Department One of Anorectal Surgery, The Second Affiliated Hospital of Hunan University of Chinese Medicine, Changsha, 410005, Hunan, China.
Hunan Slack King Laboratory Animal Co., Ltd., Changsha, 410125, Hunan, China.
Cell Biol Int. 2020 Jul;44(7):1514-1522. doi: 10.1002/cbin.11347. Epub 2020 Apr 3.
Colorectal cancer (CRC) is an aggressive malignancy with a high incidence and mortality rate. Although a targeting therapy has been developed, the 5-year survival rate is still very low in CRC patients with distant metastasis. Thus, the identification of new targets is still significant for improving CRC treatment. Klotho is a tumor suppressor, and its expression is aberrant in CRC. In this study, the roles of the FLI-1 gene in regulating Klotho gene expression and Klotho-associated signaling, as well as the effects of FLI-1 on colony formation, invasion, and apoptosis were investigated in CRC cell lines. The methylation of the FLI-1 gene was analyzed using a commercial methylation kit. Results showed that FLI-1 messenger RNA and protein expression were downregulated in six CRC cell lines when compared with the normal colon mucosal epithelial cell line, which negatively correlated with the level of DNA methylation. Silencing of FLI-1 gene expression decreased Klotho protein expression and phosphorylation of β-catenin protein at Thr /Ser , but increased Wnt3a and β-catenin protein expression and IGF-1R phosphorylation in HT29 cells. In contrast to silencing FLI-1, overexpressing FLI-1 significantly increased Klotho protein expression and phosphorylation of β-catenin protein at Thr /Ser , but decreased Wnt3a and β-catenin protein expression and IGF-1R phosphorylation in Caco-2 cells. Silencing of FLI-1 gene expression significantly increased colony formation and invasion, but decreased apoptosis in HT29 cells. In contrast, overexpressing the FLI-1 gene significantly decreased colony formation and invasion, but increased apoptosis in Caco-2 cells. These findings suggest that FLI-1 functions as a tumor suppressor in CRC cells and positively regulates Klotho signaling. Hypermethylation may be one of the causes of the loss of FLI-1 gene expression in CRC cells.
结直肠癌（CRC）是一种侵袭性恶性肿瘤，发病率和死亡率都很高。尽管已经开发出了一种靶向治疗方法，但对于远处转移的 CRC 患者，其 5 年生存率仍然非常低。因此，寻找新的靶点对于改善 CRC 的治疗仍然具有重要意义。Klotho 是一种肿瘤抑制因子，其在 CRC 中的表达异常。在这项研究中，研究了 FLI-1 基因在调节 Klotho 基因表达和 Klotho 相关信号通路中的作用，以及 FLI-1 对 CRC 细胞系集落形成、侵袭和凋亡的影响。使用商业甲基化试剂盒分析了 FLI-1 基因的甲基化。结果表明，与正常结肠黏膜上皮细胞系相比，在六个 CRC 细胞系中，FLI-1 信使 RNA 和蛋白表达下调，与 DNA 甲基化水平呈负相关。沉默 FLI-1 基因表达降低了 HT29 细胞中 Klotho 蛋白表达和 β-catenin 蛋白 Thr/Ser 磷酸化，但增加了 Wnt3a 和 β-catenin 蛋白表达以及 IGF-1R 磷酸化。与沉默 FLI-1 相反，过表达 FLI-1 显著增加了 Caco-2 细胞中 Klotho 蛋白表达和 β-catenin 蛋白 Thr/Ser 磷酸化，但降低了 Wnt3a 和 β-catenin 蛋白表达以及 IGF-1R 磷酸化。沉默 FLI-1 基因表达显著增加了 HT29 细胞集落形成和侵袭，但降低了细胞凋亡。相反，过表达 FLI-1 显著降低了 Caco-2 细胞的集落形成和侵袭，但增加了细胞凋亡。这些发现表明，FLI-1 在 CRC 细胞中作为肿瘤抑制因子发挥作用，并正向调节 Klotho 信号通路。高甲基化可能是 CRC 细胞中 FLI-1 基因表达缺失的原因之一。
