Department of Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Department of Breast Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Mol Cancer Res. 2016 Apr;14(4):354-62. doi: 10.1158/1541-7786.MCR-15-0380. Epub 2016 Jan 8.
miRNAs have important roles in regulating cancer stem cell (CSC) properties and are considered to be potential therapeutic targets. However, few studies have focused on miRNAs which are specifically related to colon CSCs. Here, a PCR-based miRNA profiling analysis of normal colon stem cells (NCSC) and colon CSCs (EpCAM⁺/CD44⁺/CD66a⁻) identified miRNAs which regulate colon CSC properties. Interestingly, miRNA-137 (miR-137) expression was downregulated in the colon CSCs compared with NCSCs, while doublecortin-like kinase 1(DCLK1) mRNA was highly expressed in the colon CSCs but low in the NCSCs. In fact, DCLK1-positive cancer cells were widely distributed in clinically resected colon cancer specimens, while DCLK1-positve epithelial cells were rarely detected in normal colon tissues including the crypt bottoms. Luciferase assay and immunoblot analysis revealed that miR-137 regulated DCLK1 gene expression. Transduction of exogenous miR-137 suppressed the development of colon cancer organoids in vitro and the tumorigenicity of colon cancer cells in vivo without affecting the growth of normal intestinal organoids. Furthermore, the suppression of miR-137 enhanced the organoid development of normal colon cells. These data demonstrate that miR-137 has the capacity to suppress the tumorigenicity of colon CSCs and that maintained expression of miR-137 in NCSCs contributes to suppressing uncontrolled cell proliferation through the inhibition of DCLK1 expression.
The miR-137/DCLK1 axis as an important regulator in NCSCs and colon CSCs; further understanding of this axis may foster the development of potential gene therapeutic strategies targeting colon CSCs.
miRNA 在调节癌症干细胞（CSC）特性方面具有重要作用，被认为是潜在的治疗靶点。然而，很少有研究关注与结肠 CSCs 特别相关的 miRNA。本研究采用基于 PCR 的 miRNA 谱分析方法，对正常结肠干细胞（NCSC）和结肠 CSCs（EpCAM⁺/CD44⁺/CD66a⁻）进行分析，确定了调节结肠 CSC 特性的 miRNA。有趣的是，与 NCSCs 相比，miR-137（miR-137）在结肠 CSCs 中的表达下调，而双皮质激酶 1（DCLK1）mRNA 在结肠 CSCs 中高度表达，而在 NCSCs 中低表达。事实上，DCLK1 阳性癌细胞广泛分布于临床切除的结肠癌标本中，而 DCLK1 阳性上皮细胞在正常结肠组织中（包括隐窝底部）很少检测到。荧光素酶测定和免疫印迹分析显示，miR-137 调节 DCLK1 基因表达。外源性 miR-137 的转导抑制了体外结肠癌类器官的发育和体内结肠癌细胞的致瘤性，而不影响正常肠类器官的生长。此外，miR-137 的抑制增强了正常结肠细胞的类器官发育。这些数据表明，miR-137 具有抑制结肠 CSCs 致瘤性的能力，并且在 NCSCs 中维持 miR-137 的表达通过抑制 DCLK1 表达有助于抑制不受控制的细胞增殖。
miR-137/DCLK1 轴作为 NCSCs 和结肠 CSCs 中的重要调节因子；进一步了解该轴可能有助于开发针对结肠 CSCs 的潜在基因治疗策略。
