Fig. 1

IGFBP3 enhanced IR-induced cell-killing in vitro. a Immunoblot analysis of IGFBP3 protein in OEC-M1 cells and TW2.6 cells with ectopic IGFBP3 expression (PB-IGFBP3) or vector control (PB) and in LN1–1 cells with IGFBP3 knockdown (IGFBP3 sh4 and sh5) and vector controls (pLKO-GFP). Protein levels were normalized to expression of α-tubulin, which served as an internal control. Relative ratios were determined by dividing the IGFBP3 protein level in each expression variant by that in the vector-expressing cells. b Effects of irradiation on survival and (c) colony formation of OEC-M1 and (d and e) TW2.6 cells with ectopic IGFBP3 expression versus vector controls and (f and g) LN1–1 cells with IGFBP3 knockdown and vector controls. Cells were treated with different doses of IR for viability and survival fraction using the MTS assay at 72 h and colony formation assay at 14 days after irradiation, respectively. The relative cell viability or survival fraction was normalized to corresponding untreated cells. Results from one of at least two independent experiments are shown. Values are expressed in mean ± SE. **p < 0.01; ***p < 0.001