Inhibition of TRAIL-induced apoptosis by IL-8 is mediated by the p38-MAPK pathway in OVCAR3 cells.
BACKGROUND
TRAIL (TNF-Related Apoptosis Inducing Ligand) is a member of the TNF superfamily of cell death inducing ligands. Interestingly, while malignant cells are responsive to TRAIL-induced cell death when used alone or in combination with other agents, normal cells do not appear to be sensitive to this ligand, making it a desirable therapeutic compound against many cancers, including many ovarian carcinomas. Interleukin-8 (IL-8), a member of the C-X-C chemokine family, has been found to be at significantly higher level in the ascites from patients with ovarian cancer. We have previously demonstrated a role for IL-8 in blocking TRAIL's ability to induce apoptosis in the ovarian cancer cell line, OVCAR3, possibly by repressing the DR4 TRAIL receptor expression and blocking caspase-8 cleavage. In addition, we showed a member of the mitogen-activated protein kinase (MAPK) superfamily, p38gamma, is among the genes regulated in OVCAR3 cells by TRAIL and IL-8. The present study further investigates involvement of the p38 MAPK pathway in IL-8's ability to block TRAIL-induced apoptosis in the ovarian surface epithelial cancer cell line, OVCAR3.


RESULTS
In this study we demonstrate that p38gamma as well as p38alpha play a significant role in IL-8's ability to block TRAIL-induced apoptosis. Through array analysis, as well as confirmation with other methods, we detected regulation of p38gamma and p38alpha following treatment of the cancer cell line with IL-8 or TRAIL. We also tested two other isoforms of p38 MAPK, p38beta and p38delta, but did not find significant regulation by IL-8 or TRAIL. We also examined activation of the p38 MAPK pathway, up-stream as well as down-stream, and noticed activation of the pathway following treatment with TRAIL and decreased activity when IL-8 was introduced. With the use of specific inhibitors, we were able to further confirm the role of this pathway in TRAIL-induced apoptosis, and IL-8's ability to block this apoptosis, in ovarian cancer cell lines.


CONCLUSIONS
Taken together, these results further solidify the role of IL-8 in blocking the TRAIL-induced apoptosis in these ovarian carcinoma cells and provide new molecular insight into this potentially important therapeutic target.
Abdollahi
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T
Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19106, USA. tabdolahi@hotmail.com
Robertson
N M
NM
Abdollahi
A
A
Litwack
G
G
D051698:Activating Transcription Factor 2 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D016209:Interleukin-8 / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D048371:MAP Kinase Kinase 3 / Q000378:metabolism; D048669:MAP Kinase Kinase 6 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D013997:Time Factors; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D007093:Imidazoles; D016209:Interleukin-8; D007527:Isoenzymes; D011725:Pyridines; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; C482530:MAP2K3 protein, human; C482566:MAP2K6 protein, human; C093642:SB 203580