Hypoxia-induced activation of p38 mitogen-activated protein kinase and phosphatidylinositol 3'-kinase signaling pathways contributes to expression of interleukin 8 in human ovarian carcinoma cells.
OBJECTIVE
Overexpression of interleukin 8 (IL-8) is associated with disease progression in human ovarian cancer. Hypoxia, a common feature in solid tumors, induces IL-8 expression in human ovarian carcinoma cells through activation of nuclear factor-kappa B and activating protein-1. Here we show the upstream components of these signal transduction pathways that lead to IL-8 expression under hypoxia.


METHODS
We incubated Hey-A8 human ovarian carcinoma cells under hypoxic condition (1% O(2)) and determined hypoxia regulation of phosphatidylinositol 3'-kinase (PI3K)/Akt pathway, mitogen-activated protein kinases (MAPKs), and effects of ras and vascular endothelial growth factor by Western and Northern blots, the use of specific inhibitors, in vitro kinase assays, luciferase reporter genes, and ELISA.


RESULTS
While investigating the upstream signaling pathways, we found that Akt kinase and p38 MAPK are activated by hypoxia. Both hypoxia-induced Akt and p38 MAPK functional activity, and IL-8 mRNA and protein expression were reduced with the inhibition of PI3K and p38 MAPK. Oncogenic ras overexpression resulted in an increase in the hypoxia-induced IL-8 expression, whereas the inhibition of ras by transfection of dominant-negative ras inhibited the hypoxia-induced IL-8 expression.


CONCLUSIONS
These results show that hypoxia activates ras, PI3K/Akt pathway, and p38 MAPK pathway to enhance IL-8 gene transcription under hypoxia, and suggest these signaling pathways as potential targets for controlling IL-8 expression and angiogenesis by human ovarian carcinoma cells.
Xu
Lei
L
Edwin L. Steele Laboratory, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Pathak
Pooja S
PS
Fukumura
Dai
D
D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005799:Genes, Dominant; D017930:Genes, Reporter; D006801:Humans; D000860:Hypoxia; D016209:Interleukin-8 / Q000096:biosynthesis / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D016209:Interleukin-8; D012333:RNA, Messenger; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D008156:Luciferases; D011494:Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases