title: Preferential killing of breast tumor initiating cells by N,N-diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine/tesmilifene.
abstract: OBJECTIVE
  N,N-Diethyl-2-[4-(phenylmethyl)phenoxy]ethanamine (DPPE; tesmilifene) is thought to potentiate the antineoplastic effect of cytotoxic drugs. In a phase III randomized trial for metastatic breast cancer using doxorubicin with or without DPPE, addition of the latter resulted in a significant improvement in overall survival and a trend toward a difference in progression-free survival but, paradoxically, no difference in objective tumor response. Here we tested the hypothesis that DPPE targets breast tumor-initiating cells (TICs).
  
  
  METHODS
  Human breast TICs from pleural effusions were identified as CD44(+):CD24(-/low) cells by flow cytometry and functionally by their ability to form nonadherent spheres in culture. Mouse mammary TICs from two different models of breast cancer were identified as cells capable of initiating spheres in culture and secondary tumors following transplantation into the mammary gland of syngeneic mice.
  
  
  RESULTS
  We show that at physiologically attainable concentrations, treatment with DPPE alone reduced tumorsphere formation and viability of CD44(+):CD24(-/low) breast cancer cells. The kinetics of killing varied for the different breast tumor cells and required continuous exposure to the drug. Whereas doxorubicin killed CD44(+):CD24(-/low) and CD44(-):CD24(+) cells equally well, DPPE induced apoptosis preferentially in CD44(+):CD24(-/low) cells. Treatment of Her2/Neu(+) mammary tumor cells with DPPE in vitro efficiently killed TICs, as determined by flow cytometry and transplantation assays; DPPE further cooperated with doxorubicin to completely eradicate tumorigenic cells.
  
  
  CONCLUSIONS
  Our results show that continuous treatment with DPPE alone directly targets breast TICs, and provide rationale to test for cooperation between DPPE and known drugs with efficacy toward breast cancer subtypes.
authors.affiliation: Toronto General Research Institute-University Health Network, Ontario, Canada.
authors.forename: Tao
authors.initials: T
authors.lastname: Deng
authors.forename: Jeff C
authors.initials: JC
authors.lastname: Liu
authors.forename: Kathleen I
authors.initials: KI
authors.lastname: Pritchard
authors.forename: Andrea
authors.initials: A
authors.lastname: Eisen
authors.forename: Eldad
authors.initials: E
authors.lastname: Zacksenhaus
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D051927:CD24 Antigen / Q000378:metabolism*; D002448:Cell Adhesion / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology*; D051379:Mice; D009368:Neoplasm Transplantation; D010647:Phenyl Ethers / Q000494:pharmacology*; D016066:Pleural Effusion, Malignant / Q000473:pathology*
chemical_list: D000970:Antineoplastic Agents; D051927:CD24 Antigen; C497889:CD24 protein, human; C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D010647:Phenyl Ethers; D004317:Doxorubicin; C043062:tesmilifene