title: Involvement of Tiam1 in apoptosis induced by bufalin in HeLa cells.
abstract: BACKGROUND
  It has been previously demonstrated that bufalin, an active agent in the Chinese medicine chan'su, induces apoptosis in human leukemia cells by altering the expression of apoptosis-related genes, such as bcl-2 and c-myc. Tiam1 was also found to play a critical role in bufalin-induced apoptosis through the activation of the Rac1, PAK and JNK pathway in human leukemia cell lines. In the present study, the involvement of the Tiam1 gene products in bufalin-induced apoptosis in human solid tumor HeLa cells was examined.
  
  
  METHODS
  HeLa cells were treated with 10(-8) M bufalin and apoptosis was measured by ELISA quantification of nucleosomes. Tiam1 mRNA levels were quantified by real-time PCR analysis and inhibited by transfected siRNA specific for Tiam1.
  
  
  RESULTS
  Apoptosis was induced in HeLa cells by treatment with 10(-8) M bufalin. Expression of both Tiam1 mRNA and its protein was induced 0.5 h after the start of the bufalin treatment. Transfection of Tiam1-specific siRNA into HeLa cells markedly inhibited bufalin-induced apoptosis.
  
  
  CONCLUSIONS
  Our results suggest that Tiam1 is a downstream mediator of bufalin-induced apoptosis in the human solid tumor HeLa cell line, as well as in leukemia cell lines.
authors.affiliation: Laboratory of Biological Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo 142-8555, Japan.
authors.lastname: Cao-Hong
authors.forename: Toshiko
authors.initials: T
authors.lastname: Shibayama-Imazu
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Masuda
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Shinki
authors.forename: Shigeo
authors.initials: S
authors.lastname: Nakajo
authors.forename: Kazuyasu
authors.initials: K
authors.lastname: Nakaya
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002018:Bufanolides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D002018:Bufanolides; D020662:Guanine Nucleotide Exchange Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000075684:T-Lymphoma Invasion and Metastasis-inducing Protein 1; C087334:TIAM1 protein, human; C022777:bufalin