Latent sensitivity to Fas-mediated apoptosis after CD40 ligation may explain activity of CD154 gene therapy in chronic lymphocytic leukemia.

Abstract

Patients with chronic lymphocytic leukemia (CLL) treated with adenovirus (Ad)-CD154 (CD40L) gene therapy experience reductions in leukemia cell counts and lymph node size associated with induction of the death receptor Fas (CD95). CD4 T cell lines can induce apoptosis of CD40-activated CLL cells via a CD95 ligand (CD95-L)-dependent mechanism. To examine whether CD95-L was sufficient to induce cytolysis of CD40-activated CLL cells, we used Chinese hamster ovary cells transfected with CD95-L as cytotoxic effector cells. CD40-activated CLL cells were initially resistant to CD95-mediated apoptosis despite high-level expression of CD95. However, after 72 h, CLL cells from seven of seven patients became increasingly sensitive to CD95-mediated apoptosis. This sensitivity correlated with a progressive decline in Flice-inhibitory protein (FLIP), which was induced within 24 h of CD40 ligation. Down-regulation of FLIP with an antisense oligonucleotide or a pharmacologic agent, however, was not sufficient to render CLL cells sensitive to CD95-mediated apoptosis in the 24-72 h after CD40 activation. Although the levels of pro-Caspase-8 appeared sufficient, inadequate levels of Fas-associated death domain protein (FADD) and DAP3 may preclude assembly of the death-inducing signaling complex. Seventy-two hours after CD40 ligation, sensitivity to CD95 and a progressive increase in FADD and DAP3 were associated with the acquired ability of FADD and FLIP to coimmunoprecipitate with the death-inducing signaling complex after CD95 ligation. Collectively, these studies reveal that CD40 ligation on CLL B cells induces a programmed series of events in which the cells initially are protected and then sensitized to CD95-mediated apoptosis through shifts in the balance of the anti- and proapoptotic proteins FLIP and FADD.

• Authors: Peter Chu, Dieter Deforce, Irene M Pedersen, Youngsoo Kim, Shinichi Kitada, John C Reed, Thomas J Kipps
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 99 Issue 6 Pg. 3854-9 (Mar 19 2002) ISSN: 0027-8424 [Print] United States
• PMID: 11891278 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid
• CASP8 and FADD-Like Apoptosis Regulating Protein
• CD40 Antigens
• CFLAR protein, human
• Carrier Proteins
• FASLG protein, human
• Fas Ligand Protein
• Intracellular Signaling Peptides and Proteins
• Membrane Glycoproteins
• fas Receptor
• CD40 Ligand
• Oleanolic Acid
• CASP8 protein, human
• CASP9 protein, human
• Caspase 8
• Caspase 9
• Caspases

Topics

• Animals
• Apoptosis
• CASP8 and FADD-Like Apoptosis Regulating Protein
• CD4-Positive T-Lymphocytes (immunology, metabolism)
• CD40 Antigens (metabolism)
• CD40 Ligand (administration & dosage, genetics, metabolism, therapeutic use)
• CHO Cells
• Carrier Proteins (genetics, metabolism)
• Caspase 8
• Caspase 9
• Caspases (metabolism)
• Cricetinae
• Down-Regulation (drug effects)
• Fas Ligand Protein
• Gene Expression Regulation, Neoplastic (drug effects)
• Genetic Therapy
• Humans
• Intracellular Signaling Peptides and Proteins
• Leukemia, Lymphocytic, Chronic, B-Cell (genetics, metabolism, pathology, therapy)
• Membrane Glycoproteins (genetics, metabolism)
• Oleanolic Acid (analogs & derivatives, pharmacology)
• Precipitin Tests
• Signal Transduction
• Time Factors
• Tumor Cells, Cultured
• fas Receptor (metabolism)