Apoptosis of B-cell chronic lymphocytic leukemia cells induced by a novel BH3 peptidomimetic.
B-cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in human adults of the Western world and no definitive cure is yet available. The disease is characterized by accumulation of clonal malignant B lymphocytes resistant to apoptosis. Strategies to hit the anti-apoptotic drift of the Bcl-2 family in B-CLL cells are being explored. A novel peptidomimetic based on the BH3 domain of the pro-apoptotic protein Bim and recently shown to exert significant apoptotic activity on acute myeloid leukemia cells, both in vitro and in vivo, was assayed on ex-vivo derived leukemic cells from untreated B-CLL patients (n = 7). We found that this peptide, named 072RB, induced apoptosis of B-CLL samples at a concentration that does not affect viability of peripheral and bone marrow derived lymphocytes from healthy donors. Apoptosis was demonstrated by activation of Bak and Bax, externalization of plasma membranes phosphadydilserines, appearance of hypodiploid events in DNA flow cytometry histograms and was accompanied by dissipation of the mitochondrial transmembrane potential. Before the onset of marked apoptotic signs a progressive decline of the relevant anti-apoptotic proteins Bcl-X(L) and Mcl-1 could be observed. The negative control peptide 072RBL94A was ineffective for B-CLL cells, supporting the sequence specificity of 072RB activity. No relationship was found between responsiveness to 072RB and Mcl-1/Bcl-X(L) basal levels or decrease magnitude, possibly because of the limited sample size of the study. Altogether, we demonstrate that 072RB induces significant apoptosis of B-CLL cells subsequent to Bcl-X(L) and Mcl-1 downregulation.
Ghiotto
Fabio
F
Department of Experimental Medicine, Section of Human Anatomy, University of Genoa, Genoa, Italy.
Fais
Franco
F
Tenca
Claudya
C
Tomati
Valeria
V
Morabito
Fortunato
F
Casciaro
Salvatore
S
Mumot
Anna
A
Zoppoli
Gabriele
G
Ciccone
Ermanno
E
Parodi
Silvio
S
Bruno
Silvia
S
D017209:Apoptosis / Q000187:drug effects*; D015415:Biomarkers / Q000032:analysis; D018929:Cell Culture Techniques; D015536:Down-Regulation; D005434:Flow Cytometry; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy / Q000378:metabolism*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010455:Peptides / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000032:analysis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis; D051020:bcl-X Protein / Q000096:biosynthesis
C533898:072RB peptide; C494772:BAK1 protein, human; C494811:BCL2L1 protein, human; D015415:Biomarkers; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D010455:Peptides; D010718:Phosphatidylserines; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein