Transforming growth factor-beta-mediated apoptosis in the Ramos B-lymphoma cell line is accompanied by caspase activation and Bcl-XL downregulation

Exp Cell Res. 1998 Jul 10;242(1):244-54. doi: 10.1006/excr.1998.4096.


Upon transforming growth factor-beta (TGF-beta) treatment, Ramos cells, a B-cell lymphoma cell line, undergo apoptosis, as measured by annexin V labeling, DNA fragmentation, and propidium iodide staining. Apoptosis could be observed by 24 h after TGF-beta exposure and occurred before the development of a significant blockage of cell cycle progression. TGF-beta-mediated apoptosis was also accompanied by a strong induction of caspase-3 subfamily activity. Incubation of cells with the caspase inhibitor Z-VAD.FMK at 20 microM, but not at 10 microM, prevented TGF-beta-induced apoptosis from occurring. By comparison, caspase-3 subfamily activity was 87% inhibited at 10 microM Z-VAD.FMK and completely inhibited at 20 microM. Because of TGF-beta's well-established role of regulating gene transcription, the mRNA levels for proteins associated with apoptosis (Fas- and Fas-associated proteins, Bcl-2 family members, IAP proteins, and I kappa B) were also studied. After 24 h of TGF-beta treatment, the most significant mRNA changes occurred with Bcl-XL (two-fold decrease) and Bik (twofold increase). TGF-beta treatment also resulted after 48 h in a fivefold decrease in Bcl-XL protein levels, based on immunoblotting analysis. Therefore, TGF-beta-mediated apoptosis involves the activation of caspases. In addition, TGF-beta transcriptionally regulates Bcl-2 family members, Bcl-XL and Bik, to further influence the apoptosis process.

MeSH terms

  • Amino Acid Chloromethyl Ketones / pharmacology
  • Annexin A5 / metabolism
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins
  • B-Lymphocytes / cytology*
  • B-Lymphocytes / enzymology
  • Burkitt Lymphoma
  • Caspase 3
  • Caspases*
  • Cell Cycle
  • Cysteine Endopeptidases / metabolism*
  • Cysteine Proteinase Inhibitors / pharmacology
  • DNA / analysis
  • Enzyme Activation
  • Gene Expression Regulation, Neoplastic
  • Humans
  • I-kappa B Proteins
  • Membrane Proteins*
  • Mitochondrial Proteins
  • Proteins / genetics
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins c-bcl-2 / analysis
  • Proto-Oncogene Proteins c-bcl-2 / genetics*
  • RNA, Messenger / analysis
  • Transforming Growth Factor beta / pharmacology*
  • Tumor Cells, Cultured
  • X-Linked Inhibitor of Apoptosis Protein
  • bcl-X Protein
  • fas Receptor / genetics


  • Amino Acid Chloromethyl Ketones
  • Annexin A5
  • Apoptosis Regulatory Proteins
  • BCL2L1 protein, human
  • BIK protein, human
  • Cysteine Proteinase Inhibitors
  • I-kappa B Proteins
  • Membrane Proteins
  • Mitochondrial Proteins
  • Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • Transforming Growth Factor beta
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • bcl-X Protein
  • benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
  • fas Receptor
  • DNA
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • Cysteine Endopeptidases