Endothelial-specific intron-derived miR-126 is down-regulated in human breast cancer and targets both VEGFA and PIK3R2

• DOI: 10.1007/s11010-011-0723-7
• Publication Date: 2011-01-19T01:15:29Z
• Authors: Ni Zhu; Dongze Zhang; Haoping Xie; Zhe Zhou; Huyan Chen; Tiantian Hu; Yuan Bai; Yuan Shen; Wenjun Yuan; Qing Jing; Yongwen Qin
• Keywords: Male; Vascular Endothelial Growth Factor A; 0301 basic medicine; Base Sequence; Down-Regulation; Breast Neoplasms; Polymerase Chain Reaction; Introns; Rats; 3. Good health; Rats, Sprague-Dawley; MicroRNAs; Phosphatidylinositol 3-Kinases; 03 medical and health sciences; Animals; Humans; Female; Endothelium, Vascular; Cells, Cultured; DNA Primers; Signal Transduction

Endothelial cells are the key components of vascular intima and play pivotal roles in vasculogenesis, angiogenesis, and tumor growth. Using Northern blot and real-time PCR, we confirmed that miR-126 and its host gene EGF-like domain 7 (EGFL7) were widely expressed in rat tissues but strictly expressed in endothelial cells. In mammals, miR-126 gene is embedded in intron7 of EGFL7. To explore the biogenesis of miR-126, plasmid EGFL7(126)-pEGFPc1 containing segment of exon7-intron7-exon8 of EGFL7 was constructed and expressed in 293T. Expression of spliced exon7-8 and excised mature miR-126 was detected by PCR and Northern blot. Knocking-down of endothelial endogenous miR-126 did not affect EGFL7 expression at mRNA or protein level. To investigate the possible roles of miR-126, PicTar, miRBase, miRanda, Bibiserv, and Targetscan were used to screen the targets. VEGFA and PIK3R2 were confirmed as the targets of miR-126 by luciferase reporter assay and Western blot. Interestingly, Northern blot and western blot showed that miR-126 was down-regulated in breast tumors where the VEGF/PI3K/AKT signaling pathway was activated. Introduction of miR-126 mimics into MCF-7 could effectively decrease VEGF/PI3K/AKT signaling activity. In summary, miR-126 was strictly expressed in endothelial cells and excised from EGFL7 pre-mRNA without affecting splicing and expression of its host gene. In addition, miR-126 could target both VEGFA and PIK3R2, and its expression was decreased in human breast cancer, implying that miR-126 may play a role in tumor genesis and growth by regulating the VEGF/PI3K/AKT signaling pathway.