Additive effect of Apo2L/TRAIL and Adeno-p53 in the induction of apoptosis in myeloma cell lines.
OBJECTIVE
We have previously shown that Adenovirus-p53 (Ad-p53) is a potent inducer of apoptosis in myeloma cells expressing nonfunctional p53 and low levels of bcl-2 and that Apo2L/TRAIL is a potent inducer of apoptosis, independent of bcl-2. A study was designed to test the synergy between Ad-p53 and Apo2L/TRAIL in the induction of apoptosis in relation to the expression of DR4/DR5 and DcR1, in cells undergoing Ad-p53-induced apoptosis.


METHODS
Replication deficient Ad-p53 and human recombinant Apo2L/TRAIL were used. Myeloma cells with mutated/w.t. p53 and varying expression of bcl-2 were used to test the effect of Ad-p53, Apo2L/TRAIL, or both, on apoptosis, measured by annexin V.


RESULTS
Treatment with Ad-p53 resulted in a dose-dependent apoptosis concomitant with a dose-dependent increase in the expression of DR4/DR5 and a decrease in the expression of DcR1, in Ad-p53-sensitive cell lines. In these cells, addition of Apo2L/TRAIL to cells treated with Ad-p53 resulted in a dose-dependent increase in apoptosis. Myeloma cells resistant to Ad-p53 had high levels of DR4/DR5 and high levels of DcR1 and treatment with Ad-p53 did not reduce the expression of DcR1. Also, addition of Apo2L/TRAIL to Ad-p53 did not affect the level of apoptosis beyond the level of apoptosis observed with Apo2L/TRAIL alone.


CONCLUSIONS
1) Cotreatment with Ad-p53 and Apo2L/TRAIL resulted in additive apoptosis in myeloma cells expressing nonfunctional p53 and low levels of bcl-2. 2) Resistance to Ad-p53 or to the combination of Ad-p53 and Apo2L/TRAIL was not due to the lack of adenovirus receptor (CAR) or low expression of DR4/DR5 but rather due to the relatively high expression of DcR1 receptor.
Liu
Q
Q
University of Texas Health Science Center, San Antonio, Tex., USA.
El-Deiry
W S
WS
Gazitt
Y
Y
D000256:Adenoviridae; D017304:Annexin A5 / Q000032:analysis; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D019254:Genes, bcl-2; D016158:Genes, p53; D015804:HLA-DR4 Antigen / Q000032:analysis / Q000235:genetics; D015805:HLA-DR5 Antigen / Q000032:analysis / Q000235:genetics; D006801:Humans; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D009101:Multiple Myeloma / Q000473:pathology*; D016296:Mutagenesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D011994:Recombinant Proteins / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection / Q000379:methods; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D017304:Annexin A5; D051017:Apoptosis Regulatory Proteins; D015804:HLA-DR4 Antigen; D015805:HLA-DR5 Antigen; D008562:Membrane Glycoproteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53