miR-660-5p promotes breast cancer progression through down-regulating TET2 and activating PI3K/AKT/mTOR signaling

Breast cancer (BC) is a commonly diagnosed cancer in females. MicroRNA-660-5p (miR-660-5p) has been reported to be involved in the occurrence and development of BC. However, the regulatory network of miR-660-5p in BC has not been fully addressed. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the enrichment of miR-660-5p and tet-eleven translocation 2 (TET2) in BC tissues and cells. Cell counting kit-8 (CCK8), flow cytometry, and transwell migration and invasion assays were used to measure cell proliferation, apoptosis, migration, and invasion. The target relationship between miR-660-5p and TET2 was confirmed by dual luciferase reporter assay. Protein expression was measured by western blot. The expression of miR-660-5p was elevated in BC, and high expression of miR-660-5p was closely related to lymph node metastasis, advanced TNM stage, and vascular invasion of BC tumors. miR-660-5p silencing inhibited cell proliferation and metastasis, but induced apoptosis of BC cells. TET2 was identified as a direct target of miR-660-5p, and the interference of TET2 partly reversed the suppressive effects of miR-660-5p silencing on the malignant potential of BC cells. miR-660-5p promoted BC progression partly through modulating TET2 and PI3K/AKT/mTOR signaling. miR-660-5p/TET2 axis might be a promising target for BC treatment.

乳腺癌（Breast cancer, BC）是女性群体中确诊率较高的癌症类型。已有研究证实，微小RNA-660-5p（MicroRNA-660-5p, miR-660-5p）参与乳腺癌的发生与发展过程，但miR-660-5p在乳腺癌中的调控网络尚未得到全面阐释。本研究采用实时荧光定量聚合酶链式反应（Quantitative real-time polymerase chain reaction, qRT-PCR）检测miR-660-5p与十-十一易位酶2（tet-eleven translocation 2, TET2）在乳腺癌组织及细胞中的表达水平；通过细胞计数试剂盒-8（Cell counting kit-8, CCK8）、流式细胞术、Transwell迁移与侵袭实验分别评估细胞增殖、凋亡、迁移及侵袭能力；借助双荧光素酶报告基因实验验证miR-660-5p与TET2的靶向调控关系；采用蛋白质印迹法（Western blot）检测相关蛋白的表达情况。实验结果表明，miR-660-5p在乳腺癌组织中呈高表达状态，且其高表达与乳腺癌患者的淋巴结转移、晚期TNM分期及肿瘤血管侵犯显著相关。沉默miR-660-5p可抑制乳腺癌细胞的增殖与转移能力，并诱导细胞凋亡。研究证实TET2是miR-660-5p的直接靶基因，而敲低TET2可部分逆转miR-660-5p沉默对乳腺癌细胞恶性潜能的抑制作用。进一步研究发现，miR-660-5p可通过调控TET2及PI3K/AKT/mTOR信号通路部分促进乳腺癌的进展。综上，miR-660-5p/TET2轴有望成为乳腺癌治疗的潜在靶点。