HSP90 inhibition results in apoptosis of Philadelphia acute lymphoblastic leukaemia cells: an attractive prospect of new targeted agents.
OBJECTIVE
HSP90 targeting is a promising therapeutic approach in cancer. 17-AAG is an HSP90 inhibitor with completed Phase I trials in patients with advanced cancer and recently published Phase II trials. The aim of this work was to study the expression of HSP 90 and apoptotic proteins, the effects in culture of 17-AAG on cell survival and apoptosis and to compare Philadelphia-positive (Ph+) ALL to common B cell ALL, in ALL cell lines and in patients' cells collected at ALL diagnosis.


METHODS
We analysed 2 ALL cell lines and 63 leukaemic samples from patients treated in our institution (44 common B cell ALL and 19 Ph+ ALL). We performed flow cytometry analysis of bone marrow aspiration and cell lines with a combination of anti-HSP90, Bax, Bcl-2 and Bcl-xl antibodies. Apoptosis after cell culture (in presence or not of 17-AAG) was assessed using Annexin V and activated caspase-3 staining.


RESULTS
Ph+ ALL cells appeared to be more sensitive to 17-AAG cytotoxicity with a 100 % mortality rate after exposure to 10 μM for 24 h (vs. 62 % for B-common ALL). A high percentage of HSP90-positive cells (in Ph+ ALL samples) was associated with high sensitivity to 17-AAG. 17-AAG induced apoptosis in a dose-dependent manner and was associated with down-regulation of Bcl-2 and Bcl-Xl expression and up-regulation of Bax expression.


CONCLUSIONS
Considering that Bcr-Abl constitutes HSP 90 substrates, HSP 90 inhibition could be of particular interest for Ph+ ALL disease, even in patients harbouring resistance to tyrosine kinase inhibitor therapy.
Département d'Hématologie, Institut de Cancérologie Lucien Neuwirth, 108 bis avenue Albert Raimond, 42270 Saint Priest en Jarez, France. emmanuelle.tavernier@icloire.fr
Emmanuelle
E
Tavernier
Pascale
P
Flandrin-Gresta
Françoise
F
Solly
Lauren
L
Rigollet
Jérôme
J
Cornillon
Karine
K
Augeul-Meunier
Jean-Louis
JL
Stephan
Aurélie
A
Montmartin
Annie
A
Viallet
Denis
D
Guyotat
Lydia
L
Campos
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D016227:Benzoquinones / Q000494:pharmacology*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002648:Child; D002675:Child, Preschool; D005434:Flow Cytometry; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007223:Infant; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D008875:Middle Aged; D058990:Molecular Targeted Therapy / Q000379:methods; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D055815:Young Adult; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism
C494826:BAX protein, human; C494811:BCL2L1 protein, human; D016227:Benzoquinones; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C112765:tanespimycin; D053148:Caspase 3