Death domain-associated protein (DAXX) is a complex biological multifunctional protein and is involved in the tumorigenesis and progression of multiple cancers. The accumulation of DAXX in the nucleus is a common phenomenon in tumor cells. However, altering the subcellular localizations of DAXX results in different biological functions, and we also found that its nuclear/cytoplasmic ratio (NCR) was associated with poor prognosis in gastric cancer (GC). In this study, we investigated the effect of cytoplasmic and nuclear DAXX (cDAXX and nDAXX) in GC and the underlying mechanisms. Immunohistochemical detection performed in 323 GC tissues reveled that cDAXX was associated with a better survival, while high nDAXX expression suggested a poorer prognosis outcome. Upregulation of DAXX in the cytoplasm inhibited cell proliferation and promoted apoptosis, whereas downregulation of DAXX in the nucleus displayed opposite effects. Moreover, Transwell assays revealed that DAXX enhanced GC cell migration and invasion. Analysis from the Gene Expression Profile Interactive Analysis (GEPIA) database showed that the expression of DAXX was significantly associated with SUMO-2/3 in GC tissues. Co-immunoprecipitation combined with immunofluorescence analysis indicated that DAXX interacted directly with SUMO-2/3. Subsequently, down-regulating the expression of SUMO-2/3 resulted in altered subcellular localization of DAXX. Bioinformatics analysis showed that RanBP2 may act as SUMO E3 ligase to promote nuclear-plasma transport via combining with RanGAP1. Taken together, our results indicated that DAXX plays opposing roles in GC and suggest a new model whereby cDAXX, nDAXX, and SUMO-2/3 form a molecular network that regulates the subcellular localization of DAXX and thereby modulates its opposing biological effects. Thus, our findings provide a foundation for future studies of DAXX as a novel therapeutic target for patients with GC.

死亡域相关蛋白（DAXX）是一种复杂的生物学多功能蛋白，参与多种癌症的发生和发展。DAXX在细胞核中的积累是肿瘤细胞中的常见现象。但是，改变DAXX的亚细胞定位会导致不同的生物学功能，我们还发现其核/细胞质比（NCR）与胃癌（GC）的预后不良有关。在这项研究中，我们调查了细胞质和核DAXX（cDAXX和nDAXX）在GC中的作用及其潜在机制。在323个GC组织中进行的免疫组织化学检测显示，cDAXX与更好的生存率相关，而nDAXX高表达提示预后较差。细胞质中DAXX的上调抑制细胞增殖并促进细胞凋亡，而DAXX在细胞核中的下调显示相反的作用。此外，Transwell分析表明DAXX增强了GC细胞的迁移和侵袭。基因表达谱交互式分析（GEPIA）数据库的分析表明，DAXX的表达与GC组织中的SUMO-2 / 3显着相关。免疫共沉淀结合免疫荧光分析表明DAXX与SUMO-2 / 3直接相互作用。随后，下调SUMO-2 / 3的表达导致DAXX的亚细胞定位改变。生物信息学分析表明，RanBP2可以作为SUMO E3连接酶，通过与RanGAP1结合来促进核质运输。综上，我们的结果表明DAXX在GC中起相反的作用，并提出了一种新的模型，其中cDAXX，nDAXX SUMO-2 / 3和SUMO-2 / 3形成一个分子网络，该分子网络调节DAXX的亚细胞定位，从而调节其相反的生物学作用。因此，我们的发现为DAXX作为GC患者的新型治疗靶标的未来研究奠定了基础。