CD47 agonist peptides induce programmed cell death in refractory chronic lymphocytic leukemia B cells via PLCγ1 activation: evidence from mice and humans

PLoS Med. 2015 Mar 3;12(3):e1001796. doi: 10.1371/journal.pmed.1001796. eCollection 2015 Mar.


Background: Chronic lymphocytic leukemia (CLL), the most common adulthood leukemia, is characterized by the accumulation of abnormal CD5+ B lymphocytes, which results in a progressive failure of the immune system. Despite intense research efforts, drug resistance remains a major cause of treatment failure in CLL, particularly in patients with dysfunctional TP53. The objective of our work was to identify potential approaches that might overcome CLL drug refractoriness by examining the pro-apoptotic potential of targeting the cell surface receptor CD47 with serum-stable agonist peptides.

Methods and findings: In peripheral blood samples collected from 80 patients with CLL with positive and adverse prognostic features, we performed in vitro genetic and molecular analyses that demonstrate that the targeting of CD47 with peptides derived from the C-terminal domain of thrombospondin-1 efficiently kills the malignant CLL B cells, including those from high-risk individuals with a dysfunctional TP53 gene, while sparing the normal T and B lymphocytes from the CLL patients. Further studies reveal that the differential response of normal B lymphocytes, collected from 20 healthy donors, and leukemic B cells to CD47 peptide targeting results from the sustained activation in CLL B cells of phospholipase C gamma-1 (PLCγ1), a protein that is significantly over-expressed in CLL. Once phosphorylated at tyrosine 783, PLCγ1 enables a Ca2+-mediated, caspase-independent programmed cell death (PCD) pathway that is not down-modulated by the lymphocyte microenvironment. Accordingly, down-regulation of PLCγ1 or pharmacological inhibition of PLCγ1 phosphorylation abolishes CD47-mediated killing. Additionally, in a CLL-xenograft model developed in NOD/scid gamma mice, we demonstrate that the injection of CD47 agonist peptides reduces tumor burden without inducing anemia or toxicity in blood, liver, or kidney. The limitations of our study are mainly linked to the affinity of the peptides targeting CD47, which might be improved to reach the standard requirements in drug development, and the lack of a CLL animal model that fully mimics the human disease.

Conclusions: Our work provides substantial progress in (i) the development of serum-stable CD47 agonist peptides that are highly effective at inducing PCD in CLL, (ii) the understanding of the molecular events regulating a novel PCD pathway that overcomes CLL apoptotic avoidance, (iii) the identification of PLCγ1 as an over-expressed protein in CLL B cells, and (iv) the description of a novel peptide-based strategy against CLL.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Animals
  • Apoptosis / drug effects*
  • B-Lymphocytes / metabolism*
  • CD47 Antigen / metabolism*
  • Drug Resistance, Neoplasm*
  • Female
  • Humans
  • Leukemia, Lymphocytic, Chronic, B-Cell / blood
  • Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy
  • Leukemia, Lymphocytic, Chronic, B-Cell / metabolism*
  • Male
  • Mice
  • Mice, Inbred NOD
  • Middle Aged
  • Peptides / pharmacology*
  • Peptides / therapeutic use
  • Phospholipase C gamma / metabolism*
  • Thrombospondin 1 / therapeutic use


  • CD47 Antigen
  • Peptides
  • Thrombospondin 1
  • Phospholipase C gamma

Grants and funding

This work was supported by Association Laurette Fugain (ALF 2011/02), Fondation de France-Comité Cancer (2012-00034116), Ligue Contre le Cancer-Comité de Paris (RS15/75–63), Inserm Transfert, French National Cancer Institute (INCa-5839), and French National Research Agency (ANR-12-EMMA-0045; ANR-Genopath “Target Channel”). ACMT received PhD fellowships from CONACYT (Mexico) and Fondation ARC. CQ holds a postdoctoral support from Fondation pour la Recherche Medicale. HB received a PhD fellowship from the French Research Ministry. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.