Metabolic and Antiproliferative Consequences of Activated Polyamine Catabolism in LNCaP Prostate Carcinoma Cells

• Published in: The Journal of biological chemistry Vol. 279; no. 26; pp. 27050 - 27058
• Main Authors: Kee, Kristin, Vujcic, Slavoljub, Merali, Salim, Diegelman, Paula, Kisiel, Nicholas, Powell, C. Thomas, Kramer, Debora L., Porter, Carl W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 25.06.2004; American Society for Biochemistry and Molecular Biology
• Subjects: Acetyl Coenzyme A - metabolism; Acetyltransferases - genetics; Acetyltransferases - metabolism; Adenosylmethionine Decarboxylase - metabolism; Carcinoma - enzymology; Carcinoma - metabolism; Carcinoma - pathology; Cell Division - drug effects; Cell Division - physiology; Deoxyadenosines - metabolism; Eflornithine - pharmacology; Enzyme Inhibitors - pharmacology; Humans; Male; Methionine - pharmacology; Ornithine - pharmacology; Ornithine Decarboxylase - metabolism; Ornithine Decarboxylase Inhibitors; Oxidoreductases Acting on CH-NH Group Donors - antagonists & inhibitors; Polyamine Oxidase; Polyamines - chemistry; Polyamines - metabolism; Prostatic Neoplasms - enzymology; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - pathology; Putrescine - analogs & derivatives; Putrescine - pharmacology; RNA, Messenger - biosynthesis; S-Adenosylmethionine - analogs & derivatives; S-Adenosylmethionine - metabolism; Tetracyclines - pharmacology; Thionucleosides - metabolism; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M403323200

Depletion of intracellular polyamine pools invariably inhibits cell growth. Although this is usually accomplished by inhibiting polyamine biosynthesis, we reasoned that this might be more effectively achieved by activation of polyamine catabolism at the level of spermidine/spermine N1-acetyltransferase (SSAT); a strategy first validated in MCF-7 breast carcinoma cells. We now examine the possibility that, due to unique aspects of polyamine homeostasis in the prostate gland, tumor cells derived from it may be particularly sensitive to activated polyamine catabolism. Thus, SSAT was conditionally overexpressed in LNCaP prostate carcinoma cells via a tetracycline-regulatable (Tet-off) system. Tetracycline removal resulted in a rapid ∼10-fold increase in SSAT mRNA and an increase of ∼20-fold in enzyme activity. SSAT products N1-acetylspermidine, N1-acetylspermine, and N1,N12-diacetylspermine accumulated intracellularly and extracellularly. SSAT induction also led to a growth inhibition that was not accompanied by polyamine pool depletion as it was in MCF-7 cells. Rather, intracellular spermidine and spermine pools were maintained at or above control levels by a robust compensatory increase in ornithine decarboxylase and S-adenosylmethionine decarboxylase activities. This, in turn, gave rise to a high rate of metabolic flux through both the biosynthetic and catabolic arms of polyamine metabolism. Treatment with the biosynthesis inhibitor α-difluoromethylornithine during tetracycline removal interrupted flux and prevented growth inhibition. Thus, flux-induced growth inhibition appears to derive from overaccumulation of metabolic products and/or from depletion of metabolic precursors. Metabolic effects that were not excluded as possible contributing factors include high levels of putrescine and acetylated polyamines, a 50% reduction in S-adenosylmethionine, and a 45% decline in the SSAT cofactor acetyl-CoA. Overall, the study demonstrates that activation of polyamine catabolism in LNCaP cells elicits a compensatory increase in polyamine biosynthesis and downstream metabolic events that culminate in growth inhibition.