Altered expression of zinc finger proteins, ADAMs, and integrin‐related proteins following treatment of cultured human cells with a low concentration of N‐methyl‐N′‐nitro‐N‐nitrosoguanidine

Proteomic analysis is an important approach to characterize the proteome and study protein functions. It is also a powerful screening method for detecting unexpected alterations in protein expression that may be overlooked by conventional biochemical techniques. N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) is an alkylating agent that can induce nontargeted mutagenesis in treated cells, although the mechanism remains unclear. Using an efficient proteomic method, we identified several cellular proteins that are responsive to low-concentration MNNG treatment in human FL cells. After MNNG treatment, whole cellular proteins were separated using two-dimensional gel electrophoresis and visualized by silver staining; the digitized images then were analyzed with 2D analysis software. More than 60 proteins showed significant changes in MNNG-treated cells compared to control cells (DMSO treatment). Thirty-one proteins only detected in MNNG-treated or control cells were subjected to in-gel digestion with trypsin and identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry using peptide mass fingerprinting. Eighteen of theses proteins have been identified, including several zinc finger proteins, two members of the ADAMs (a disintegrin and metalloprotease domain) family, and two integrins. Most of these proteins have unknown functions and their involvement in the cellular responses to alkylating agents have not been reported. Therefore, our findings may offer new insights into the mechanisms of low-concentration MNNG-induced nontargeted mutagenesis and these proteins may serve as new biomarkers for detecting exposure of human populations to environmental carcinogens.