RT Journal Article SR Electronic T1 IGF1Ec Expression in MG-63 Human Osteoblast-like Osteosarcoma Cells JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 4259 OP 4265 VO 31 IS 12 A1 ANASTASSIOS PHILIPPOU A1 ATHANASIOS ARMAKOLAS A1 ZACHAROULA PANTELEAKOU A1 NIKOS PISSIMISSIS A1 ADRIANOS NEZOS A1 APOSTOLOS THEOS A1 MARIA KAPARELOU A1 NIKOS ARMAKOLAS A1 SPYRIDON G. PNEUMATICOS A1 MICHAEL KOUTSILIERIS YR 2011 UL http://ar.iiarjournals.org/content/31/12/4259.abstract AB Aim: 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. Materials and 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. Conclusion: 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.