The metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), inhibits pro-oncogenic signaling in pancreatic cancer (PC). This investigation dissected a novel mechanism induced by NDRG1 on WNT/β-catenin signaling in multiple PC cell types. NDRG1 overexpression decreased β-catenin and downregulated glycogen synthase kinase-3β (GSK-3β) protein levels and its activation. However, β-catenin phosphorylation at Ser33, Ser37, and Thr41 are classically induced by GSK-3β was significantly increased after NDRG1 overexpression, suggesting a GSK-3β-independent mechanism. Intriguingly, NDRG1 overexpression upregulated protein kinase Cα (PKCα), with silencing preventing β-catenin phosphorylation at Ser33, Ser37, and Thr41, and decreasing β-catenin expression. Further, NDRG1 and PKCα were demonstrated to associate, with PKCα stabilization occurring after NDRG1 overexpression. PKCα half-life increased from 1.5 ± 0.8 h (3) in control cells to 11.0 ± 2.5 h (3) after NDRG1 overexpression. Thus, NDRG1 overexpression leads to the association of NDRG1 with PKCα and PKCα stabilization, resulting in β-catenin phosphorylation at Ser33, Ser37, and Thr41. The association between PKCα, NDRG1, and β-catenin was identified, with the formation of a potential metabolon that promotes the latter β-catenin phosphorylation. This anti-oncogenic activity of NDRG1 was multi-modal, with the above mechanism accompanied by the downregulation of the nucleo-cytoplasmic shuttling protein, p21-activated kinase 4 (PAK4), which is involved in β-catenin nuclear translocation, inhibition of AKT phosphorylation (Ser473), and decreased β-catenin phosphorylation at Ser552 that suppresses its transcriptional activity. These mechanisms of NDRG1 activity are important to dissect to understand the marked anti-cancer efficacy of NDRG1-inducing thiosemicarbazones that upregulate PKCα and inhibit WNT signaling.

中文翻译：

---

转移抑制因子 NDRG1 的多模式机制：通过稳定蛋白激酶 Cα 抑制 WNT/β-连环蛋白信号传导


转移抑制因子 N-myc 下游调节基因 1 (NDRG1) 可抑制胰腺癌 (PC) 中的促癌信号传导。这项研究剖析了 NDRG1 在多种 PC 细胞类型中诱导 WNT/β-连环蛋白信号传导的新机制。 NDRG1 过表达会降低 β-连环蛋白并下调糖原合酶激酶-3β (GSK-3β) 蛋白水平及其激活。然而，GSK-3β 经典诱导的 Ser33、Ser37 和 Thr41 处的 β-连环蛋白磷酸化在 NDRG1 过表达后显着增加，表明 GSK-3β 不依赖的机制。有趣的是，NDRG1 过表达上调蛋白激酶 Cα (PKCα)，沉默可防止 β-连环蛋白 Ser33、Ser37 和 Thr41 磷酸化，并降低 β-连环蛋白表达。此外，NDRG1 和 PKCα 被证明具有相关性，且 NDRG1 过表达后 PKCα 稳定化。 NDRG1 过表达后，PKCα 半衰期从对照细胞中的 1.5 ± 0.8 h (3) 增加到 11.0 ± 2.5 h (3)。因此，NDRG1 过表达导致 NDRG1 与 PKCα 相关并稳定 PKCα，从而导致 Ser33、Ser37 和 Thr41 处的 β-连环蛋白磷酸化。鉴定了 PKCα、NDRG1 和 β-连环蛋白之间的关联，并形成了促进后者 β-连环蛋白磷酸化的潜在代谢物。 NDRG1 的这种抗癌活性是多模式的，上述机制伴随着核质穿梭蛋白 p21 激活激酶 4 (PAK4) 的下调，该蛋白参与 β-catenin 核转位，抑制 AKT磷酸化 (Ser473)，并减少 Ser552 处的 β-连环蛋白磷酸化，从而抑制其转录活性。 NDRG1 活性的这些机制对于剖析以了解 NDRG1 诱导的缩氨基硫脲上调 PKCα 并抑制 WNT 信号传导的显着抗癌功效非常重要。