The CDX1-microRNA-215 axis regulates colorectal cancer stem cell differentiation
The CDX1-microRNA-215 axis regulates colorectal cancer stem cell differentiation
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DOI：
10.1073/pnas.1503370112
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发表时间：
2015-03-31
影响因子：
11.1
通讯作者：
Lal, Ashish
中科院分区：
文献类型：
--
作者：
Jones, Matthew F.;Hara, Toshifumi;Lal, Ashish
转录因子尾型同源框1（CDX 1）是正常结肠和结直肠癌（CRC）分化的关键调节因子。CDX 1激活肠上皮细胞基因的表达，但尚不清楚如何实现干细胞基因的伴随沉默。微小RNA（miRNAs）是基因抑制的重要介质，并与肿瘤抑制和癌变有关，但miRNAs在分化中的作用，特别是在CRC中，仍然知之甚少。在这里，我们通过使用高通量小RNA测序来分析两对CRC细胞系中的miRNA表达，将microRNA-215（miR-215）鉴定为CDX 1的直接转录靶点：CDX 1低水平的HCT 116和稳定CDX 1过表达的HCT 116，以及CDX 1高水平的LS 174 T和稳定CDX 1敲低的LS 174 T。在更大的细胞系组中通过RNA-seq鉴定的候选miRNA的验证显示miR-215与CDX 1表达最显著相关。定量ChIP-PCR和启动子荧光素酶测定证实CDX 1直接激活miR-215转录。与未分选的样品相比，miR-215表达在FACS富集的癌症干细胞中耗尽。miR-215在低分化细胞系中的过表达导致克隆形成性降低，而miR-215敲低增加克隆形成性并损害CDX 1高细胞系的分化。我们确定了miR-215的全基因组靶点，并发现miR-215介导了CDX 1下游细胞周期和干性基因的抑制。特别是，miR-215靶基因BMI 1已显示出促进干性和自我更新，并与CDX 1呈反比变化。我们的工作将miR-215定位为CDX 1表达和控制CRC分化的BMI 1抑制之间的联系。
The transcription factor caudal-type homeobox 1 (CDX1) is a key regulator of differentiation in the normal colon and in colorectal cancer (CRC). CDX1 activates the expression of enterocyte genes, but it is not clear how the concomitant silencing of stem cell genes is achieved. MicroRNAs (miRNAs) are important mediators of gene repression and have been implicated in tumor suppression and carcinogenesis, but the roles of miRNAs in differentiation, particularly in CRC, remain poorly understood. Here, we identified microRNA-215 (miR-215) as a direct transcriptional target of CDX1 by using high-throughput small RNA sequencing to profile miRNA expression in two pairs of CRC cell lines: CDX1-low HCT116 and HCT116 with stable CDX1 overexpression, and CDX1-high LS174T and LS174T with stable CDX1 knockdown. Validation of candidate miRNAs identified by RNA-seq in a larger cell-line panel revealed miR-215 to be most significantly correlated with CDX1 expression. Quantitative ChIP-PCR and promoter luciferase assays confirmed that CDX1 directly activates miR-215 transcription. miR-215 expression is depleted in FACS-enriched cancer stem cells compared with unsorted samples. Overexpression of miR-215 in poorly differentiated cell lines causes a decrease in clonogenicity, whereas miR-215 knockdown increases clonogenicity and impairs differentiation in CDX1-high cell lines. We identified the genome-wide targets of miR-215 and found that miR-215 mediates the repression of cell cycle and stemness genes downstream of CDX1. In particular, the miR-215 target gene BMI1 has been shown to promote stemness and self-renewal and to vary inversely with CDX1. Our work situates miR-215 as a link between CDX1 expression and BMI1 repression that governs differentiation in CRC.