title: Spermine oxidase SMO(PAOh1), Not N1-acetylpolyamine oxidase PAO, is the primary source of cytotoxic H2O2 in polyamine analogue-treated human breast cancer cell lines.
abstract: The induction of polyamine catabolism and its production of H2O2 have been implicated in the response to specific antitumor polyamine analogues. The original hypothesis was that analogue induction of the rate-limiting spermidine/spermine N1-acetyltransferase (SSAT) provided substrate for the peroxisomal acetylpolyamine oxidase (PAO), resulting in a decrease in polyamine pools through catabolism, oxidation, and excretion of acetylated polyamines and the production of toxic aldehydes and H2O2. However, the recent discovery of the inducible spermine oxidase SMO(PAOh1) suggested the possibility that the original hypothesis may be incomplete. To examine the role of the catabolic enzymes in the response of breast cancer cells to the polyamine analogue N1,N1-bis(ethyl)norspermine (BENSpm), a stable knockdown small interfering RNA strategy was used. BENSpm differentially induced SSAT and SMO(PAOh1) mRNA and activity in several breast cancer cell lines, whereas no N1-acetylpolyamine oxidase PAO mRNA or activity was detected. BENSpm treatment inhibited cell growth, decreased intracellular polyamine levels, and decreased ornithine decarboxylase activity in all cell lines examined. The stable knockdown of either SSAT or SMO(PAOh1) reduced the sensitivity of MDA-MB-231 cells to BENSpm, whereas double knockdown MDA-MB-231 cells were almost entirely resistant to the growth inhibitory effects of the analogue. Furthermore, the H2O2 produced through BENSpm-induced polyamine catabolism was found to be derived exclusively from SMO(PAOh1) activity and not through PAO activity on acetylated polyamines. These data suggested that SSAT and SMO(PAOh1) activities are the major mediators of the cellular response of breast tumor cells to BENSpm and that PAO plays little or no role in this response.
authors.affiliation: Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University, Baltimore, Maryland 21231, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Pledgie
authors.forename: Yi
authors.initials: Y
authors.lastname: Huang
authors.forename: Amy
authors.initials: A
authors.lastname: Hacker
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Woster
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Davidson
authors.forename: Robert A
authors.initials: RA
authors.lastname: Casero
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004396:Coloring Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism*; D020675:Peroxisomes / Q000378:metabolism; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism; D012313:RNA / Q000737:chemistry; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013096:Spermine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D000097667:Polyamine Oxidase; D000099228:Diamine N-Acetyltransferase
chemical_list: D000123:Acetyltransferases; D000970:Antineoplastic Agents; D004396:Coloring Agents; D006861:Hydrogen Peroxide; D000587:Oxidoreductases Acting on CH-NH Group Donors; D011073:Polyamines; D012313:RNA; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013096:Spermine; D013778:Tetrazolium Salts; D013844:Thiazoles; D000097667:Polyamine Oxidase; D000099228:Diamine N-Acetyltransferase; C059685:N(1),N(11)-diethylnorspermine; C501650:N(1)-acetylpolyamine oxidase, human; C022616:thiazolyl blue