title: Targeted therapy against Bcl-2-related proteins in breast cancer cells.
abstract: BACKGROUND
  Bcl-2 and Bcl-xL confer resistance to apoptosis, thereby reducing the effectiveness of chemotherapy. We examined the relationship between the expression of Bcl-2 and Bcl-xL and chemosensitivity of breast cancer cells, with the aim of developing specific targeted therapy.
  
  
  METHODS
  Four human breast cancer cell lines were examined, and the effects of antisense (AS) Bcl-2 and AS Bcl-xL phosphorothioate oligodeoxynucleotides (ODNs) on chemosensitivity were tested in vitro and in vivo. Chemosensitivity was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay, and the antitumor effect was assessed in vivo by the success of xenograft transplantation into athymic mice.
  
  
  RESULTS
  Treatment with AS Bcl-2 and Bcl-xL ODNs resulted in a sequence-specific decrease in protein expression, compared with controls. Treatment of BT-474, ZR-75-1, and MDA-MB-231 cells with AS Bcl-2 increased chemosensitivity to doxorubicin (DOX), mitomycin C (MMC), paclitaxel (TXL), and docetaxel (TXT). Transfection of the Bcl-2 gene into MDA-MB-453 cells decreased sensitivity to DOX and MMC. Treatment of MDA-MB-231, BT-474, and ZR-75-1 cells with AS Bcl-xL increased chemosensitivity to DOX, MMC and taxanes to a smaller extent than AS Bcl-2. This occurred in the setting of increased Bax and cleaved poly(ADP-ribose) polymerase, as well as decreased Bcl-2 and pAkt. AS Bcl-2 ODNs induced splenomegaly in association with increased serum IL-12, which was attenuated by methylation of the CpG motifs of AS Bcl-2; however, methylated CpG failed to negate the increased antitumor effect of AS Bcl-2. Bcl-2 and Bcl-xL, to a smaller extent, are major determinants of chemosensitivity in breast cancer cells.
  
  
  CONCLUSIONS
  Targeted therapy against Bcl-2 protein with the use of AS ODNs might enhance the effects of chemotherapy in patients with breast cancer.
authors.affiliation: Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Emi
authors.forename: Ryungsa
authors.initials: R
authors.lastname: Kim
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Tanabe
authors.forename: Yoko
authors.initials: Y
authors.lastname: Uchida
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Toge
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D005260:Female; D019254:Genes, bcl-2; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D016376:Oligonucleotides, Antisense / Q000627:therapeutic use*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis* / Q000235:genetics; D013778:Tetrazolium Salts; D013844:Thiazoles; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000970:Antineoplastic Agents; D016376:Oligonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D013778:Tetrazolium Salts; D013844:Thiazoles; D051020:bcl-X Protein; C022616:thiazolyl blue