Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers with an extremely poor prognosis. Gemcitabine (Gem) is still the mainstay drug for the treatment of PDAC. However, rapid inactivation by cytidine deaminase (CDA) present in pancreatic cancer cells severely limits anticancer efficacy of Gem. In this study, we investigated the effect of a CDA inhibitor - Zebularine (Zeb) on anticancer activity of Gem in pancreatic cancer cell lines MiaPaCa-2, BxPC-3, and Panc-1. Zeb treatment synergistically increased Gem-induced cytotoxicity in all three pancreatic cancer cell lines. The strongest synergistic activity was found at 1:10 M ratio of Gem/Zeb (combination index 0.04–0.4). Additionally, Gem + Zeb treated cells showed marked decreased in the expressions of anti-apoptotic protein including Bcl-2 and survivin while significantly increased the cleaved caspase-3, and loss of mitochondrial membrane potential was observed. Multicellular 3D spheroids of MiaPaCa-2 cells treated with combination showed significant reduction (25–60%) in spheroid size, weight compared to single drug and control group. Live/dead cell imaging showed that Gem + Zeb treated spheroids exhibited a highly distorted surface with significantly higher number of dead cells (red). The results of the present study confirm that this synergistic combination is worthy of future investigations as a potential approach for the treatment of PDAC.

胰腺导管腺癌（PDAC）是最致命的癌症之一，预后极差。吉西他滨（Gem）仍然是治疗 PDAC 的主要药物。然而，胰腺癌细胞中胞苷脱氨酶 (CDA) 的快速失活严重限制了 Gem 的抗癌功效。在这项研究中，我们研究了 CDA 抑制剂 Zebularine (Zeb) 对 Gem 在胰腺癌细胞系 MiaPaCa-2、BxPC-3 和 Panc-1 中的抗癌活性的影响。 Zeb 治疗可协同增加所有三种胰腺癌细胞系中 Gem 诱导的细胞毒性。 Gem/Zeb 的比例为 1:10 M 时发现最强的协同活性（组合指数 0.04-0.4）。此外，Gem + Zeb 处理的细胞显示，包括 Bcl-2 和 survivin 在内的抗凋亡蛋白的表达显着下降，而 cleaved caspase-3 的表达显着增加，并且观察到线粒体膜电位丧失。与单一药物和对照组相比，联合治疗的 MiaPaCa-2 细胞的多细胞 3D 球体的球体大小、重量显着减少 (25-60%)。活/死细胞成像显示，Gem + Zeb 处理的球体表现出高度扭曲的表面，死细胞数量显着增加（红色）。本研究的结果证实，这种协同组合作为治疗 PDAC 的潜在方法值得未来研究。