Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
Division of Hematology and Oncology, Department of Medicine, Cardinal Tien Hospital, New Taipei City, Taiwan.
Liver Int. 2018 Dec;38(12):2248-2259. doi: 10.1111/liv.13887. Epub 2018 Jun 12.
BACKGROUND & AIMS: Few molecules are currently verified to be actionable drug targets in cholangiocarcinoma (CCA). Serine/threonine protein phosphatase 5 (PP5) dysregulation is related to several malignancies. However, the role of PP5 in CCA is poorly defined.
Colony and tumorsphere formation assays were conducted to establish the role of PP5 in CCA tumorigenesis. Cantharidin (CTD) and norcantharidin (NCTD), both potent PP5 inhibitors, were used in in vitro and in vivo experiments to validate the potential therapeutic role of PP5.
Increased cell growth, colony formation and tumorsphere formation were observed in PP5-overexpressing CCA cells, whereas PP5 knockdown by shRNA decreased cell growth and colony formation. Tumours from HuCCT1 xenograft-bearing mice treated with PP5-shRNA showed decreased growth and increased AMP-activated protein kinase (AMPK) phosphorylation. Furthermore, CTD treatment decreased cell viability, reduced PP5 activity and enhanced AMPK phosphorylation in CCA cell lines. Overexpressing PP5 or enhancing PP5 activity suppressed AMPK phosphorylation and decreased CTD-induced cell death. Suppressing p-AMPK with siRNA or inhibitors also decreased CTD-induced cell death, suggesting a pivotal role for PP5-AMPK cascades in CCA. Immunoprecipitation revealed that PP5 interacted with AMPK. Importantly, treatment of HuCCT1 xenograft-bearing mice with NCTD, a CTD analogue with a lower systemic toxicity in vivo, suppressed PP5 activity, increased p-AMPK and reduced tumour volume.
Protein phosphatase 5 negatively regulates AMPK phosphorylation and contributes to CCA aggressiveness; thus, PP5 may be a potential therapeutic target in CCA.
目前仅有少数分子被证实可作为胆管癌（CCA）的治疗靶点。丝氨酸/苏氨酸蛋白磷酸酶 5（PP5）失调与多种恶性肿瘤有关。然而，PP5 在 CCA 中的作用尚未明确。
通过集落和肿瘤球形成实验来确定 PP5 在 CCA 肿瘤发生中的作用。我们使用有效的 PP5 抑制剂斑蝥素（CTD）和去甲斑蝥素（NCTD）进行体内外实验，以验证 PP5 的潜在治疗作用。
在过表达 PP5 的 CCA 细胞中，观察到细胞生长、集落形成和肿瘤球形成增加，而 shRNA 下调 PP5 则降低了细胞生长和集落形成。用 PP5-shRNA 处理荷 HuCCT1 移植瘤的小鼠的肿瘤显示出生长减少和 AMP 激活的蛋白激酶（AMPK）磷酸化增加。此外，CTD 处理降低了 CCA 细胞系的细胞活力，降低了 PP5 活性并增强了 AMPK 磷酸化。过表达 PP5 或增强 PP5 活性抑制了 AMPK 磷酸化并减少了 CTD 诱导的细胞死亡。用 siRNA 或抑制剂抑制 p-AMPK 也减少了 CTD 诱导的细胞死亡，表明 PP5-AMPK 级联在 CCA 中起关键作用。免疫沉淀显示 PP5 与 AMPK 相互作用。重要的是，用 NCTD（一种体内系统毒性较低的 CTD 类似物）治疗荷 HuCCT1 移植瘤的小鼠，抑制了 PP5 活性，增加了 p-AMPK，并减少了肿瘤体积。
蛋白磷酸酶 5 负调控 AMPK 磷酸化并促进 CCA 的侵袭性；因此，PP5 可能是 CCA 的潜在治疗靶点。
