title: Silencing of a large microRNA cluster on human chromosome 14q32 in melanoma: biological effects of mir-376a and mir-376c on insulin growth factor 1 receptor.
abstract: BACKGROUND
  Metastatic melanoma is a devastating disease with limited therapeutic options. MicroRNAs (miRNAs) are small non coding RNA molecules with important roles in post-transcriptional gene expression regulation, whose aberrant expression has been implicated in cancer.
  
  
  RESULTS
  We show that the expression of miRNAs from a large cluster on human chromosome 14q32 is significantly down-regulated in melanoma cell lines, benign nevi and melanoma samples relative to normal melanocytes. This miRNA cluster resides within a parentally imprinted chromosomal region known to be important in development and differentiation. In some melanoma cell lines, a chromosomal deletion or loss-of-heterozygosity was observed in the cis-acting regulatory region of this cluster. In several cell lines we were able to re-express two maternally-induced genes and several miRNAs from the cluster with a combination of de-methylating agents and histone de-acetylase inhibitors, suggesting that epigenetic modifications take part in their silencing. Stable over-expression of mir-376a and mir-376c, two miRNAs from this cluster that could be re-expressed following epigenetic manipulation, led to modest growth retardation and to a significant decrease in migration in-vitro. Bioinformatic analysis predicted that both miRNAs could potentially target the 3'UTR of IGF1R. Indeed, stable expression of mir-376a and mir-376c in melanoma cells led to a decrease in IGF1R mRNA and protein, and a luciferase reporter assay indicated that the 3'UTR of IGF1R is a target of both mir-376a and mir-376c.
  
  
  CONCLUSIONS
  Our work is the first to show that the large miRNA cluster on chromosome 14q32 is silenced in melanoma. Our results suggest that down-regulation of mir-376a and mir-376c may contribute to IGF1R over-expression and to aberrant negative regulation of this signaling pathway in melanoma, thus promoting tumorigenesis and metastasis.
authors: Laboratory of Molecular Cell Biology, Cancer Research Center and Department of Medicine C, Sheba Medical Center, Tel Hashomer, Israel.
authors: Liron
authors: L
authors: Zehavi
authors: Roi
authors: R
authors: Avraham
authors: Aviv
authors: A
authors: Barzilai
authors: Dalia
authors: D
authors: Bar-Ilan
authors: Roy
authors: R
authors: Navon
authors: Yechezkel
authors: Y
authors: Sidi
authors: Dror
authors: D
authors: Avni
authors: Raya
authors: R
authors: Leibowitz-Amit
mesh_terms: D000107:Acetylation; D001483:Base Sequence; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D002883:Chromosomes, Human, Pair 14; D016000:Cluster Analysis; D056915:DNA Copy Number Variations; D057890:Epigenomics; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D023061:Gene Order; D020868:Gene Silencing; D018392:Genomic Imprinting; D006657:Histones / Q000378:metabolism; D006801:Humans; D008544:Melanocytes / Q000378:metabolism; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009506:Nevus / Q000235:genetics; D017526:Receptor, IGF Type 1 / Q000235:genetics*
chemical_list: D006657:Histones; C573498:MIRN376C microRNA, human; D035683:MicroRNAs; D017526:Receptor, IGF Type 1