Tea polyphenols induce S phase arrest and apoptosis in gallbladder cancer cells

Gallbladder cancer (GBC) is the most common malignancy in the biliary tract. Without effective treatment, its prognosis is notoriously poor. Tea polyphenols (TPs) have many pharmacological and health benefits, including antioxidant, anti-inflammatory, anti-tumor, anti-thrombotic, antibacterial, and vasodilatory properties. However, the anti-cancer effect of TPs in human gallbladder cancer has not yet been determined. Cell viability and colony formation assay were used to investigate the cell growth. Cell cycle and apoptosis were evaluated by flow cytometry analysis. Western blot assay was used to detect the expression of proteins related to cell cycle and apoptosis. Human tumor xenografts were used to examine the effect of TPs on gallbladder cancer cells in vivo. TPs significantly inhibited cell growth of gallbladder cancer cell lines in a dose- and time-dependent manner. Cell cycle progression in GBC cells was blocked at the S phase by TPs. TPs also induced mitochondrial-related apoptosis in GBC cells by upregulating Bax, cleaved caspase-3, and cleaved PARP expressions and downregulating Bcl-2, cyclin A, and Cdk2 expressions. The effects of TPs on GBC were further proven in vivo in a mouse xenograft model. Our study is the first to report that TPs inhibit GBC cell growth and these compounds may have potential as novel therapeutic agents for treating gallbladder cancer.胆囊癌（Gallbladder cancer, GBC）是胆道系统最常见的恶性肿瘤，若未接受有效治疗，其预后极差，已为学界公认。茶多酚（Tea polyphenols, TPs）具备多种药理与健康益处，涵盖抗氧化、抗炎、抗肿瘤、抗血栓、抗菌及血管舒张等活性。然而，茶多酚在人类胆囊癌中的抗癌效应尚未明确。本研究采用细胞活力检测与集落形成实验探究胆囊癌细胞的生长情况，通过流式细胞术分析评估细胞周期与细胞凋亡水平，运用蛋白质印迹（Western blot）实验检测与细胞周期及凋亡相关的蛋白表达，并构建人源肿瘤异种移植模型，在体内考察茶多酚对胆囊癌细胞的作用效果。实验结果表明，茶多酚可呈剂量与时间依赖性显著抑制胆囊癌细胞系的细胞生长，将胆囊癌细胞的细胞周期阻滞于S期。此外，茶多酚可通过上调Bax、切割型半胱天冬酶-3（cleaved caspase-3）及切割型多聚ADP核糖聚合酶（cleaved PARP）的表达，下调B细胞淋巴瘤-2（Bcl-2）、细胞周期蛋白A（cyclin A）与细胞周期蛋白依赖性激酶2（Cdk2）的表达，诱导胆囊癌细胞发生线粒体途径相关凋亡。上述效应在小鼠异种移植模型中得到了进一步验证。本研究首次证实茶多酚可抑制胆囊癌细胞生长，这类化合物有望成为治疗胆囊癌的新型治疗药物。