Genome-wide screening of temporal responsive genes induced by a low concentration of the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine in a normal human cell line

The alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is a direct mutagen and carcinogen, causing DNA damage and other comprehensive alterations that lead to chromosomal aberrations, mutations, tumor initiation, and cell death. Our previous study revealed that MNNG at different concentrations could induce extensive changes in gene expression at an early stage of exposure. To further understand the dynamic cellular responses and hazardous effects caused by this environmental carcinogen, we used a whole-genome time-course screening methods to find out the gene expression changes induced by a low concentration of MNNG in human normal amnion epithelial FL cells. The cells were exposed to 1.0 M MNNG, and differential gene expression profiles at 3, 12, and 24 h after MNNG treatment were obtained by use of Affymetrix HG-U133 Plus 2.0 oligonucleotide microarray technology, followed by quantitative real-time RT-PCR validation. The results showed that the low-dose MNNG exposure triggered extensive but moderate changes in gene expression at these three experiment time points after exposure. The responsive genes encode important proteins, including cell cycle regulators, transcription factors and signal transducers that determine cell cycle progression, cell fate and other activities associate with pro-oncogenic potentials. The differential gene expression profiles at the three time points varied greatly, and generally reflected a cellular responsive process from initiation to progression and to recovery after MNNG exposure. These results will aid our understanding of the complicated mechanisms of MNNG-induced cellular responses.

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