The clinically relevant
polyamine analogue
N(1),N(11)-diethylnorspermine (
DENSPM) inhibits cell growth by down-regulating
polyamine biosynthesis, up-regulating
polyamine catabolism at the level of
spermidine/spermine N(1)-acetyltransferase (SSAT), and depleting intracellular
polyamine pools. Among human
melanoma cell lines, the analogue causes rapid apoptosis in SK-MEL-28 cells and a sharp G(1) arrest in MALME-3M cells. This study reveals that
DENSPM potently activates the
mitogen-activated protein kinase (MAPK) pathways in
melanoma cells and investigates the role of this response in determining cellular outcomes. Onset of apoptosis was preceded by an intense phosphorylation of the MAPKs, including
extracellular signal-regulated kinase 1/2, c-Jun NH(2)-terminal
kinase, and p38 in both SK-MEL-28 and MALME-3M cells. A panel of
DENSPM analogues differing only in their ability to induce SSAT was used to show that MAPK activation was causally linked to induction of SSAT activity and related oxidative events. The latter was confirmed with the
polyamine oxidase inhibitor MDL-75275 and the
antioxidant N-acetyl-L-cysteine, which when used in combination with
DENSPM, decreased MAPK activation and as previously shown, reduced apoptosis. The MAP/extracellular signal-regulated kinase-1 inhibitor
PD 98059 reduced activation of all three
kinases but failed to alter apoptosis in
DENSPM-treated SK-MEL-28 cells. By contrast, the inhibitor prevented p21(waf1/cip1) induction and enhanced apoptosis in MALME-3M cells as indicated by accelerated
caspase-3 activation and positive
annexin V staining. The generality of this effect was demonstrated in
DENSPM-treated A375 and LOX human
melanoma cells. Taken together, the importance of the MAPK pathways in determining the
biological response to
DENSPM treatment is dependent on the genetic environment of the cell.