Cancer Biology Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, 701 Ilalo Street, Honolulu, HI, 96813, USA.
Laboratory of Analytical Neurobiology, Faculty of Pharmacy, Meijo University, Yagotoyama 150, Tempaku, Nagoya, 468-8503, Japan.
Mol Cell Biochem. 2020 Sep;472(1-2):173-185. doi: 10.1007/s11010-020-03795-7. Epub 2020 Jun 26.
Hepatocellular carcinoma is one of the most prevalent malignant diseases and causes a third of cancer-related death. The consequences of altered calcium homeostasis in cancer cells may contribute to tumor progression. Regucalcin plays an inhibitory role in calcium signaling linked to transcription regulation. Regucalcin gene expression is downregulated in the tumor tissues of liver cancer patients, suggesting an involvement as a suppressor in hepatocarcinogenesis. We investigated whether Bay K 8644, an agonist of the L-type Ca channel, promotes the growth of human liver cancer and if the effect of Bay K 8644 is suppressed by overexpressed regucalcin using the HepG2 cell model. The colony formation and growth of HepG2 cells were promoted by culturing with Bay K 8644 (0.1-10 nM). This effect was suppressed by inhibitors of signaling processes linked to cell proliferation, including PD98059 and wortmannin. Death of HepG2 cells was stimulated by Bay K 8644 with higher concentrations (25 and 100 nM). The effects of Bay K 8644 on cell growth and death were abolished by verapamil, an antagonist of calcium channel. Mechanistically, culturing with Bay K 8644 increased levels of mitogen-activated protein kinase (MAPK) and phospho-MAPK. Notably, overexpressed regucalcin suppressed Bay K 8644-promoted growth and death of HepG2 cells. Furthermore, overexpressed regucalcin prevented growth and increased death induced by thapsigargin, which induces the release of intracellular stored calcium. Thus, higher regucalcin expression suppresses calcium signaling linked to the growth of liver cancer cells, providing a novel strategy in treatment of hepatocellular carcinoma with delivery of the regucalcin gene.
肝细胞癌是最常见的恶性疾病之一，导致三分之一的癌症相关死亡。癌细胞中钙稳态的改变可能导致肿瘤的进展。钙调节蛋白在与转录调节相关的钙信号中发挥抑制作用。钙调节蛋白基因在肝癌患者的肿瘤组织中表达下调，表明其在肝癌发生中作为抑制因子发挥作用。我们研究了 L 型钙通道激动剂 Bay K 8644 是否促进人肝癌的生长，以及过表达钙调节蛋白是否抑制 Bay K 8644 对 HepG2 细胞的作用。用 Bay K 8644（0.1-10 nM）培养可促进 HepG2 细胞集落的形成和生长。这种作用被与细胞增殖相关的信号通路抑制剂 PD98059 和wortmannin 抑制。较高浓度（25 和 100 nM）的 Bay K 8644 刺激 HepG2 细胞死亡。钙通道拮抗剂 verapamil 可消除 Bay K 8644 对细胞生长和死亡的影响。从机制上讲，用 Bay K 8644 培养可增加丝裂原活化蛋白激酶（MAPK）和磷酸化 MAPK 的水平。值得注意的是，过表达钙调节蛋白可抑制 Bay K 8644 促进 HepG2 细胞的生长和死亡。此外，过表达钙调节蛋白可防止由 thapsigargin 诱导的细胞生长和死亡增加，thapsigargin 可诱导细胞内储存的钙释放。因此，较高的钙调节蛋白表达抑制与肝癌细胞生长相关的钙信号，为通过基因传递治疗肝细胞癌提供了一种新策略。
