Screening of transcriptionally regulated genes following iron chelation in human astrocytoma cells

Deferoxamine is an effective iron chelator and a potential therapeutic agent for use in minimizing free radical-mediated injury following trauma. Iron chelation may also be an effective means of limiting tumor growth by decreasing bioavailable iron. Deferoxamine can modulate gene expression through manipulation of intracellular iron levels; specifically at the posttranscription level by changing the activity of iron regulatory proteins (IRPs). The effect of iron chelation on the transcription of genes is still unclear, but iron-binding sites on DNA have been reported. Here we investigate the influence of deferoxamine on gene transcription. Two-directional (forward and backward) suppression subtraction hybridization (SSH) was performed on human astrocytoma cells (SW1088) cultured in either standard media or treated for 48 hours with deferoxamine. To restrict the number of false-positive clones, reverse Northern blotting was used to further verify the differentially expressed cDNA clones. Positive clones were sequenced and the mRNAs were re-examined on Northern blots for changes in expression over time of deferoxamine exposure. The results of these analyses have identified both novel and known genes whose expression is influenced by iron chelation. The known genes include a group related to energy production and a group related to protease function. These results provide examples of genes not previously known to be directly influenced by iron availability, and as such may be potential targets for iron chelation therapy.