Spermidine/spermine N-1-acetyltransferase (SSAT) is the key enzyme with regard to the maintenance of intracellular polyamine levels. It is an inducible enzyme, which may participate in adaptive responses to environmental stress. However, little is known regarding its responses to oxygen or nutrient deficiencies. Using, microarray assays, We discovered that SSAT was enhanced under both oxygen- and iron-deficient conditions. However. RT-PCR revealed that the SSAT mRNA was not induced: rather, an mRNA variant was newly expressed. In this variant, the splicing-in of 110 bases induces early termination, generating a truncated isoform which lacks catalytic motifs. The variant expression Occurs in other cancer cells and was irrelevant to both hypoxia-inducible factor 1 and to the redox state. We attempted to determine its role, using stable cell-lines. The expressed isoform was found to promote cell survival under iron-deficient conditions and blocked the cleavage of poly(ADP ribose) polymerase. This isoform may contribute to the progression or tumors of a more malignant phenotype under poor conditions and may constitute a potential target for anticancer therapy. © 2005 Elsevier Inc. All rights reserved.