Escherichia coli verotoxin 1 mediates apoptosis in human HCT116 colon cancer cells by inducing overexpression of the GADD family of genes and S phase arrest.
The Escherichia coli verotoxin 1 (VT1) inhibits protein synthesis, cell proliferation, and damages endothelial cell in the hemolytic uremic syndrome. VT1 can specifically bind and act on endothelial cells as well as on many tumor cells because these cells express its high affinity receptor, globotriaosylceramide. This indicates that VT1 may have both antiangiogenic and antineoplastic activities. We investigated this potential of VT1 by incubating several colon cancer cell lines with VT1 for different time periods and found that HCT116 cells were especially sensitive to VT1. A combination of morphological studies, flow cytometry, DNA laddering and annexin V staining confirmed that VT1 irreversibly arrests these cells in S phase within 24 h and prolonged incubation triggers DNA fragmentation. Concomitant to the activation of the S phase checkpoint, increased levels of mRNA and proteins of growth arrest and DNA damage-inducible gene family that include GADD34, GADD45alpha, and GADD45beta was observed. Interestingly, no significant changes in expression of key cell cycle related proteins such as cdk2, cdk4, p21, p27, and p53 was found during the S phase arrest and apoptosis. We therefore suggest that GADD proteins might play an important role in VT1 induced S phase arrest and programmed cell death in HCT116 cells.
Bhattacharjee
Rabindra N
RN
Department of Bacterial Infections, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
Park
Kwon-Sam
KS
Uematsu
Satoshi
S
Okada
Kazuhisa
K
Hoshino
Katsuaki
K
Takeda
Kiyoshi
K
Takeuchi
Osamu
O
Akira
Shizuo
S
Iida
Tetsuya
T
Honda
Takeshi
T
D000943:Antigens, Differentiation / Q000235:genetics*; D017209:Apoptosis / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000235:genetics; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000473:pathology*; D029968:Escherichia coli Proteins / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D009687:Nuclear Proteins / Q000235:genetics; D054645:Protein Phosphatase 1; D016196:S Phase; D022622:Shiga Toxin 1 / Q000494:pharmacology*; D000097642:GADD45 Proteins
D000943:Antigens, Differentiation; D018797:Cell Cycle Proteins; D029968:Escherichia coli Proteins; D009687:Nuclear Proteins; D054645:Protein Phosphatase 1; D022622:Shiga Toxin 1; C439070:GADD45A protein, human; D000097642:GADD45 Proteins; C086470:GADD45B protein, human; C087519:PPP1R15A protein, human