[Mechanisms of sensitization by 8-chloro-adenosine of human tumor cells to TRAIL-induced apoptosis].
OBJECTIVE
To study the effect of 8-chloro-adenosine (8-Cl-Ado) on the sensitivity of human hepatoma and breast cancer cell lines to TRAIL-induced apoptosis in vitro and its mechanisms.


METHODS
Recombinant soluble TRAIL (rsTRAIL) or 8-Cl-Ado was used to treat hepatoma cell line BEL-7402 and breast cancer cell line MCF-7 in vitro. MTT assay was used to evaluate cell viability. The effect of cotreatment with rsTRAIL and 8-Cl-Ado was analyzed. NF-kappaB activity reporter plasmid was designed to measure the activity of transcription factor NF-kappaB. After transient transfection with the reporter plasmid, which contains NF-kappaB-responsive elements, into the cell lines, cells were treated with rsTRAIL and/or 8-Cl-Ado, then the activity of the reporter gene luciferase was determined. Different kinds of caspase inhibitors were used to measure the effect of caspases in the rsTRAIL and/or 8-Cl-Ado induced apoptosis.


RESULTS
8-Cl-Ado could greatly enhance sensitivity of BEL-7402 and MCF-7 cells to reTRAIL. Treatment with 8-Cl-Ado and rsTRAIL inactivated transcription factor NF-kappaB and induced apoptosis in BEL-7402, but not in MCF-7. Caspase family inhibitor could not prevent apoptosis induced by 8-Cl-Ado and rsTRAIL in BEL-7402 cells, however, it could block apoptosis in MCF-7 cells, indicating that two different apoptosis pathways in MCF-7 and BEL-7402 might exist, one was caspase dependent and the other caspase independent. Moreover, all of the inhibitors of caspse-3, -8 and -9 could not block apoptosis induced by the co-treatment.


CONCLUSIONS
8-chloro-adenosine can enhance the sensitivity of human hepatoma cell line BEL-7402 and breast cancer cell line MCF-7 to rsTRAIL, even though MCF-7 is TRAIL-resistant. 8-Cl-Ado combined with rsTRAIL can trigger different signal pathways in MCF-7 and BEL-7402, which are caspase dependent and independent, respectively.
Wang
Ming-Jie
MJ
National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100005, China.
Liu
Yan-Xin
YX
Zhang
Jin-Chun
JC
Liu
Shi-Lian
SL
Zheng
De-Xian
DX
D015762:2-Chloroadenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D045744:Cell Line, Tumor; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D051017:Apoptosis Regulatory Proteins; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D015762:2-Chloroadenosine; C075440:8-chloroadenosine