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

Abstract

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.

Epidermal Growth Factor–like Domain 7 Predicts Response to First-Line Chemotherapy and Bevacizumab in Patients with Metastatic Colorectal Cancer

“…When comparing EGFL7 and miR126 VA (adjacent sections), we detected a positive, significant relationship in biopsies and tumor resections, respectively, indicating some degree of common transcriptional regulation of miR126 and EGFL7. This is not surprising, because transcription of the EGFL7 gene also involves transcription of miR126 (22)(23)(24).…”

Micro RNA-126 coordinates cell behavior and signaling cascades according to characteristics of breast cancer cells

“…A reduction in SPRED-1 and PIK 3 R 2 levels is associated with increased expression of miR-126. When the impaired ERK phosphorylation can be salvaged by the blockade of SPRED-1, the damage in AKT phosphorylation-dependent VEGF may also be corrected through PIK 3 R 2 -blocked siRNA (38,42). It has been proposed that miR-126 specifi c for breast cancer targets VEGFA and PIK 3 R 2 , resulting in reduced activity of these gene locations (43).…”

miR-126 Suppresses the Proliferation of Cervical Cancer Cells and Alters Cell Sensitivity to the Chemotherapeutic Drug Bleomycin

“…miR-126 is relevant in many tumors, and studies have shown that miR-126 is significantly downregulated in gastric cancer tissues (Feng et al, 2010), non-small cell lung cancer cell lines (Zhu et al, 2012), prevalent diabetes mellitus (Zampetaki et al, 2010), cystic fibrosis airway epithelial cells (Oglesby et al, 2010), human breast cancer (Zhu et al, 2011), invasive ductal adenocarcinoma (Hamada et al, 2011), and cervical cancer tissues (Wang et al, 2008), as compared with relevant normal tissues. Using qRT-PCR analysis, we found that the expression of miR-126 in cervical cancer tissues was significantly decreased compare to that in normal cervical tissues, consistent with a previous report (Wang et al, 2008).…”

“…miR-126 has been reported to affect cancer progression through signaling pathways that control tumor cell proliferation, migration, invasion, and survival (Feng et al, 2010;Hamada et al, 2011;van Solingen et al, 2011;Zhu et al, 2011;Zhu et al, 2012). Some studies have also demonstrated that miR-126 has roles in regulating adhesion molecule expression (Harris et al, 2008), providing additional control of vascular inflammation (Harris et al, 2008), regulating the VEGF/PI3K/AKT signaling pathway (Hu et al, 2010), regulating the translation and invasiveness of vascular endothelial cell sprouting (Musiyenko et al, 2008), and governing the integrity and angiogenesis of the vasculature (Kuhnert et al, 2008;Wang et al, 2008b).…”

“…Previous studies have reported that miR-126 may play a role in tumorigenesis and growth by regulating the vascular endothelial growth factor (VEGF)/phosphoinositol 3-kinase (PI3K)/AKT signaling pathways in human breast cancer (Zhu et al, 2011). Additionally, this miRNA may function as a tumor suppressor, with Crk as a direct target, in gastric cancer (Feng et al, 2010) and via the regulation of ADAM9b in pancreatic cancer (Hamada et al, 2011).…”