Department of Laboratory Medicine, the First People's Hospital of Yancheng City/Affiliated Hospital 4 of Nantong University, Yancheng, Jiangsu Province, China.
Department of Laboratory Medicine, Affiliated Hospital of Nantong University, Nantong, Jiangsu Province, China.
Clin Epigenetics. 2021 Apr 23;13(1):89. doi: 10.1186/s13148-021-01071-z.
Aberrant DNA methylation has been firmly established as a factor contributing to the pathogenesis of colorectal cancer (CRC) via its capacity to silence tumour suppressor genes. However, the methylation status of multiple tumour suppressor genes and their roles in promoting CRC metastasis are not well characterised.
We explored the methylation and expression profiles of CPEB1 (the gene encoding cytoplasmic polyadenylation element-binding protein 1), a candidate CRC tumour suppressor gene, using The Cancer Genome Atlas (TCGA) database and validated these results in both CRC cell lines and cells from Han Chinese CRC patients (n = 104). The functional role of CPEB1 in CRC was examined in experiments performed in vitro and in vivo. A candidate transcription factor capable of regulating CPEB1 expression was predicted in silico and validated by luciferase reporter, DNA pull-down, and electrophoretic mobility shift assays.
Hypermethylation and decreased expression of CPEB1 in CRC tumour tissues were revealed by TCGA database. We also identified a significant inverse correlation (Pearson's R = - 0.43, P < 0.001) between promoter methylation and CPEB1 expression. We validated these results in CRC samples and two CRC cell lines. We also demonstrated that up-regulation of CPEB1 resulted in significantly decreased tumour growth, migration, invasion, and tumorigenicity and promoted tumour cell apoptosis both in vitro and in vivo. We identified the transcription factors CCAAT enhancer-binding protein beta (CEBPB) and transcription factor CP2 (TFCP2) as critical regulators of CPEB1 expression. Hypermethylation of the CPEB1 promoter resulted in a simultaneous increase in the capacity for TFCP2 binding and a decreased likelihood of CEBPB binding, both of which led to diminished expression of CPEB1.
Our results identified a novel tumour-suppressive role of CPEB1 in CRC and found that hypermethylation of the CPEB1 promoter may lead to diminished expression due to decreased chromatin accessibility and transcription factor binding. Collectively, these results suggest a potential role for CPEB1 in the diagnosis and treatment of CRC.
异常的 DNA 甲基化已被确定为导致结直肠癌（CRC）发病机制的一个因素，因为它能够使肿瘤抑制基因沉默。然而，多个肿瘤抑制基因的甲基化状态及其在促进 CRC 转移中的作用尚不清楚。
我们使用癌症基因组图谱（TCGA）数据库研究了 CPEB1（编码细胞质多聚腺苷酸化元件结合蛋白 1 的基因）的甲基化和表达谱，CPEB1 是候选 CRC 肿瘤抑制基因，并在 CRC 细胞系和来自中国汉族 CRC 患者的细胞中验证了这些结果（n=104）。在体外和体内实验中研究了 CPEB1 在 CRC 中的功能作用。通过荧光素酶报告基因、DNA 下拉和电泳迁移率变动分析预测了一种能够调节 CPEB1 表达的候选转录因子，并进行了验证。
TCGA 数据库揭示了 CRC 肿瘤组织中 CPEB1 的高甲基化和表达降低。我们还发现启动子甲基化与 CPEB1 表达之间存在显著的负相关（Pearson's R=-0.43，P<0.001）。我们在 CRC 样本和两个 CRC 细胞系中验证了这些结果。我们还证明，上调 CPEB1 可显著降低肿瘤生长、迁移、侵袭和致瘤性，并促进肿瘤细胞凋亡，无论是在体外还是体内。我们确定转录因子 CCAAT 增强子结合蛋白β（CEBPB）和转录因子 CP2（TFCP2）是 CPEB1 表达的关键调节因子。CPEB1 启动子的高甲基化导致 TFCP2 结合能力同时增加，CEBPB 结合的可能性降低，这两者都导致 CPEB1 的表达降低。
我们的结果确定了 CPEB1 在 CRC 中的新的肿瘤抑制作用，并发现 CPEB1 启动子的高甲基化可能导致由于染色质可及性和转录因子结合降低而导致的表达降低。总的来说，这些结果表明 CPEB1 在 CRC 的诊断和治疗中可能具有潜在作用。
