Comparison of the abundance of 10 radiation-induced proteins with their differential gene expression in L929 cells

Purpose: To determine whether radiation-induced changes in protein abundance can be correlated with their differential gene expression in a murine fibroblast L929 cell line. Materials and methods: L929 cells were irradiated with 6 Gy. Cell lysates were collected at different points in time (20 min, 12, 24, 36, 48 and 72 h). The extracted proteins were separated by two-dimensional gel electrophoresis and quantified using computerized image analysis. Proteins exhibiting a differential expression equal to or more than twofold were identified by mass spectrometry following trypsin digestion. From these, 10 proteins characterized by large changes of radiation-induced abundance were selected in order to measure their corresponding gene expression using RTQ-PCR (real-time quantitative polymerase chain reaction). Results: Up to 15-fold changes in the abundance of these 10 proteins were associated with no detectable changes more than twofold on the gene expression level. However, one gene (VEGF-D) showed a significant (p = 0.005) up-regulation (1.8-fold). Conclusions: Deducing protein abundance from mRNA expression levels and vice versa appears to be of limited use. Furthermore, examination of transcriptional and translational changes provides different but complementary information.