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6th ESACP Congress, Heidelberg, April 7-11, 1999 |
A027
Apoptosis is a genetically regulated cell death process which results
in a variety of morphological changes like chromatin condensation and
DNA fragmentation. We have examined cytosolic pH, mitochondrial membrane
potential and reactive oxygen species (ROS) during daunorubicin (DNR)
induced apoptosis in human leukemic HL60 cells. We showed that in sensitive
cells apoptosis was accompanied by significant acidification of the cytosol
and an increase of ROS level without mitochondrial membrane depolarization.
The response to an apoptotic stimulus is determined and regulated in part
by mitochondrial oncoproteins which include proteins of the bcl-2 family
(bcl-2, bax, bcl-xL). Thus, we investigated the effect of these proteins
on the induction of this phenomenon in the multidrug-resistant HL60 cells
established with vincristine (HL60/VCR), DNR (HL60/DNR), C2-ceramide
(HL60/C2), lonidamine (HL60/L2) and VP16 (HL60/V2) respectively. We showed
that sensitive and HL60/VCR cells were able to undergo apoptosis when
treated with DNR, while the other resistant cell lines do not. Western
blotting analysis shows that bax is expressed at the same level in all
cell lines whereas bcl-2 is overexpressed only in HL60/VCR. However, the
other resistant cell lines displayed a higher expression of bclxL at the
expense of the bcl-2 expression. Interestingly, bcr-abl, a dysregulated
tyrosine kinase, was detected in cell lines overexpressing bcl-xL.
Treatment with 1ÁM of the tyrosine kinase inhibitor CGP57148B commit
these resistant cells to undergo apoptosis. Inhibition of the bcr-abl
was accompanied by a decrease of bcl-xL expression. These data suggest
that in addition of the multidrug-resistance phenotype, bcr-abl translocation
and bclxL overexpression could also account for the development of resistance
to cell death induced by anthracyclines in leukemic cells and that the
CGP57148B could be useful for reversal of this phenotype.
CGP57148B AN INHIBITOR OF THE BCR-ABL TYROSINE KINASE COMMITS RESISTANT
HL60 CELLS TO UNDERGO APOPTOSIS THROUGH BCL-XL DOWN-REGULATION
Belhoussine R 1, Morjani H 1, Palissot T 1, Belloc F 2,
Dufer J 1, Manfait M 1
1 Unité Médian, UFR de Pharmacie, Université de Reims, Reims Cedex,
France
2 Laboratoire d'Hématologie, Hôpital Haut Lêvèque, Pessac, France