College of Life Sciences, Qufu Normal University, Qufu, 273165, Shandong, China.
Cell Mol Biol Lett. 2022 Oct 9;27(1):88. doi: 10.1186/s11658-022-00393-x.
Current studies show that exosomal miRNAs become an important factor in cancer metastasis. Among the many miRNA studies, miR-7-5p has not been thoroughly investigated in breast cancer metastasis.
Bioinformatic screening was performed using extant data from the GEO database, and miR-7-5p expression levels in breast cancer cell lines and exosomes were further examined using real-time quantitative PCR (qRT-PCR). The extracted exosomes were characterised by transmission electron microscopy (TEM), particle size analysis and marker protein determination. Cell migration and invasion were then examined using wound healing assays and Transwell assays, respectively. Correlation between miR-7-5p and receptor-like tyrosine kinase (RYK) was analysed by luciferase reporter. The effect of miR-7-5p against RYK-related downstream factors was verified using western blot assays.
In this study, we found that the expression of miR-7-5p was significantly different in exosomes secreted from breast cancer cell lines with different high and low invasiveness. Further experiments revealed that miR-7-5p has an important role in inhibiting the migration and invasion of breast cancer. In terms of mechanism of action, miR-7-5p was found to target the RYK, leading to its reduced expression, which in turn caused a reduction in the phosphorylation level of the downstream factor JNK. Reduced levels of phosphorylated JNK factors lead to reduced levels of phosphorylation of c-Jun protein, which in turn leads to increased expression of EMT transcription factors, thereby inhibiting the epithelial-mesenchymal transition (EMT) process to suppress the invasion of breast cancer.
Thus, we demonstrated that exosomes loaded with high levels of miR-7-5p emitted from less aggressive breast cancers can participate in the atypical WNT pathway by targeting the RYK gene and thus inhibit breast cancer metastasis.
目前的研究表明，外泌体中的 miRNAs 成为癌症转移的一个重要因素。在众多 miRNA 研究中，miR-7-5p 在乳腺癌转移中的研究还不够深入。
利用 GEO 数据库中的现有数据进行生物信息学筛选，并通过实时定量 PCR（qRT-PCR）进一步检测乳腺癌细胞系和外泌体中的 miR-7-5p 表达水平。通过透射电子显微镜（TEM）、颗粒大小分析和标记蛋白测定来表征提取的外泌体。然后分别通过划痕愈合实验和 Transwell 实验检测细胞迁移和侵袭。通过荧光素酶报告分析 miR-7-5p 与受体样酪氨酸激酶（RYK）之间的相关性。通过 Western blot 实验验证 miR-7-5p 对 RYK 相关下游因子的作用。
在这项研究中，我们发现具有不同高侵袭性和低侵袭性的乳腺癌细胞系分泌的外泌体中 miR-7-5p 的表达有显著差异。进一步的实验表明，miR-7-5p 在抑制乳腺癌的迁移和侵袭中起着重要作用。就作用机制而言，发现 miR-7-5p 靶向 RYK，导致其表达减少，进而导致下游因子 JNK 的磷酸化水平降低。磷酸化 JNK 因子水平降低导致 c-Jun 蛋白磷酸化水平降低，进而导致 EMT 转录因子表达增加，从而抑制乳腺癌的上皮-间充质转化（EMT）过程，抑制乳腺癌的侵袭。
因此，我们证明了来自侵袭性较低的乳腺癌的富含 miR-7-5p 的外泌体可以通过靶向 RYK 基因参与非典型 WNT 途径，从而抑制乳腺癌转移。
