BK21 Plus, Department of Cogno‑Mechatronics Engineering, Pusan National University, Busan 46241, Republic of Korea.
Department of Bio and Fermentation Convergence Technology, Kookmin University, Seoul 02707, Republic of Korea.
Int J Oncol. 2019 Apr;54(4):1295-1305. doi: 10.3892/ijo.2019.4724. Epub 2019 Feb 22.
The mechanisms through which cancer‑upregulated gene 2 (CUG2), a novel oncogene, affects Wnt/β‑catenin signaling, essential for tumorigenesis, are unclear. In this study, we aimed to elucidate some of these mechanisms in A549 lung cancer cells. Under the overexpression of CUG2, the protein levels and activity of β‑catenin were evaluated by western blot analysis and luciferase assay. To examine a biological consequence of β‑catenin under CUG2 overexpression, cell migration, invasion and sphere formation assay were performed. The upregulation of β‑catenin induced by CUG2 overexpression was also accessed by xenotransplantation in mice. We first found that CUG2 overexpression increased β‑catenin expression and activity. The suppression of β‑catenin decreased cancer stem cell (CSC)‑like phenotypes, indicating that β‑catenin is involved in CUG2‑mediated CSC‑like phenotypes. Notably, CUG2 overexpression increased the phosphorylation of β‑catenin at Ser33/Ser37, which is known to recruit E3 ligase for β‑catenin degradation. Moreover, CUG2 interacted with and enhanced the expression and kinase activity of never in mitosis gene A‑related kinase 2 (NEK2). Recombinant NEK2 phosphorylated β‑catenin at Ser33/Ser37, while NEK2 knockdown decreased the phosphorylation of β‑catenin, suggesting that NEK2 is involved in the phosphorylation of β‑catenin at Ser33/Ser37. Treatment with CGK062, a small chemical molecule, which promotes the phosphorylation of β‑catenin at Ser33/Ser37 through protein kinase C (PKC)α to induce its degradation, reduced β‑catenin levels and inhibited the CUG2‑induced features of malignant tumors, including increased cell migration, invasion and sphere formation. Furthermore, CGK062 treatment suppressed CUG2‑mediated tumor formation in nude mice. Taken together, the findings of this study suggest that CUG2 enhances the phosphorylation of β‑catenin at Ser33/Ser37 by activating NEK2, thus stabilizing β‑catenin. CGK062 may thus have potential for use as a therapeutic drug against CUG2‑overexpressing lung cancer cells.
癌症上调基因 2 (CUG2) 是一种新型癌基因，其影响肿瘤发生所必需的 Wnt/β-连环蛋白信号转导的机制尚不清楚。在这项研究中，我们旨在阐明 A549 肺癌细胞中其中的一些机制。通过 Western blot 分析和荧光素酶测定评估 CUG2 过表达时 β-连环蛋白的蛋白水平和活性。为了研究 CUG2 过表达下 β-连环蛋白的生物学后果，进行了细胞迁移、侵袭和球体形成测定。通过在小鼠中进行异种移植也检测了 CUG2 过表达诱导的 β-连环蛋白上调。我们首先发现 CUG2 过表达增加了 β-连环蛋白的表达和活性。β-连环蛋白的抑制降低了癌症干细胞 (CSC) 样表型，表明 β-连环蛋白参与了 CUG2 介导的 CSC 样表型。值得注意的是，CUG2 过表达增加了 β-连环蛋白 Ser33/Ser37 的磷酸化，这已知会募集 E3 连接酶以降解 β-连环蛋白。此外，CUG2 与并增强了有丝分裂基因 A 相关激酶 2 (NEK2) 的表达和激酶活性。重组 NEK2 使 β-连环蛋白 Ser33/Ser37 磷酸化，而 NEK2 敲低降低了 β-连环蛋白的磷酸化，表明 NEK2 参与了 β-连环蛋白 Ser33/Ser37 的磷酸化。通过蛋白激酶 C (PKC)α 促进 β-连环蛋白 Ser33/Ser37 磷酸化从而诱导其降解的小分子化合物 CGK062 的处理降低了 β-连环蛋白水平并抑制了 CUG2 诱导的恶性肿瘤特征，包括增加的细胞迁移、侵袭和球体形成。此外，CGK062 处理抑制了裸鼠中 CUG2 介导的肿瘤形成。总之，这项研究的结果表明，CUG2 通过激活 NEK2 增强了 β-连环蛋白 Ser33/Ser37 的磷酸化，从而稳定了 β-连环蛋白。CGK062 因此可能具有作为针对 CUG2 过表达肺癌细胞的治疗药物的潜力。
