TY - JOUR T1 - Small Interfering RNA Suppression of Polyamine Analog-Induced Spermidine/Spermine <em>N</em><sup>1</sup>-Acetyltransferase JF - Molecular Pharmacology JO - Mol Pharmacol SP - 1153 LP - 1159 DO - 10.1124/mol.64.5.1153 VL - 64 IS - 5 AU - Ying Chen AU - Debora L. Kramer AU - Jason Jell AU - Slavoljub Vujcic AU - Carl W. Porter Y1 - 2003/11/01 UR - http://molpharm.aspetjournals.org/content/64/5/1153.abstract N2 - N1,N11-diethylnorspermine (DENSPM) is a polyamine analog that down-regulates polyamine biosynthesis and potently upregulates the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase (SSAT). In certain cells, such as SKMEL-28 human melanoma cells, induction of SSAT is associated with rapid apoptosis. In this study, we used small interfering RNA (siRNA) to examine the role of SSAT induction in mediating polyamine pool depletion and apoptosis. siRNA duplexes were designed to target three independent sites in the SSAT mRNA coding region (siSSAT). When transfected under nontoxic conditions, two of the duplexes selectively reduced basal SSAT mRNA in HEK-293 cells by &gt;80% and prevented DENSPM-induced SSAT mRNA by 95% in SK-MEL-28 cells. Treatment of SK-MEL-28 cells with 10 μM DENSPM in the presence of 83 nM siSSAT selectively prevented the 1400-fold induction of SSAT activity by ∼90% and, in turn, prevented analog depletion of spermine (Spm) pools by ∼35%. siSSAT also prevented DENSPM-induced cytochrome c release and caspase-3 cleavage at 36 h and apoptosis at 48 h as measured by annexin V staining. Overall, the data directly link analog induction of SSAT to Spm pool depletion and to caspase-dependent apoptosis in DENSPM-treated SK-MEL-28 cells. This represents the first use of siRNA technology directed toward a polyamine gene and the first unequivocal demonstration that SSAT induction initiates events leading to polyamine analog-induced apoptosis. ER -