Influence of Bcl-2 overexpression on the ceramide pathway in daunorubicin-induced apoptosis of leukemic cells.
We have previously demonstrated that daunorubicin (DNR) induces apoptosis in some leukemic myeloid cell lines. We investigated a potential protective role for Bcl-2 in apoptosis induced by DNR in two leukemic cell lines, one myeloid and one lymphoid, overexpressing the anti-apoptotic gene Bcl-2. Parental cells treated with DNR exhibited classical features of apoptosis 6 h after drug exposure, all the cells being dead after 30-48 h. In contrast, overexpression of Bcl-2 significantly delayed, but did not prevent the occurrence of DNR-induced apoptosis, with no surviving cells 96 h after drug exposure. To elucidate the mechanism of the protection mediated by Bcl-2, we explored the signaling pathway which initiates DNR-induced apoptosis. In this report, we show that, in both the myeloid and lymphoid parental cell lines, DNR triggered a sphingomyelin (SM) hydrolysis after 10-15 min with a concomitant ceramide generation. Moreover, exogenous ceramide induced DNA fragmentation in these cells, with levels similar to those observed with DNR treatment. In contrast, Bcl-2 overexpression protected the cells against apoptosis induced by ceramide treatment, without preventing the early SM hydrolysis nor the ceramide generation in these cells. Our results strongly suggest that Bcl-2-mediated protection of DNR-induced apoptosis is effected downstream of the SM-ceramide signaling pathway.
Allouche
M
M
CJF INSERM 9503, Centre Claudius Regaud, Toulouse, France.
Bettaieb
A
A
Vindis
C
C
Rousse
A
A
Grignon
C
C
Laurent
G
G
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D002051:Burkitt Lymphoma / Q000378:metabolism / Q000473:pathology; D002518:Ceramides / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000378:metabolism; D003630:Daunorubicin / Q000494:pharmacology*; D018922:HL-60 Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D006868:Hydrolysis; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014161:Transduction, Genetic; D051028:bcl-2-Associated X Protein
D000903:Antibiotics, Antineoplastic; D002518:Ceramides; D004273:DNA, Neoplasm; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D003630:Daunorubicin