title: The role of the polyamine catabolic enzymes SSAT and SMO in the synergistic effects of standard chemotherapeutic agents with a polyamine analogue in human breast cancer cell lines.
abstract: BACKGROUND
  Polyamine analogues have demonstrated significant activity against human breast cancer cell lines as single agents as well as in combination with other cytotoxic drugs. This study evaluates the ability of a polyamine analogue N (1),N (11)-bis(ethyl)norspermine (BENSpm) to synergize with six standard chemotherapeutic agents, 5-fluorouracil (FU), fluorodeoxyuridine, cis-diaminechloroplatinum(II) (C-DDP), paclitaxel, docetaxel, and vinorelbine.
  
  
  METHODS
  Four human breast cancer cell lines (MDA-MB-231, MCF-7, Hs578t, and T47D) and one immortalized, non-tumorigenic mammary epithelial cell line (MCF-10A) were used for in vitro combination studies with BENSpm and cytotoxic drugs. Xenograft mice models generated with MDA-MB-231 cells were used for in vivo studies with BENSpm and paclitaxel.
  
  
  CONCLUSIONS
  BENSpm exhibited synergistic inhibitory effect on cell proliferation in combination with 5-FU or paclitaxel in human breast cancer cell lines (MDA-MB-231 and MCF-7) and was either antagonistic or less effective in the non-tumorigenic MCF-10A cell line. Synergism was highest with 120 h concomitant treatment or pre-treatment with BENSpm for 24 h followed by concomitant treatment for 96 additional hours. Since the cytotoxic effects of many polyamine analogues and cytotoxic agents are believed to act, in part, through induction of the polyamine catabolic enzymes SSAT and SMO, the role of these enzymes on synergistic response was evaluated in MDA-MB-231 and MCF-7 treated with BENSpm and 5-FU or paclitaxel. Combination treatments of BENSpm with 5-FU or paclitaxel resulted in induction of SSAT mRNA and activity in both cell lines compared to either drug alone, while SMO mRNA and activity were increased only in MDA-MB-231 cells. Induction was greater with BENSpm/paclitaxel combination than BENSpm/5-FU. Further, RNAi studies demonstrated that both SSAT and SMO play a significant role in the response of MDA-MB-231 cells to treatment with BENSpm and 5-FU or paclitaxel. In MCF-7 cells, only SSAT appears to be involved in the response to these treatments. In an effort to translate combination studies from in vitro to in vivo, and to form a basis for clinical setting, the in vivo therapeutic efficacy of BENSpm alone and in combination with paclitaxel on tumor regression was evaluated in xenograft mice models generated with MDA-MB-231 cells. Intraperitoneal exposure to BENSpm or taxol singly and in combination for 4 weeks resulted in significant inhibition in tumor growth. These findings help elucidate the mechanisms involved in synergistic drug response and support combinations of polyamine analogues with chemotherapeutic agents which could potentially be used in the treatment of breast cancer.
authors.affiliation: The Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, MD 21250, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Pledgie-Tracy
authors.forename: Madhavi
authors.initials: M
authors.lastname: Billam
authors.forename: Amy
authors.initials: A
authors.lastname: Hacker
authors.forename: Michele D
authors.initials: MD
authors.lastname: Sobolewski
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Woster
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Casero
authors.forename: Nancy E
authors.initials: NE
authors.lastname: Davidson
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D015394:Molecular Structure; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000235:genetics / Q000378:metabolism*; D017239:Paclitaxel / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013096:Spermine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays; D000097667:Polyamine Oxidase; D000099228:Diamine N-Acetyltransferase
chemical_list: D000123:Acetyltransferases; D000970:Antineoplastic Agents; D005472:Fluorouracil; D000587:Oxidoreductases Acting on CH-NH Group Donors; D017239:Paclitaxel; D013096:Spermine; D000097667:Polyamine Oxidase; D000099228:Diamine N-Acetyltransferase; C059685:N(1),N(11)-diethylnorspermine