Screening of Differentially Expressed Genes by Desferrioxamine or Ferric Ammonium Citrate Treatment in HepG2 Cells

A differential display method is used to identify novel genes whose expression is affected by treatment with ferric ammonium citrate (FAC) or desferrioxamine (DFO), an iron chelating agent in the human hepatoblastoma cell line (HepG2). These chemicals are known to deplete or increase the intracellular concentration of iron, respectively. Initially, we isolated seventeen genes whose expressions are down- or up regulated by the treatment of the chemicals, as well as their four differentially expressed genes that are designated as clone-1, -2, -3, and -4. These are further characterized by cDNA sequencing and Northern blot analysis. Through the cDNA sequencing, as well as comparing them to genes published using the NCBI BLAST program, we identified the sequence of the clone-1 that is up-regulated by the treatment of DFO. It is identical to the human insulin-like growth factor binding protein-1 (IGFBP-1). This suggests that the IGFBP-1 gene in the HepG2 cell is up-regulated by an iron depletion condition. Also, the expression of the clone-3 and -4 is up-regulated by FAC treatment and their eDNA sequences are identical to the human ferritin-fight chain and human NADH-dehydrogenase, respectively. However, the sequence of the clone-2 has no significant homology to any other known gene. Therefore, we suggest that changes of the cellular iron level in the HepG2 cell affects the transcription of cellular genes. This includes human IGFBP-1, ferritin-fight chain, and NADH-dehydrogenase. Regulation of these gene expressions may have an important role in cellular functions that are related to cellular iron metabolism.