Knockdown of insulin-like growth factor 1 receptor enhances chemosensitivity to cisplatin in human lung adenocarcinoma A549 cells

The effects of RNA interference-mediated insulin-like growth factor 1 receptor (IGF1R) gene silencing in response to cisplatin (DDP) in the lung cancer cell line A549 in vivo and in vitro were investigated using two plasmids expressing short hairpin RNA (shRNA) to IGF1R. A549 cells were transfected with plasmids expressing each shRNA and then treated with DDP. Semi-quantitative reverse transcription-PCR and Western blot analysis were used to detect the expression of IGF1R. MTT assay, flow cytometry and tumor growth assay in athymic nude mice were used to assess the chemosensitivity to DDP following IGF1R knockdown. Our data showed that the transfection of A549 cells with shRNA resulted in specific silencing of IGF1R by 78.9% at the mRNA level and by 89.8% at the protein level. Down-regulation of IGF1R significantly enhanced cell sensitivity to DDP, decreased the IC₅₀ of DDP in A549 cells at 24 h, 48 h and 72 h, and retained 77.5% of A549 cells in the G₀/G₁ phase. Furthermore, shRNA-mediated silencing of IGF1R in combination with DDP treatment enhanced the suppression of tumor growth in both size and weight by more than 60% and increased apoptosis by more than 75% when compared with the controls in vivo. Suppression of IGF1R gene expression by shRNA enhances the chemosensitivity of A549 cells to DDP both in vitro and in vivo, indicating the therapeutic potential of RNA interference as a method for gene therapy in treating lung cancer.