Highly efficient, in-vivo Fas-mediated apoptosis of B-cell lymphoma by hexameric CTLA4-FasL

J Hematol Oncol. 2014 Sep 17:7:64. doi: 10.1186/s13045-014-0064-6.

Abstract

Non-Hodgkin lymphomas (NHLs) account for 4% of all malignancies. 5-year survival rate increased to 50% with new treatment modalities, however there is need for new effective treatment for the more aggressive, relapsing forms. Recently, CTLA4-FasL, that can bind to B7 and Fas receptor (Fas), was shown to induce robust apoptosis of cell lines originating from B cell lymphomas expressing both B7 and Fas, by activating pro-apoptotic signals in parallel to abrogating anti-apoptotic ones. The present study focuses on the unique properties of CTLA4-FasL as a potent apoptosis inducer of malignant cells in-vitro and in a xenograft model. CTLA4-FasL was found to naturally form a stable homo-hexamer. CTLA4-FasL induces robust apoptosis of a large variety of malignant cells while relatively sparing non-malignant ones, being more efficient when both receptors (B7 and Fas) are expressed on target cells. Even in non-B7 expressing cells, CTLA4-FasL exhibited better apoptotic activity than its parts, alone or in combination, however, only in B7 expressing cells apoptosis occurs at low concentrations and CTLA4-FasL induces activation of apoptotic signals and reduces anti-apoptotic ones. Importantly, CTLA4-FasL efficiently inhibited the growth of human B cell lineage tumors in a xenograft model, by provoking tumor cells' apoptosis. Thus, CTLA4-FasL, a natural homo-hexamer protein, induces robust apoptosis of malignant cells, in-vitro and in-vivo. In B-cell lymphoma, its potency stems from the combination of its synergistic effect of activating the caspases while abrogating the anti-apoptotic signaling, with its unique hexameric structure, making CTLA4-FasL a promising candidate for aggressive B cell lymphomas treatment.

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Blotting, Western
  • CTLA-4 Antigen / therapeutic use*
  • Cell Line, Tumor
  • Chromatography, High Pressure Liquid
  • Cross-Linking Reagents / chemical synthesis
  • Cross-Linking Reagents / therapeutic use*
  • Enzyme-Linked Immunosorbent Assay
  • Fas Ligand Protein / therapeutic use*
  • Female
  • Flow Cytometry
  • Humans
  • Isoelectric Focusing
  • Lymphoma, B-Cell / pathology*
  • Mice
  • Mice, Nude
  • Recombinant Fusion Proteins / chemical synthesis
  • Recombinant Fusion Proteins / therapeutic use*
  • Xenograft Model Antitumor Assays
  • fas Receptor / metabolism

Substances

  • CTLA-4 Antigen
  • CTLA4 protein, human
  • Cross-Linking Reagents
  • FASLG protein, human
  • Fas Ligand Protein
  • Recombinant Fusion Proteins
  • fas Receptor