Guan Xiaoqing, Gu Shucheng, Yuan Mu, Zheng Xiangxin, Wu Ji
Department of Breast Surgery, The Affiliated Suqian Hospital of Xuzhou Medical University, Suqian, Jiangsu 223800, P.R. China.
Oncol Lett. 2019 Dec;18(6):5986-5994. doi: 10.3892/ol.2019.10984. Epub 2019 Oct 14.
Drug resistance is a significant obstacle when treating triple-negative breast cancer (TNBC). Several studies have demonstrated that microRNAs (miRNAs) have essential roles in regulating drug resistance in different types of cancer. miR-33a-5p has previously been reported to be a tumor suppressor in several types of cancer. However, its role in breast cancer remains unknown. The present study aimed to investigate the role of miR-33a-5p in the chemoresistance of TNBC and uncover its potential molecular mechanisms. Cell Counting Kit-8 assay was used to examine cell proliferation, reverse transcription-quantitative PCR analysis was used to examine miR-33a levels, and western blotting and immunofluorescence assays were used to examine the expression of epithelial-mesenchymal transition (EMT)-associated proteins and of eukaryotic translation initiation factor 5A2 (eIF5A2). The results indicated that miR-33a-5p expression was lower in TNBC cells compared with non-TNBC cells. miR-33a-5p overexpression significantly improved the doxorubicin (Dox) sensitivity of TNBC cells, but not that of non-TNBC cells. It was then observed that Dox treatment inhibited miR-33a-5p expression and induced EMT in TNBC cells, by increasing the expression levels of vimentin, while decreasing the expression levels of E-cadherin. Furthermore, it was revealed that forced expression of miR-33a-5p attenuated Dox-induced EMT. eIF5A2 was identified as a potential target of miR-33a-5p, and miR-33a-5p overexpression inhibited the expression of eIF5A2. eIF5A2 inhibition, via its inhibitor GC7, sensitized TNBC cells to Dox and reversed Dox-induced EMT. Overall, the present study demonstrated that miR-33a-5p enhanced the sensitivity of TNBC cells to Dox, by suppressing eIF5A2 expression and reversing Dox-induced EMT, providing a potential therapeutic target for treating drug-resistant TNBC.
在治疗三阴性乳腺癌（TNBC）时，耐药性是一个重大障碍。多项研究表明，微小RNA（miRNA）在调节不同类型癌症的耐药性中起着重要作用。先前有报道称miR-33a-5p在几种类型的癌症中是一种肿瘤抑制因子。然而，其在乳腺癌中的作用仍不清楚。本研究旨在探讨miR-33a-5p在TNBC化疗耐药中的作用，并揭示其潜在的分子机制。采用细胞计数试剂盒-8法检测细胞增殖，采用逆转录-定量PCR分析检测miR-33a水平，采用蛋白质印迹法和免疫荧光法检测上皮-间质转化（EMT）相关蛋白和真核翻译起始因子5A2（eIF5A2）的表达。结果表明，与非TNBC细胞相比，TNBC细胞中miR-33a-5p表达较低。miR-33a-5p过表达显著提高了TNBC细胞对阿霉素（Dox）的敏感性，但对非TNBC细胞则没有。随后观察到，Dox处理通过增加波形蛋白的表达水平，同时降低E-钙黏蛋白的表达水平，抑制了TNBC细胞中miR-33a-5p的表达并诱导了EMT。此外，还发现miR-33a-5p的强制表达减弱了Dox诱导的EMT。eIF5A2被确定为miR-33a-5p的潜在靶点，miR-33a-5p过表达抑制了eIF5A2的表达。通过其抑制剂GC7抑制eIF5A2，使TNBC细胞对Dox敏感，并逆转了Dox诱导的EMT。总体而言，本研究表明，miR-33a-5p通过抑制eIF5A2表达和逆转Dox诱导的EMT，增强了TNBC细胞对Dox的敏感性，为治疗耐药性TNBC提供了一个潜在的治疗靶点。
