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 Thr⁴¹/Ser⁴⁵, 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 Thr⁴¹/Ser⁴⁵, 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.

中文翻译：

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FLI-1在调节CRC中通过Klotho信号传导介导肿瘤抑制功能。

大肠癌（CRC）是一种具有高发病率和高死亡率的侵袭性恶性肿瘤。尽管已经开发出靶向治疗方法，但远处转移的CRC患者的5年生存率仍然很低。因此，新靶标的鉴定对于改善CRC治疗仍然具有重要意义。Klotho是一种肿瘤抑制因子，在CRC中其表达异常。在这项研究中，在CRC细胞系中研究了 FLI-1基因在调节Klotho基因表达和Klotho相关信号中的作用，以及FLI-1对菌落形成，侵袭和凋亡的影响。使用商用甲基化试剂盒分析了FLI-1基因的甲基化。结果表明FLI-1与正常结肠粘膜上皮细胞系相比，六种CRC细胞系中的信使RNA和蛋白质表达下调，这与DNA甲基化水平呈负相关。沉默FLI-1基因表达下降Klotho蛋白质的表达和磷酸化β在苏氨酸蛋白连环蛋白⁴¹ /丝氨酸⁴⁵，但在HT29细胞中增加的Wnt3a和β连环蛋白的蛋白表达和IGF-1R磷酸化。与沉默FLI-1相反，过表达FLI-1在Thr ⁴¹ / Ser ^45时显着增加Klotho蛋白表达和β-catenin蛋白磷酸化，但降低Wnt3a和βCaco-2细胞中catenin蛋白表达和IGF-1R磷酸化。FLI-1基因表达的沉默显着增加了集落形成和侵袭，但减少了HT29细胞的凋亡。相反，过表达 FLI-1基因可显着减少集落形成和侵袭，但可增加Caco-2细胞的凋亡。这些发现表明，FLI-1在CRC细胞中起着抑癌作用，并积极调节Klotho信号传导。甲基化过高可能是CRC细胞中FLI-1基因表达缺失的原因之一。