title: 5-Fluorouracil enhances apoptosis sensitivity of T lymphocytes mediated by CD3 epsilon.
abstract: Previous studies by our laboratory have reported that the T cell receptor (TCR) TCR/CD3 complex could mediate activation as well as apoptosis of T lymphocytes. Two tyrosine residues in the ITAM (immuno-receptor tyrosine-based activation motifs) of CD3 epsilon were required for apoptosis signalling of Jurkat T lymphocytes. Stable cell lines TJK and T3JK produced from CD8(-) Jurkat T lymphocytes by transfection with wild-type and mutant CD8 epsilon (fusion of the extracellular and transmembrane domains of human CD8 alpha to the intracellular domain of mouse CD3 epsilon), were used with CD8(-) Jurkat T lymphocytes for studying the role of single intact CD3 epsilon. 5-Fluorouracil (5-FU), a chemotherapeutic drug can induce cell death of many tumour cell lines. In the present experiments, we examined the expression of caspase-3, p53 and Bid in the three cell lines induced by 5-FU and/or anti-CD8 antibody. We found high expression of p53 during activation-induced cell death of TJK cells mediated by anti-CD8 antibody and apoptosis of TJK and T3JK induced by 5-FU, implicating p53 involvement in apoptosis of leukemia cells induced by anti-CD8 antibody and 5-FU. We also detected the active form of caspase-3 and Bid in apoptotic leukemia cells after treatment with 5-FU and/or anti-CD8 antibody, indicating that the drug and antibody induced cell death through caspase-3 and the signal pathway may involve the Bcl-2 protein family. Our results showed that combined treatment with 5-FU and anti-CD8 antibody could enhance the rate of apoptosis induced by 5-FU or anti-CD8 antibody through increased expression of p53 and by promoting activation of caspase-3 and Bid. This suggests that the combination of 5-FU and anti-CD8 antibody may play an important role in inducing apoptosis of leukemia cells.
authors.affiliation: National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Cheng
authors.forename: Yanxin
authors.initials: Y
authors.lastname: Liu
authors.forename: Shilian
authors.initials: S
authors.lastname: Liu
authors.forename: Dexian
authors.initials: D
authors.lastname: Zheng
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D017209:Apoptosis / Q000276:immunology*; D051023:BH3 Interacting Domain Death Agonist Protein; D017252:CD3 Complex / Q000235:genetics / Q000276:immunology*; D016827:CD8 Antigens / Q000235:genetics / Q000276:immunology; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D005434:Flow Cytometry; D005472:Fluorouracil / Q000494:pharmacology*; D049452:Green Fluorescent Proteins / Q000032:analysis; D006801:Humans; D019169:Jurkat Cells; D015458:Leukemia, T-Cell / Q000188:drug therapy / Q000276:immunology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology*; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; D017252:CD3 Complex; D016827:CD8 Antigens; D002352:Carrier Proteins; C485468:Cd3e protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D005472:Fluorouracil