Modulation Of Response To DDP Of Human Lung Cancer Following Insulin-like Growth Factor 1 Receptor Inaceivation

Objective:To study the effects of RNA interference (RNAi)-mediated IGF1R gene silencing on lung cancer cell line A549 and the enhancement of chemosensitivity in vivo and in vitro.Methods: two plasmids expressing siRNA for IGF-1R were constructed,and an unrelated siRNA was used as negative control.NSCLC cell lines A549 were transfected siRNA combine with DDP.Quantitative reverse-transcriptase PCR and Western blot were used to monitor the reduction in the production of IGF1R.MTT assay and flow cytometry in vitro and tumor growth assay in athymic nude mice in vivo were used to assess the enhancement of chemosensitivity flowing IGF1R silenced.IGF1R signaling pathways-associated proteins:total and phospho-ERK1/2 and Akt levels were detected by Western blot.Results: Our data showed transfection of NSCLC cells with siRNA resulted in sequence specific silencing of IGF1R with 78.9%in IGF1R mRNA transcription and 89.8%in protein production in A549 cells.Blunt Akt kinase and serum-induced Erk kinase activation.The decrease in IGF1R levels caused significant enhancement to DDP,decreased the IC₅₀of DDP to A549 cells both at 24h,48 h and at 72 h,and retained 77.5%A549 cellsin the G0/G1 phase.Furthermore,siRNA specific for IGF1R enhancement the suppression of DDP to tumor growth in vivo in size and in weight by more than 60%and in increased apoptosis by more than 75%.Conclusions:A new therapeutic effect of sequence specific suppression of IGF1R gene expression by RNAi enhances sensitivity to DDP in NSCLC cell both in vitro and in vivo were demonstrated,which support the therapeutic potential of RNAi as a method for gene therapy in treating lung cancer,and the IGF1R inhibition inducing chemosensitivity may be relate to the inhibition of ERK and Akt pathways activity.