title: Linking of mPGES-1 and iNOS activates stem-like phenotype in EGFR-driven epithelial tumor cells.
abstract: Inflammatory prostaglandin E-2 (PGE-2) favors cancer progression in epithelial tumors characterized by persistent oncogene input. However, its effects on tumor cell stemness are poorly understood at molecular level. Here we describe two epithelial tumor cells A431 and A459, originating from human lung and skin tumors, in which epithelial growth factor (EGF) induces sequential up-regulation of mPGES-1 and iNOS enzymes, producing an inflammatory intracellular milieu. We demonstrated that concerted action of EGF, mPGES-1 and iNOS causes sharp changes in cell phenotype demonstrated by acquisition of stem-cell features and activation of the epithelial-mesenchymal transition (EMT). When primed with EGF, epithelial tumor cells transfected with mPGES-1 or iNOS to ensure steady enzyme levels display major stem-like and EMT markers, such as reduction in E-cadherin with a concomitant rise in vimentin, ALDH-1, CD133 and ALDH activity. Tumorsphere studies with these cells show increased sphere number and size, enhanced migratory and clonogenic capacity and sharp changes in EMT markers, indicating activation of this process. The concerted action of the enzymes forms a well-orchestrated cascade where expression of iNOS depends on overexpression of mPGES-1. Indeed, we show that through its downstream effectors (PGE-2, PKA, PI3K/Akt), mPGES-1 recruits non-canonical transcription factors, thus facilitating iNOS production. In conclusion, we propose that the initial event leading to tumor stem-cell activation may be a leveraged intrinsic mechanism in which all players are either inherent constituents (EGF) or highly inducible proteins (mPGES-1, iNOS) of tumor cells. We suggest that incipient tumor aggressiveness may be moderated by reducing pivotal input of mPGES-1.
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy. Electronic address: terzuoli8@unisi.it.
authors.forename: Erika
authors.initials: E
authors.lastname: Terzuoli
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy. Electronic address: finetti2@unisi.it.
authors.forename: Federica
authors.initials: F
authors.lastname: Finetti
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy. Electronic address: filomena.costanza@gmail.com.
authors.forename: Filomena
authors.initials: F
authors.lastname: Costanza
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy. Electronic address: okkamm@gmail.com.
authors.forename: Antonio
authors.initials: A
authors.lastname: Giachetti
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy; Istituto Toscano Tumori (ITT), 50136 Florence, Italy. Electronic address: marina.ziche@unisi.it.
authors.forename: Marina
authors.initials: M
authors.lastname: Ziche
authors.affiliation: Department of Life Sciences, University of Siena, 53100 Siena, Italy; Istituto Toscano Tumori (ITT), 50136 Florence, Italy. Electronic address: sandra.donnini@unisi.it.
authors.forename: Sandra
authors.initials: S
authors.lastname: Donnini
mesh_terms: D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000166:cytology; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology*; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D010641:Phenotype; D000071876:Prostaglandin-E Synthases / Q000378:metabolism*; D018874:Spheroids, Cellular / Q000166:cytology / Q000378:metabolism; D013234:Stem Cells; D014407:Tumor Cells, Cultured
chemical_list: C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; C512478:EGFR protein, human; D066246:ErbB Receptors; C000605862:PTGES protein, human; D000071876:Prostaglandin-E Synthases
keywords: EGF; Epithelial tumor cells; Stemness; Tumorspheres; iNOS; mPGES-1