EP2 prostanoid receptor promotes squamous cell carcinoma growth through epidermal growth factor receptor transactivation and iNOS and ERK1/2 pathways.
In squamous cell carcinoma, the levels of nitric oxide (NO) derived from inducible NO synthase (iNOS) and prostaglandin E2 (PGE2) derived from cyclooxygenase-2 (COX-2) originated from tumor cells or tumor-associated inflammatory cells have been reported to correlate with tumor growth, metastasis, and angiogenesis. The present study examined the role of the iNOS signaling pathway in PGE2-mediated tumor invasiveness and proliferation in squamous cell carcinoma, A431, and SCC-9 cells. Cell invasion and proliferation promoted by PGE2 were blocked by iNOS silencing RNA or iNOS/guanylate cyclase (GC) pharmacological inhibition. Consistently, iNOS-GC pathway inhibitors blocked mitogen-activated protein kinase-ERK1/2 phosphorylation, which was required to mediate PGE2 functions. In vivo, in A431 cells implanted in nude mice, GC inhibition also decreased the tumor proliferation index and ERK1/2 activation. PGE2 effects were confined to the selective stimulation of the EP2 receptor subtype, leading to epidermal growth factor receptor (EGFR) transactivation via protein kinase A (PKA) and c-Src activation. EP2-mediated ERK1/2 activation and cell functions were abolished by inhibitors of PKA, c-Src, and EGFR, as well as by inhibiting iNOS pathway. Silencing of iNOS also impaired EGFR-induced ERK1/2 phosphorylation. These results indicate that iNOS/GC signaling is a downstream player in the control of EP2/EGFR-mediated tumor cell proliferation and invasion.
Donnini
Sandra
S
Department of Molecular Biology, Pharmacology Angiogenesis Lab., University of Siena, Via Aldo Moro, 2, 53100, Siena, Italy.
Finetti
Federica
F
Solito
Raffaella
R
Terzuoli
Erika
E
Sacchetti
Andrea
A
Morbidelli
Lucia
L
Patrignani
Paola
P
Ziche
Marina
M
D002294:Carcinoma, Squamous Cell / Q000473:pathology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009569:Nitric Oxide / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D018078:Receptors, Prostaglandin E / Q000502:physiology*; D058307:Receptors, Prostaglandin E, EP2 Subtype; D011994:Recombinant Proteins / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
C545644:PTGER2 protein, human; C545645:Ptger2 protein, mouse; D034741:RNA, Small Interfering; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D011994:Recombinant Proteins; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D048052:Mitogen-Activated Protein Kinase 3