Isolation and characterization of an apoptosis-resistant variant of human leukemia HL-60 cells that has switched expression from Bcl-2 to Bcl-xL.
Human promyelocytic leukemia HL-60 cells treated with 8-chloroadenosine-3',5'-cyclic monophosphate (8-Cl-cAMP) undergo growth arrest and subsequently die by apoptosis. We describe here the isolation of a variant of HL-60 cells, HCW-2, which was resistant to the cytotoxic effects of 8-Cl-cAMP, but still underwent growth arrest. Thus, HCW-2 cells appeared to be altered in their ability to undergo apoptosis. HCW-2 cells were also completely refractory to the apoptotic action of cycloheximide and staurosporine, two compounds which were very potent inducers of apoptosis in the parental HL-60 cells, suggesting that the resistance to apoptosis was not unique to 8-Cl-cAMP. Western blot analysis demonstrated that the parental HL-60 cells expressed both Bcl-2 and Bax, two factors known to be intimately involved in the control of apoptosis. Surprisingly, HCW-2 cells no longer expressed Bcl-2 protein and paradoxically contained Bax protein at a level that was approximately 50-fold higher than in HL-60 cells. However, Northern and Western analyses indicated that the apoptotic suppressor gene, bcl-xL, which is not expressed in the parental HL-60 cells, was expressed in HCW-2 cells. Thus, the Bcl-2-independent resistance of HCW-2 cells to apoptotic induction is discussed in terms of the expression of bcl-xL.
Han
Z
Z
Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA.
Chatterjee
D
D
Early
J
J
Pantazis
P
P
Hendrickson
E A
EA
Wyche
J H
JH
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology; D017209:Apoptosis; D001483:Base Sequence; D003513:Cycloheximide / Q000494:pharmacology; D018922:HL-60 Cells / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D019253:Proto-Oncogene Proteins c-bcl-2; D019311:Staurosporine; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D000470:Alkaloids; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003513:Cycloheximide; C044258:8-chloro-cyclic adenosine monophosphate; D019311:Staurosporine