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In vitro cytotoxic effect of proteasome inhibitor bortezomib in combination with purine nucleoside analogues on chronic lymphocytic leukaemia cells
Author(s) -
Duechler Markus,
Linke Anna,
Cebula Barbara,
Shehata Medhat,
Schwarzmeier Josef D.,
Robak Tadeusz,
Smolewski Piotr
Publication year - 2005
Publication title -
european journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 84
eISSN - 1600-0609
pISSN - 0902-4441
DOI - 10.1111/j.1600-0609.2004.00406.x
Subject(s) - bortezomib , proteasome inhibitor , xiap , propidium iodide , apoptosis , cytotoxic t cell , chronic lymphocytic leukemia , chemistry , annexin , cytotoxicity , pharmacology , cancer research , biology , immunology , in vitro , leukemia , programmed cell death , biochemistry , multiple myeloma , caspase
Objective : The anti‐tumour in vitro activity of proteasome inhibitor bortezomib (PS‐341, VELCADE) in combination with purine nucleoside analogues, cladribine (2‐CdA) and fludarabine (FA) was tested in lymphocytes derived from 26 patients with B‐cell chronic lymphocytic leukaemia (B‐CLL). Methods : Cell viability was assessed by propidium iodide staining, and apoptosis by annexin‐V and caspase activation flow cytometry assays. Additionally, expression of the apoptosis‐regulating proteins Bax, Bak, Bid, Bcl‐w, Bcl‐2, XIAP and Mcl‐1 was evaluated in B‐CLL lymphocytes. Results : Bortezomib alone induced significant, dose‐dependent cytotoxicity starting from the low concentration 2.5 n m , inducing apoptosis of B‐CLL cells. Combination of this agent with 2‐CdA or FA resulted in an increase of cytotoxicity when compared with that mediated by single drugs. The observed increase was especially evident when 5 n m of bortezomib were combined with suboptimal doses of 2‐CdA or FA. The combination index (CI) was 0.87 for bortezomib + 2‐CdA and 0.82 for bortezomib + FA, indicating an evident additive effect of these combinations. Moreover, B‐CLL cells were more sensitive to proteasome inhibitor used alone or combined with 2‐CdA or FA comparing to CD3+ lymphocytes. Corresponding to enhanced apoptosis, the expression levels of several apoptosis‐regulating proteins were altered. The most pronounced changes were down‐regulation of XIAP and up‐regulation of Bid proteins by the combination of bortezomib with either 2‐CdA or FA. Conclusions : This study suggest that the in vitro cytotoxic effect through proteasome inhibition by bortezomib can be increased substantially with low doses of the purine nucleoside analogues, 2‐CdA and FA, and that this effect on B‐CLL cell is selectively higher than on normal, CD3‐positive lymphocytes.