title: IGF1Ec expression in MG-63 human osteoblast-like osteosarcoma cells.
abstract: OBJECTIVE
  The insulin-like growth factor 1 (IGF1) gene gives rise to multiple transcripts, using an elaborate alternative splicing mechanism. The aim of this study was to shed light on the expression and role of the IGF1 system in human MG-63 osteoblast-like osteosarcoma cells.
  
  
  METHODS
  The expression of the IGF1Ea, IGF1Eb and IGF1Ec isoforms was characterized using reverse transcription polymerase chain reaction (RT-PCR), quantitative real time-PCR (qRT-PCR) and western blot analysis. Using trypan blue exclusion assays, we also examined the mitogenic effects of IGF1 and of a synthetic peptide related to the E domain of IGF1Ec (synthetic E peptide) on MG-63 cells, as well as on MG-63 cells which had been molecularly modified to restrain the expression of type I IGF receptor (IGF1R) and of insulin receptor (INSR) by siRNA techniques (IGF1R KO or INSR KO MG-63 cells).
  
  
  RESULTS
  MG-63 cells express only the IGF1Ea and IGF1Ec transcripts. Exogenous administration of dihydrotestosterone (DHT) significantly increased the expression of IGF1Ea and IGF1Ec mRNA and it induced the previously undetectable expression of IGF1Eb transcript. Exogenous administration of IGF1, insulin and the synthetic E peptide stimulated the growth of MG-63 cells, while only E peptide stimulated the growth of IGF1R KO and INSR KO MG-63 cells.
  
  
  CONCLUSIONS
  These data suggest that the expression of all IGF1 isoforms is hormonally regulated in MG-63 cells and that the expression of IGF1Ec may be involved in osteosarcoma biology by generating the Ec peptide which acts via an IGF1R-independent and INSR-independent mechanism.
authors.affiliation: Department of Experimental Physiology, Medical School, National & Kapodistrian University of Athens, 75 Micras Asias, Goudi-Athens 11527, Greece.
authors.forename: Anastassios
authors.initials: A
authors.lastname: Philippou
authors.forename: Athanasios
authors.initials: A
authors.lastname: Armakolas
authors.forename: Zacharoula
authors.initials: Z
authors.lastname: Panteleakou
authors.forename: Nikos
authors.initials: N
authors.lastname: Pissimissis
authors.forename: Adrianos
authors.initials: A
authors.lastname: Nezos
authors.forename: Apostolos
authors.initials: A
authors.lastname: Theos
authors.forename: Maria
authors.initials: M
authors.lastname: Kaparelou
authors.forename: Nikos
authors.initials: N
authors.lastname: Armakolas
authors.forename: Spyridon G
authors.initials: SG
authors.lastname: Pneumaticos
authors.forename: Michael
authors.initials: M
authors.lastname: Koutsilieris
mesh_terms: D017398:Alternative Splicing; D045744:Cell Line, Tumor; D020869:Gene Expression Profiling / Q000379:methods; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008954:Models, Biological; D010006:Osteoblasts / Q000378:metabolism; D012516:Osteosarcoma / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D020033:Protein Isoforms; D034741:RNA, Small Interfering / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D011972:Receptor, Insulin / Q000096:biosynthesis; D019076:Transgenes
chemical_list: D010455:Peptides; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D007334:Insulin-Like Growth Factor I; D011972:Receptor, Insulin