Xie Xiaohong, Hu Yuanyuan, Xu Leilai, Fu Yongqing, Tu Jue, Zhao Hong, Zhang Shuo, Hong Ri, Gu Xidong
Department of Breast Surgery, First Affiliated Hospital of Zhejiang Chinese Medical University, Youdian Road 54#, Shangcheng District, Hangzhou City, 310006, Zhejiang Province, China.
Tumour Biol. 2015 Sep;36(9):7185-94. doi: 10.1007/s13277-015-3438-7. Epub 2015 Apr 17.
MicroRNAs (miRNAs) are a class of naturally occurring, small, non-coding RNAs which play important roles in diverse biological processes and are acting as key regulators of tumorigenesis and chemotherapy resistance. In this study, a downregulation of miR-125b was observed in breast cancer cell lines, suggesting miR-125b is a tumor suppressor in breast cancer. Moreover, the miR-125b levels were significantly decreased in doxorubicin-resistant MCF-7 (MCF-7/DR) cells compared with MCF-7 cells. Transfection of miR-125b significantly enhanced the cytotoxicity of doxorubicin to MCF-7/DR cells. However, the overexpression of miR-125b did not influence the doxorubicin accumulation but downregulated the myeloid cell leukemia-1 (Mcl-1) levels, which may be the mechanism of apoptosis induction caused by doxorubicin combining with miR-125b in MCF-7/DR cells. Furthermore, luciferase reporter assay proved that Mcl-1 is the target of miR-125b. Importantly, we found that the sensitization of miR-125b to doxorubicin cytotoxicity is caspase-dependent in MCF-7/DR cells, which can be inhibited by zVAD-fmk. Finally, we indicated that the treatment of miR-125b plus doxorubicin leads to loss of mitochondrial membrane potential (MMP) and mitochondria outer membrane permeability (MOMP), which were interacted with the activation of caspases. Thus, this study revealed the role of miR-125b in doxorubicin resistance and therapy, which may provide novel approaches for the treatment of breast cancer.
微小RNA（miRNA）是一类天然存在的小的非编码RNA，在多种生物学过程中发挥重要作用，并且是肿瘤发生和化疗耐药的关键调节因子。在本研究中，在乳腺癌细胞系中观察到miR-125b表达下调，提示miR-125b是乳腺癌中的一种肿瘤抑制因子。此外，与MCF-7细胞相比，阿霉素耐药的MCF-7（MCF-7/DR）细胞中miR-125b水平显著降低。转染miR-125b可显著增强阿霉素对MCF-7/DR细胞的细胞毒性。然而，miR-125b的过表达并不影响阿霉素的蓄积，但下调了髓样细胞白血病-1（Mcl-1）水平，这可能是阿霉素与miR-125b联合诱导MCF-7/DR细胞凋亡的机制。此外，荧光素酶报告基因检测证明Mcl-1是miR-125b的靶标。重要的是，我们发现在MCF-7/DR细胞中，miR-125b对阿霉素细胞毒性的致敏作用是半胱天冬酶依赖性的，可被zVAD-fmk抑制。最后，我们指出miR-125b加阿霉素治疗导致线粒体膜电位（MMP）丧失和线粒体外膜通透性（MOMP）改变，这与半胱天冬酶的激活相互作用。因此，本研究揭示了miR-125b在阿霉素耐药和治疗中的作用，可能为乳腺癌治疗提供新的方法。
