Involvement of Tiam1 in apoptosis induced by bufalin in HeLa cells.
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.
Cao-Hong
Laboratory of Biological Chemistry, School of Pharmaceutical Sciences, Showa University, Tokyo 142-8555, Japan.
Shibayama-Imazu
Toshiko
T
Masuda
Yutaka
Y
Shinki
Toshimasa
T
Nakajo
Shigeo
S
Nakaya
Kazuyasu
K
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
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