Transcriptional profiling identifies altered intracellular labile iron homeostasis as a contributing factor to the toxicity of adaphostin: decreased vascular endothelial growth factor secretion is independent of hypoxia-inducible factor-1 regulation.
OBJECTIVE
Adaphostin was developed as an inhibitor of the p210(bcr-abl) tyrosine kinase, but as its activity is not limited to tumor cell lines containing this translocation, transcriptional profiling was used as a tool to elucidate additional mechanisms responsible for adaphostin cytotoxicity.


METHODS
Profiles of drug-induced transcriptional changes were measured in three hematopoietic cell lines following 1 and 10 micromol/L adaphostin for 2 to 6 hours and then confirmed with real-time reverse transcription-PCR (2-24 hours). These data indicated altered iron homeostasis, and this was confirmed experimentally. Alteration of vascular endothelial growth factor (VEGF) secretion through hypoxia-inducible factor-1 (HIF-1) regulation was also investigated.


RESULTS
Drug-induced genes included heat shock proteins and ubiquitins, but an intriguing response was the induction of ferritins. Measurement of the labile iron pool showed release of chelatable iron immediately after treatment with adaphostin and was quenched with the addition of an iron chelator. Pretreatment of cells with desferrioxamine and N-acetyl-cysteine reduced but did not ablate the sensitivity of the cells to adaphostin, and desferrioxamine was able to modulate adaphostin-induced activation of p38 and inactivation of AKT. VEGF secretion was shown to be reduced in cell lines after the addition of adaphostin but was not dependent on HIF-1.


CONCLUSIONS
Adaphostin-induced cytotoxicity is caused in part by a rapid release of free iron, leading to redox perturbations and cell death. Despite this, reduced VEGF secretion was found to be independent of regulation by the redox responsive transcription factor HIF-1. Thus, adaphostin remains an interesting agent with the ability to kill tumor cells directly and modulate angiogenesis.
Hose
Curtis
C
SAIC Frederick, Inc., Screening Technologies Branch, Laboratory of Functional Genomics, National Cancer Institute Frederick, Frederick, Maryland 21702, USA.
Kaur
Gurmeet
G
Sausville
Edward A
EA
Monks
Anne
A
D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D015687:Cell Hypoxia; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004338:Drug Combinations; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D018922:HL-60 Cells; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D019169:Jurkat Cells; D020014:K562 Cells; D015394:Molecular Structure; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011990:Receptors, Transferrin / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D000975:Antioxidants; D017077:Culture Media, Conditioned; D004338:Drug Combinations; C497442:HIF1A protein, human; D006873:Hydroquinones; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007502:Iron Chelating Agents; C404397:NSC 680410; D012333:RNA, Messenger; D011990:Receptors, Transferrin; D014157:Transcription Factors; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D007501:Iron; D000218:Adamantane