Colorectal cancer (CRC) is the fourth most deadly malignancy throughout the world. Extensive studies have shown that Krüppel-like factors (KLFs) play essential roles in cancer development. However, the function of KLF13 in CRC is unclear. The Cancer Genome Atlas database was applied to analyze the expression of KLF13 in CRC and normal tissues. Lentivirus system was used to overexpress and to knock down KLF13. RT-qPCR and Western blot assays were performed to detect mRNA and protein expression. CCK-8, colony formation, cell cycle analysis and EdU staining were used to assess the in vitro function of KLF13 in CRC cells. Xenografter tumor growth was used to evaluate the in vivo effect of KLF13 in CRC. Cholesterol content was measured by indicated kit. Transcription activity was analyzed by luciferase activity measurement. ChIP-qPCR assay was performed to assess the interaction of KLF13 to HMGCS1 promoter. KLF13 was downregulated in CRC tissues based on the TCGA database and our RT-qPCR and Western blot results. Comparing with normal colorectal cells NCM460, the CRC cells HT-26, HCT116 and SW480 had reduced KLF13 expression. Functional experiments showed that KLF13 knockdown enhanced the proliferation and colony formation in HT-29 and HCT116 cells. Opposite results were observed in KLF13 overexpressed cells. Furthermore, KLF13 overexpression resulted in cell cycle arrest at G0/G1 phase, reduced EdU incorporation and suppressed tumor growth of HCT116 cells in nude mice. Mechanistically, KLF13 transcriptionally inhibited HMGCS1 and the cholesterol biosynthesis. Knockdown of HMGCS1 suppressed cholesterol biosynthesis and the proliferation of CRC cells with silenced KLF13. Furthermore, cholesterol biosynthesis inhibitor significantly retarded the colony growth in both cells. Our study reveals that KLF13 acts as a tumor suppressor in CRC through negatively regulating HMGCS1-mediated cholesterol biosynthesis.

中文翻译：

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KLF13 通过转录抑制 HMGCS1 介导的胆固醇生物合成来抑制结直肠癌细胞的增殖和生长。

结直肠癌 (CRC) 是全球第四大最致命的恶性肿瘤。大量研究表明，Krüppel 样因子 (KLFs) 在癌症发展中发挥着重要作用。然而，KLF13 在 CRC 中的功能尚不清楚。应用癌症基因组图谱数据库分析 KLF13 在 CRC 和正常组织中的表达。慢病毒系统用于过表达和敲低 KLF13。进行 RT-qPCR 和蛋白质印迹分析以检测 mRNA 和蛋白质表达。CCK-8、集落形成、细胞周期分析和 EdU 染色用于评估 KLF13 在 CRC 细胞中的体外功能。异种移植肿瘤生长用于评估 KLF13 在 CRC 中的体内作用。通过指定的试剂盒测量胆固醇含量。通过荧光素酶活性测量分析转录活性。进行 ChIP-qPCR 测定以评估 KLF13 与 HMGCS1 启动子的相互作用。基于 TCGA 数据库和我们的 RT-qPCR 和蛋白质印迹结果，KLF13 在 CRC 组织中被下调。与正常结直肠细胞NCM460相比，CRC细胞HT-26、HCT116和SW480的KLF13表达降低。功能实验表明，KLF13 敲低增强了 HT-29 和 HCT116 细胞的增殖和集落形成。在 KLF13 过表达的细胞中观察到相反的结果。此外，KLF13 过表达导致细胞周期停滞在 G0/G1 期，减少 EdU 掺入并抑制裸鼠中 HCT116 细胞的肿瘤生长。从机制上讲，KLF13 转录抑制 HMGCS1 和胆固醇生物合成。敲除 HMGCS1 抑制了胆固醇的生物合成和具有沉默 KLF13 的 CRC 细胞的增殖。此外，胆固醇生物合成抑制剂显着延缓了两种细胞中的集落生长。我们的研究表明，KLF13 通过负调控 HMGCS1 介导的胆固醇生物合成在 CRC 中发挥肿瘤抑制作用。