Department of Gastroenterology, Tangdu Hospital, Fourth Military Medical University, Xi'an, China; State Key Laboratory of Cancer Biology, National Clinical Research Center for Digestive Diseases and Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China.
Department of Gastroenterology, The Affiliated Children's Hospital of Xi'an Jiaotong University, Xi'an, China.
J Biol Chem. 2022 Nov;298(11):102545. doi: 10.1016/j.jbc.2022.102545. Epub 2022 Sep 29.
Aberrant activation of the Wnt/β-catenin signaling pathway is implicated in most malignant cancers, especially in the initiation and progression of colorectal cancer (CRC). DKK4 is a classical inhibitory molecule of the Wnt/β-catenin pathway, but its role in CRC is ambiguous, and the molecular mechanism remains unclear. Here, we determined DKK4 expression was significantly upregulated in 23 CRC cell lines and 229 CRC tissues when analyzed by quantitative PCR and immunohistochemistry, respectively. Our analysis of tissue samples indicated the survival time of CRC patients with high DKK4 expression was longer than that of patients with medium-low DKK4 expression. We examined the effects of DKK4 on cell proliferation and metastasis by cell counting kit-8 assays, transwell assays, and subcutaneous and metastatic mouse tumor models, and we discovered that DKK4 silencing promoted the metastasis of CRC cells both in vitro and in vivo. Our RNA-seq analysis revealed that AKT2, FZD6, and JUN, which play important roles in AKT and Wnt signaling, were significantly increased after DKK4 knockdown. DKK4 represses Wnt/β-catenin signaling by repressing FZD6 and AKT2/s552 β-catenin in CRC. Further experiments revealed recombinant Wnt3a and LiCl could induce DKK4 expression. Moreover, our bioinformatics analysis and luciferase reporter assays identified posttranscriptional regulators of DKK4 in CRC cells. In summary, DKK4 is elevated in CRC and inhibits cell metastasis by a novel negative feedback mechanism of the Wnt3a/DKK4/AKT/s552 β-catenin regulatory axis to restrict overactivation of Wnt activity in CRC. Therefore, DKK4 restoration may be applied as a potential CRC therapeutic strategy.
Wnt/β-catenin 信号通路的异常激活与大多数恶性肿瘤有关，尤其是在结直肠癌（CRC）的发生和进展中。DKK4 是 Wnt/β-catenin 通路的经典抑制分子，但它在 CRC 中的作用尚不清楚，其分子机制仍不清楚。在这里，我们通过定量 PCR 和免疫组织化学分别分析了 23 种 CRC 细胞系和 229 种 CRC 组织中 DKK4 的表达情况，结果显示 DKK4 的表达显著上调。我们对组织样本的分析表明，高 DKK4 表达的 CRC 患者的生存时间长于中低 DKK4 表达的患者。我们通过细胞计数试剂盒-8 检测、Transwell 检测以及皮下和转移性小鼠肿瘤模型检测了 DKK4 对细胞增殖和转移的影响，发现 DKK4 沉默促进了 CRC 细胞在体外和体内的转移。我们的 RNA-seq 分析显示，AKT2、FZD6 和 JUN 在 DKK4 敲低后显著增加，它们在 AKT 和 Wnt 信号中发挥重要作用。DKK4 通过抑制 FZD6 和 AKT/s552 β-catenin 抑制 CRC 中的 Wnt/β-catenin 信号。进一步的实验表明，重组 Wnt3a 和 LiCl 可以诱导 DKK4 的表达。此外，我们的生物信息学分析和荧光素酶报告基因检测鉴定了 CRC 细胞中 DKK4 的转录后调节因子。总之，DKK4 在 CRC 中上调，并通过 Wnt3a/DKK4/AKT/s552 β-catenin 调节轴的新的负反馈机制抑制细胞转移，以限制 Wnt 活性在 CRC 中的过度激活。因此，DKK4 的恢复可能作为一种潜在的 CRC 治疗策略。
