背景 胰腺导管腺癌（PDAC）是一种高度致命、预后极差的消化道恶性肿瘤，晚期患者的中位生存期不足6个月，且治疗方案极其有限。DEAD-box RNA解旋酶3X （DEAD-box helicase 3X-linked，DDX3X）是一种多功能蛋白，与RNA代谢、病毒感染、细胞凋亡、炎症和癌症密切相关。雄性DDX3X敲除小鼠胚胎致死，提示DDX3X在生长发育中发挥着十分重要的作用。DDX3X既往被发现在肝癌、肺癌、结直肠癌等多种恶性肿瘤组织中高表达，并与肿瘤的发生、转移相关，而下调DDX3X表达能显著抑制肿瘤细胞的增殖和迁移。然而，DDX3X在胰腺导管腺癌进展中的具体作用尚不十分清楚。 目的 明确DDX3X在胰腺导管腺癌患者肿瘤组织以及胰腺癌细胞系中的表达水平，分析其与临床预后的相关性。进一步探讨DDX3X在胰腺导管腺癌进展中的具体作用及相关分子机制。 方法 通过生物信息学方法分析DDX3X在胰腺癌中的表达情况及其对临床预后的影响。免疫组织化学染色法检测DDX3X在PDAC患者肿瘤组织和癌旁正常组织中的表达。通过WB和RT-qPCR检测DDX3X在人源胰腺癌细胞系中的表达水平。通过CCK-8法、平板克隆法、Transwell侵袭法和划痕试验评价DDX3X在体外对胰腺癌细胞恶性行为的影响。通过裸鼠皮下成瘤模型和胰腺原位成瘤模型评价DDX3X在体内对肿瘤生长的影响。通过质谱、分子对接、免疫共沉淀（CO-IP）和细胞免疫荧光共定位等，寻找DDX3X的关键调控靶点并验证。多标记荧光法免疫组化染色（MIF）验证DDX3X，SIRT7和PD-L1的相关性。 结果 首先，DDX3X在胰腺导管腺癌中显著高表达，并且DDX3X高表达与胰腺癌的预后不良呈正相关。相较癌旁正常组织，DDX3X在PDAC患者肿瘤组织中明显升高。与人正常胰腺导管上皮细胞（HPDE）相比，九株胰腺癌细胞系中DDX3X蛋白和mRNA水平均明显较高。其次，在胰腺癌细胞中敲低DDX3X能够显著抑制胰腺癌细胞的增殖和侵袭、迁移能力，而过表达DDX3X则促进胰腺癌细胞的增殖和侵袭、迁移；在裸鼠皮下成瘤和胰腺原位成瘤模型中，过表达DDX3X均可促进肿瘤生长；相反，敲降DDX3X可以有效抑制肿瘤的生长。接着，质谱、分子对接、CO-IP以及细胞免疫荧光共定位结果均表明，SIRT7是DDX3X的关键调控靶点。体外实验显示，敲低DDX3X能引起胰腺癌细胞中SIRT7的蛋白表达水平下调，且SIRT7的mRNA水平也随着DDX3X变化而同向变化。然后，裸鼠皮下瘤和原位瘤模型均表明，SIRT7敲低后，DDX3X过表达对胰腺癌肿瘤的促生长作用被抑制。多标记荧光法免疫组化染色（MIF）显示DDX3X能影响肿瘤微环境中的PD-L1水平，进一步体外实验也证实，DDX3X过表达能显著升高CD274（编码PD-L1蛋白）的mRNA 水平。DDX3X与PD-L1在胰腺癌发展过程中可能存在协同作用，且两者高表达与胰腺癌预后不良存在显著正相关性。 结论 DDX3X通过与SIRT7相互作用促进胰腺导管腺癌的进展。此外，DDX3X能够调控PD-L1的表达，DDX3X可能成为新的胰腺癌治疗靶点。

Background Pancreatic ductal adenocarcinoma (PDAC) is recognized as the most aggressive and fatal malignancy, primarily due to late detection and insensitivity to chemotherapy and ionizing radiation. In essence, a thorough comprehension of the mechanisms that trigger PDAC and facilitate its progression could pave the way for prompt diagnosis and innovative, targeted treatment. The X-linked DEAD-box helicase 3 (DDX3X) protein is ubiquitously expressed in organisms. This ATP-dependent RNA helicase takes part in almost all steps of RNA metabolism. Prior studies have indicated that the absence of DDX3X in male mice results in premature lethality in the stage following implantation, highlighting the physiological significance of this protein in regulating development. Furthermore, an increasing body of evidence has suggested that dysregulation of DDX3X is commonly observed across different types of cancer. A previous study reported that PDAC patients who exhibit elevated levels of DDX3X have a poor prognosis and low overall survival rate. However, the underlying molecular mechanism remains unclear. Objective The present investigation sought to examine the potential molecular mechanisms of DDX3X in the progression of PDAC. Methods Multiple bioinformatics analyses were used to evaluate DDX3X expression and potential role in PDAC. Intro and vivo studies were performed to assess the effects of DDX3X on PDAC cells growth. Furthermore, western blotting, quantitative PCR, immunohistochemistry, mass spectrometry, molecular docking experiments, co-immunoprecipitation, immunofluorescence and multiplexed immunohistochemical staining was conducted to identify its specific regulatory mechanism in PDAC. Results The results verified that DDX3X expression is notably upregulated in the tumor tissue vs. normal tissue of PDAC patients. Elevated DDX3X expression is correlated with unfavorable outcomes in PDAC. DDX3X knockdown markedly suppressed the proliferation, invasion and migration of PDAC cells in vitro and inhibited tumor growth in vivo. Conversely, overexpression of DDX3X induced the opposite effect. Further studies supported that the DDX3X protein can associate with sirtuin 7 (SIRT7) to stimulate PDAC carcinogenesis and progression. Furthermore, SIRT7 inhibition significantly impeded DDX3X-mediated tumor growth both ex vivo and in vivo. The expression of DDX3X was positively correlated with CD274 (encoding PD-L1) in TCGA-PAAD cohort. What’s more, there was a positive correlation between the level of PD-L1 expression and that of the DDX3X protein in PDAC specimens. Additionally, upregulation of CD274 mRNA was observed in PANC-1 cells with DDX3X overexpression. And DDX3XhighCD274high patients could have worest outcomes. PD-L1 protein is also correlated with DDX3X-SIRT7 in PDAC patients’ tumor cells. Thus, DDX3X is linked to PD-L1. Conclusion Collectively, our findings provide a novel perspective on the distinct function of DDX3X in PDAC. We have effectively elucidated the pivotal role of the DDX3X-SIRT7 axis in PDAC. Our research findings suggest that targeting the constituents of this axis holds potential as a therapeutic strategy in the treatment of PDAC. Moreover, high DDX3X expression was found to be correlated with high PD-L1 expression in PDAC patients. This finding could hold considerable significance in increasing the clinical response rate and effectiveness of PD-1/PD-L1 blockade.