Department of Surgery, Medical University of South Carolina, Charleston, SC 29425, USA; Hollings Cancer Center, Medical University of South Carolina, Charleston, SC 29425, USA.
Department of Surgery, Medical University of South Carolina, Charleston, SC 29425, USA.
Mol Ther. 2018 Mar 7;26(3):744-754. doi: 10.1016/j.ymthe.2017.12.023. Epub 2018 Jan 4.
Epithelial-to-mesenchymal transition (EMT) has been closely linked with therapy resistance and cancer stem cells (CSCs). However, EMT pathways have proven challenging to therapeutically target. MicroRNA 145 (miR-145) targets multiple stem cell transcription factors and its expression is inversely correlated with EMT. Therefore, we hypothesized that miR-145 represents a therapeutic target to reverse snail family transcriptional repressor 1 (SNAI1)-mediated stemness and radiation resistance (RT). Stable expression of SNAI1 in DLD1 and HCT116 cells (DLD1-SNAI1; HCT116-SNAI1) increased expression of Nanog and decreased miR-145 expression compared to control cells. Using a miR-145 luciferase reporter assay, we determined that ectopic SNAI1 expression significantly repressed the miR-145 promoter. DLD1-SNAI1 and HCT116-SNAI1 cells demonstrated decreased RT sensitivity and, conversely, miR-145 replacement significantly enhanced RT sensitivity. Of the five parental colon cancer cell lines, SW620 cells demonstrated relatively high endogenous SNAI1 and low miR-145 levels. In the SW620 cells, miR-145 replacement decreased CSC-related transcription factor expression, spheroid formation, and radiation resistance. In rectal cancer patient-derived xenografts, CSC identified by EpCAM+/aldehyde dehydrogenase (ALDH)+ demonstrated high expression of SNAI1, c-Myc, and Nanog compared with non-CSCs (EpCAM+/ALDH-). Conversely, patient-derived CSCs demonstrated low miR-145 expression levels relative to non-CSCs. These results suggest that the SNAI1:miR-145 pathway represents a novel therapeutic target in colorectal cancer to overcome RT resistance.
上皮-间充质转化 (EMT) 与治疗耐药性和癌症干细胞 (CSC) 密切相关。然而，EMT 途径在治疗上具有挑战性。microRNA 145 (miR-145) 靶向多个干细胞转录因子，其表达与 EMT 呈负相关。因此，我们假设 miR-145 代表一种治疗靶点，可逆转 snail 家族转录抑制因子 1 (SNAI1) 介导的干性和辐射抗性 (RT)。在 DLD1 和 HCT116 细胞 (DLD1-SNAI1；HCT116-SNAI1) 中稳定表达 SNAI1 与对照细胞相比，增加了 Nanog 的表达并降低了 miR-145 的表达。通过 miR-145 荧光素酶报告基因检测，我们确定外源性 SNAI1 表达显著抑制了 miR-145 启动子。DLD1-SNAI1 和 HCT116-SNAI1 细胞表现出对 RT 敏感性降低，相反，miR-145 替代显著增强了 RT 敏感性。在五个亲本结肠癌细胞系中，SW620 细胞表现出相对较高的内源性 SNAI1 和较低的 miR-145 水平。在 SW620 细胞中，miR-145 替代降低了 CSC 相关转录因子的表达、球体形成和辐射抗性。在直肠癌细胞来源的异种移植瘤中，EpCAM+/醛脱氢酶 (ALDH)+鉴定的 CSC 与非 CSC (EpCAM+/ALDH-) 相比，表现出高表达的 SNAI1、c-Myc 和 Nanog。相反，患者来源的 CSC 与非 CSC 相比，表现出低水平的 miR-145 表达。这些结果表明，SNAI1:miR-145 通路代表了克服 RT 耐药性的结直肠癌新的治疗靶点。
