Epidermal growth factor induces platelet-activating factor production through receptors transactivation and cytosolic phospholipase A2 in ovarian cancer cells.
BACKGROUND
Among the pro-inflammatory lipid mediators, platelet-activating factor (PAF) is a major primary and secondary messenger that binds to the PAF-receptor (PAFR). Epidermal growth factor (EGF) is a polypeptide growth factor that binds to the EGF-receptor (EGFR). Evidence suggests that both PAF and EGF play a significant role in oncogenic transformation, tumor growth, neoangiogenesis and metastasis, including ovarian cancer. PAF has the potential to transactivate EGFR in ovarian cancer cells. This study explores the mechanisms involved in EGF-induced PAF production.


METHODS
The effect of EGF on PAF production in ovarian cancer cells was observed using enzyme-linked immunosorbent assay. The receptors transactivation and the role of cytosolic phospholipase A2 (cPLA2) in modulating PAF production induced by EGF was assessed using pharmacological inhibitors, si-RNA knockdown, targeted gene overexpression and immunocytochemistry. The signaling pathways invovled in PAF production induced by EGF in ovarian cancer cells were assessed.


RESULTS
We demonstrate that EGF increases the production of PAF in CAOV3 and SKOV3 ovarian cancer cell lines. EGF induces the transactivation of PAFR, which can be blocked by an EGFR inhibitor. Inhibition of EGFR and/or PAFR blocks PAF production in response to EGF. EGF-induced PAF production involves the phosphorylation of extracellular-regulated protein kinase (ERK) and cytosolic phospholipase A2 (cPLA2). A cPLA2 inhibitor blocks EGF-induced PAF production as well as si-cPLA2, while overexpression of cPLA2 increases PAF production.


CONCLUSIONS
These results indicate that EGF stimulates PAF production in ovarian cancer cells in a manner that requires cPLA2. We have also determined that crosstalk can occur bidirectionally between EGFR and PAFR, suggesting that EGF-induced PAF production could result in positive feedback that acts on the PAF-receptor to promote ovarian cancer progression.
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Yi
Y
Yu
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Xiaoyan
X
Zhang
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Shanshan
S
Hong
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Mingxing
M
Zhang
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Qingqing
Q
Cai
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China.
Wei
W
Jiang
Obstetrics and Gynecology Hospital, Fudan University, No.419 Fang-Xie Road, Shanghai 200011, People's Republic of China ; Department of Obstetrics and Gynecology of Shanghai Medical School, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China ; Shanghai Key Laboratory of Female Reproductive Endocrine Related Diseases, No. 413 Zhao-Jiabang Road, Shanghai 200011, People's Republic of China ; Institute of Biomedical Sciences, Fudan University, No.138 Yi-Xueyuan Road, Shanghai 200032, People's Republic of China.
Congjian
C
Xu
D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000502:physiology*; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D054510:Phospholipases A2, Cytosolic / Q000378:metabolism*; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000096:biosynthesis*; D010980:Platelet Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D043562:Receptors, G-Protein-Coupled / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D015533:Transcriptional Activation
D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D054510:Phospholipases A2, Cytosolic
EGF; EGF-receptor; ERK; Ovarian cancer; PAF-receptor; cPLA2