Transactivation of epidermal growth factor receptor through platelet-activating factor/receptor in ovarian cancer cells

Abstract

BackgroundWe previously identified platelet-activating factor receptor (PAFR) as being overexpressed in ovarian cancer and found that its ligand PAF evoked EGFR phosphorylation using the phospho-antibody microarray. Epidermal growth factor receptor (EGFR) are also overexpressed in ovarian cancer and contribute to the growth of ovarian cancer cells. Here, we investigated the mechanisms of crosstalk between PAFR and EGFR signaling in ovarian cancer cells to further determine whether the interaction between PAFR and EGFR synergistic contribute to the progression of ovarian cancer.MethodsExpression and localization of PAFR in several ovarian cancer cell lines were assessed by Western blot, realtime-PCR and immunofluorescence. The ovarian cancer cells were stimulated with PAF or PAF and in some experiments also pharmacological inhibitors. Phosphorylation of proteins in signaling pathways were measured by Western blot. HB-EGF concentrations of the supernatant from stimulated ovarian cancer cells were measured by enzyme-linked immunosorbent assay.ResultsOur data show that PAF increases EGFR phosphorylation through PAFR in a time- and dose- dependent manner in SKOV-3 ovarian cancer cells. This transactivation is dependent on phospholipase C-β and intracellular calcium signaling. This pathway is also Src tyrosine kinase- and metalloproteinase- dependent. PAF triggers EGFR activation through the increased heparin-binding EGF-like growth factor (HB-EGF) release in metalloprotease-dependent manner. Several studies involving EGFR transactivation through G-protein coupled receptor (GPCR) have demonstrated EGFR-dependent increase in ERK1/2 phosphorylation. Yet in SKOV-3 cells, PAF treatment also increases ERK1/2 phosphorylation in a EGFR-independent manner.ConclusionsThe results suggest that in SKOV-3 ovarian cancer cells, PAF transactivates EGFR and downstream ERK pathways, thus diversifying the GPCR-mediated signal. The crosstalk between PAFR and EGFR suggests a potentially important signaling linkage between inflammatory and growth factor signaling in ovarian cancer cells.

Transactivation of epidermal growth factor receptor through platelet-activating factor/receptor in ovarian cancer cells

“…Ligand-dependent mechanisms involve the release of EGFR agonists through the cleavage and shedding of membrane-associated precursors by proteinases of the ADAM family [47]. Ligand-independent mechanisms have been reported to involve intracellular molecules, including Src family kinases and Pyk2 [48,49]. In the SKOV-3 cells, we observed that Src inhibitors abolished the PAF-induced phosphorylation of the EGFR.…”

PAFR selectively mediates radioresistance and irradiation-induced autophagy suppression in prostate cancer cells

“…It has been reported to promote non-small cell lung cancer (NSCLC) progression and metastasis by initiating forward feedback loop between PAFR and STAT3 [ 10 ], and contributes to the malignant development of esophageal squamous cell carcinoma by stimulating PI3K/AKT activation [ 11 ]. PAFR can also induce chemotherapy resistance in ovarian cancer through transactivating of epidermal growth factor receptor (EGFR) [ 12 , 13 ]. In addition, LNCaP and PC-3 cells have been shown to produce PAF endogenously [ 14 ].…”

Platelet activating factor leads to initiation and promotion of breast cancer

“…Apart from this, G-proteins like Ral, Rap as well as other signaling molecules like PLCγPLD are regulated by PAF-R [45,46] . In ovarian cancer cells PAF promotes cancer progression through EGFR/ERK transactivation pathway as well as activates PKC pathway, which couples with activated ERK [47] . FAK and Paxillin are activated following PAF induction in human endothelial cells [48] while in non-cancerous cell lines such as neutrophils [49] and eosinophils [50] , it activates various protein kinases such as G-protein kinase, PKC as well as tyrosine protein kinase [48] .…”