Department of Internal Medicine, Saga Medical School, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan.
Health Administration Center, Saga Medical School, Saga University, 5-1-1 Nabeshima, Saga 849-8501, Japan.
Int J Mol Sci. 2019 Feb 26;20(5):1022. doi: 10.3390/ijms20051022.
Hypoxia-inducible factor 1 (HIF-1) plays important roles in cancer cell biology. HIF-1α is reportedly activated by several factors, including protein kinase C (PKC), in addition to hypoxia. We investigated the role of PKC isoforms and the effects of vitamin K2 (VK2) in the activation process of HIF-1α. Human hepatocellular carcinoma (HCC)-derived Huh7 cells were cultured under normoxic and hypoxic (1% O₂) conditions with or without the PKC stimulator TPA. The expression, transcriptional activity and nuclear translocation of HIF-1α were examined under treatment with PKC inhibitors, siRNAs against each PKC isoform and VK2. Hypoxia increased the expression and activity of HIF-1α. TPA increased the HIF-1α activity several times under both normoxic and hypoxic conditions. PKC-δ siRNA-mediated knockdown, PKC-δ inhibitor (rottlerin) and pan-PKC inhibitor (Ro-31-8425) suppressed the expression and transcriptional activity of HIF-1α. VK2 significantly inhibited the TPA-induced HIF-1α transcriptional activity and suppressed the expression and nuclear translocation of HIF-1α induced by TPA without altering the HIF-1α mRNA levels. These data indicate that PKC-δ enhances the HIF-1α transcriptional activity by increasing the nuclear translocation, and that VK2 might suppress the HIF-1α activation through the inhibition of PKC in HCC cells.
缺氧诱导因子 1（HIF-1）在癌细胞生物学中发挥着重要作用。除了缺氧之外，HIF-1α 还被报道受多种因素激活，包括蛋白激酶 C（PKC）。我们研究了 PKC 同工型的作用以及维生素 K2（VK2）在 HIF-1α 激活过程中的作用。在有或没有 PKC 刺激剂 TPA 的情况下，将人肝癌（HCC）来源的 Huh7 细胞在常氧和缺氧（1% O₂）条件下培养。在使用 PKC 抑制剂、针对每种 PKC 同工型的 siRNA 和 VK2 处理后，检测 HIF-1α 的表达、转录活性和核易位。缺氧增加了 HIF-1α 的表达和活性。TPA 在常氧和缺氧条件下均可使 HIF-1α 活性增加数倍。PKC-δ siRNA 介导的敲低、PKC-δ 抑制剂（rottlerin）和泛 PKC 抑制剂（Ro-31-8425）抑制了 HIF-1α 的表达和转录活性。VK2 显著抑制了 TPA 诱导的 HIF-1α 转录活性，并抑制了 TPA 诱导的 HIF-1α 的表达和核易位，而不改变 HIF-1α mRNA 水平。这些数据表明，PKC-δ 通过增加核易位来增强 HIF-1α 的转录活性，并且 VK2 可能通过抑制 HCC 细胞中的 PKC 来抑制 HIF-1α 的激活。
