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 Ca²⁺ 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.

肝细胞癌是最普遍的恶性疾病之一，并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进展。瑞格钙蛋白在与转录调控有关的钙信号传导中起抑制作用。Regucalcin基因表达在肝癌患者的肿瘤组织中被下调，提示其参与肝癌发生的抑制作用。我们研究了L型Ca ²⁺的激动剂Bay K 8644通道，促进人类肝癌的生长，如果使用HepG2细胞模型通过过表达的调钙素抑制了Bay K 8644的作用。通过与Bay K 8644（0.1-10 nM）培养，促进了HepG2细胞的集落形成和生长。这种作用被与细胞增殖相关的信号传导过程抑制剂（包括PD98059和渥曼青霉素）抑制。较高浓度（25和100 nM）的Bay K 8644刺激HepG2细胞死亡。钙通道拮抗剂维拉帕米消除了Bay K 8644对细胞生长和死亡的影响。从机理上讲，用Bay K 8644培养可提高丝裂原激活的蛋白激酶（MAPK）和磷酸化MAPK的水平。值得注意的是，过表达的regucalcin抑制了Bay K 8644促进的HepG2细胞生长和死亡。此外，过表达的瑞古钙蛋白阻止了毒胡萝卜素诱导的生长并增加了死亡，毒胡萝卜素诱导了细胞内储存钙的释放。因此，更高的瑞古钙素表达抑制了与肝癌细胞的生长相关的钙信号传导，从而通过递送瑞古钙素基因为肝细胞癌的治疗提供了新的策略。