain and is responsive to a variety of stress factors. The expression level of ATF3 is associated with initiation, progression, invasion and metastasis of various cancers, but the mechanism remains unclear. Our group has observed that arsenic upregulated ATF3 in human bronchial epithelial cells (BEAS-2B), and upregulation of ATF3 mediated the expression of CDC25A, GADD45α and Egr-1. This project will establish two in vitro models: high concentration arsenic-mediated cell injury and low dose arsenic-induced BEAS-2B transformation, and use techniques including anti-sense techniques and molecular biology techniques to reveal the effect of ATF3 on arsenic-induced BEAS-2B cell injury, transformation and epithelial-mesenchymal transition (EMT). The ultimate purpose is to understand the inhibitory role of ATF3 in arsenic-induced lung cancer and to provide supporting evidence to identify ATF3 as a target for prevention, treatment and prognosis of arsenic-induced lung cancer.

ATF3是含亮氨酸拉链结构的转录因子，可被多种应激因子激活。ATF3表达水平与多种肿瘤的发生发展和侵袭转移有关，但机制尚未阐明。本课题组预实验发现，砷可上调ATF3在人支气管上皮细胞（BEAS-2B）中的表达，且ATF3上调对CDC25A、GADD45α和Egr-1的表达有调控作用。本项目将建立高浓度砷引起BEAS-2B细胞损伤模型和低浓度砷诱导BEAS-2B细胞恶性转化模型，应用反义技术、分子生物学手段等，揭示ATF3对砷致支气管上皮细胞损伤、恶性转化和上皮间质转化（EMT）的作用，探究ATF3对砷致肺癌的抑制作用及机制，为发展ATF3为砷致肺癌预防、治疗及预后的靶点提供依据。

ATF3是含亮氨酸拉链结构（bZIP）的转录因子，在正常细胞中呈低浓度稳态表达，被损伤性应激信号诱导后表达会迅速升高。ATF3依靠ZIP结构形成同源或异源二聚体，与DNA上的CRE结合调控基因转录。另外，ATF3也可与蛋白发生相互作用，从而影响蛋白活性及稳定性。ATF3在不同生理和病理情况下发挥着不同作用，但是其在支气管上皮细胞损伤及肺癌中的作用尚未明确。本课题研究发现高剂量砷可迅速增加ATF3表达，而后ATF3可通过与启动子结合的方式上调DR5表达，下调Bcl-xL表达，从而促进砷引起的支气管上皮细胞细胞凋亡。而在长期低剂量砷暴露情况下，ATF3的表达也会上调。通过建立ATF3稳定敲除的细胞株，我们发现ATF3的缺失会使支气管上皮细胞更易发生砷致恶性转化，且发生恶性转化的细胞恶性程度更高，例如抗凋亡能力增强、侵袭能力增强、增殖能力增强等。之后，我们比较了不同信号通路的激活情况后，发现ATF3敲除的恶性转化细胞IL-6-AKT/STAT3信号通路活性较强，说明ATF3抑制恶性转化的作用是通过下调IL-6发挥的。综上所述，ATF3在砷致细胞损伤中起到了促凋亡作用，而在砷致肺癌癌变过程中扮演了抑癌角色。