Flavopiridol induces apoptosis in B-cell chronic lymphocytic leukaemia cells through a p38 and ERK MAP kinase-dependent mechanism.
Flavopiridol, a synthetic flavone, has been previously shown to induce apoptosis in B-cell chronic lymphocytic leukaemia (B-CLL) cells in vitro. The apoptosis was associated with a concomitant activation of caspase-3 without evidence of dependence on functional p53 or Bcl-2 family modulation. In this study, we examined flavopiridol-induced apoptosis in terms of upstream caspase activity, cell cycle distribution and signal transduction, in order to elucidate the mechanism of action of this potent cytotoxic agent. Flavopiridol-induced apoptosis was significantly abrogated by the caspase-9 inhibitor Z-LEHD-FMK (p = 0.002; paired t-test) but was not altered by the caspase-8 inhibitor Z-IETD-FMK (p = 0.37; paired t-test). There was a concentration-dependent increase in a sub G0/G1 peak indicative of apoptotic cells but if these cells were excluded by gating no other cell cycle perturbations were observed suggesting that flavopiridol is capable of inducing apoptosis in cells in all phases of the cell cycle. Significantly, apoptosis was associated with activation of p38 MAP kinase and suppression of ERK activity (p = 0.0036 and p = 0.0048, respectively; paired t-test). These results show for the first time that flavopiridol modulates specific cellular signal transduction pathways in B-CLL cells thereby altering the balance between survival and cell death signals and providing a rationale for the p53-independent nature of flavopiridol-induced apoptosis. Further work is required to identify whether combinations of conventional chemotherapeutic drugs and novel agents like flavopiridol can be used to improve patient outcomes in the treatment of B-CLL.
Pepper
Chris
C
Department of Haematology, Llandough Hospital, Penlan Road, Penarth, Vale of Glamorgan, CF64 2XX, UK.
Thomas
Alun
A
Fegan
Chris
C
Hoy
Terry
T
Bentley
Paul
P
D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000473:pathology*; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology*; D016192:Resting Phase, Cell Cycle; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases
D000970:Antineoplastic Agents; D005419:Flavonoids; D010880:Piperidines; C077990:alvocidib; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases