MicroRNA-378 promotes cell survival, tumor growth, and angiogenesis by targeting SuFu and Fus-1 expression

Abstract

MicroRNAs are single-stranded RNA of 18 -24 nt expressed endogenously that play important roles in cancer development. Here, we show that expression of miR-378 enhances cell survival, reduces caspase-3 activity, and promotes tumor growth and angiogenesis. Proteomic analysis indicates reduced expression of suppressor of fused (Sufu), a potential target of miR-378, which was confirmed in vitro and in vivo. Expression of a luciferase construct containing the target site in Sufu was repressed when cotransfected with miR-378. Transfection of a Sufu construct reversed the effect of miR-378, suggesting an important role for miR-378 in tumor cell survival. We also discovered that miR-378 targets Fus-1. Expression of luciferase constructs harboring the target sites in Fus-1 was repressed by miR-378. Fus-1 constructs with or without its 3 UTR were also generated. Cotransfection experiments showed that the presence of miR-378 repressed Fus-1 expression. Suppression of Fus-1 expression by siRNA against Fus-1 enhanced cell survival. Transfection of the Fus-1 construct reversed the function of miR-378 in cell survival. Our results suggest that miR-378 transfection enhanced cell survival, tumor growth, and angiogenesis through repression of the expression of two tumor suppressors, Sufu and Fus-1.miRNA ͉ oncogenic miRNA ͉ tumorigenesis O ver the past few years, microRNAs (miRNAs) have emerged as a prominent class of gene regulators (1). miRNAs are single-stranded RNA of 18-24 nt in length and are generated by an RNase III-type enzyme from an endogenous transcript that contains a local hairpin structure (2, 3). miRNA functions as a guide molecule in posttranscriptional gene silencing by partially complementing with the 3Ј untranslated region (UTR) of the target mRNAs, leading to translational repression (4). In animals, miRNA genes are transcribed to generate long primary transcripts, which are processed by the RNase III-type enzyme Drosha to produce precursor miRNAs (premiRNAs) in the nucleus (5). PremiRNAs are then exported to the cytoplasm by exportin-5 (6). After arrival in the cytoplasm, premiRNAs are subjected to secondary processing by Dicer, a cytoplasmic RNase III-type enzyme (7,8). miRNAs normally repress gene expression, opposing the activity of transcription factors, which initiate gene expression (9). By silencing various target mRNAs, miRNAs have key roles in diverse regulatory pathways, including control of development (10), cell differentiation (11), apoptosis (12-14), cell proliferation (15), division (16), protein secretion (17), and viral infection (18,19). Most importantly, miRNAs have been known to play roles in cancer development (20)(21)(22)(23). Previous studies have shown that miR-378 is expressed in a number of cancer cell lines (24) and is involved in the expression of vascular endothelial growth factor (25). To understand the biological functions of miR-378, we have generated a miR-378 expression construct for functional studies. Here, we show that stable expression of miR-378 plays a role in cell sur...

A Novel Cardiomyocyte-enriched MicroRNA, miR-378, Targets Insulin-like Growth Factor 1 Receptor

“…Previously, in carcinoma cell lines U87 and MT-1, as well as in pooled cells, transfection of the 378-pre-miR hairpin was reported to promote tumor growth and angiogenesis. This study showed the miR-378* seed sequence (addressed in this report as miR-378) targets transcription factors SuFu and Fus-1 (22) and promotes cell survival, whereas in our study we observed an apoptosisinducing role of miR-378 in cardiomyocytes. Additionally, miR-378* has been shown to promote a metabolic switch from OXPHOS to glycolysis in the BT-474 breast cancer cell line (20).…”

Identification of microRNAs associated with hyperthermia-induced cellular stress response

“…Of the 55 putative targets, we found that only eight have been empirically validated: miR-378-SUFU, miR-101- MYCN,, and let-7c-TRIM71 (Lewis et al 2003(Lewis et al , 2005Yekta et al 2004;Lee et al 2007;Lin et al 2007;Mitomo et al 2008). Interestingly, many of the 47 remaining putative targets have known CSR functions: proteolysis (miR-101-UBE2A); molecular chaperones (miR-125b-DNAJB2, miR-424-HSPA4L, miR-424-DNAJB4, miR-125b-TTC7A, miR-452-TTC7A, miR-378-TTC7A, miR-378-HSP90AB1, miR-138-CCT5, miR-138-HSPA4L, miR-376a-HSPA6, miR-let-7c-HSPB2, and miR-196a-HSPH1) (Kojima et al 2004;White et al 2005); protein trafficking (miR-125-ZFYVE1); metabolism (miR-382-KYNU, miR-378-KLK4, miR-376a-MAN1C1, miR-let-7c-GALE, and miR-let-7c-RNF20); cell cycle progression (miR-101-MYCN, miR-196a-HOXC8, and miR-196b-HOXC8) (Deraison et al 2007;Kamel et al 2009) (Tables 1 and 2).…”

Distinctive microRNA expression profiles in CD34+ bone marrow cells from patients with myelodysplastic syndrome

“…This miRNA promotes cell survival, tumor growth and angiogenesis by targeting SUFU gene expression. 18 Our previously published gene expression data 11 showed an increase of SUFU transcript level in 5qÀ syndrome patients. Another putative target of miR-378 is transcription factor ETV6.…”