title: Anti-proliferative effect of atrial natriuretic peptide on colorectal cancer cells: evidence for an Akt-mediated cross-talk between NHE-1 activity and Wnt/β-catenin signaling.
abstract: Acidic tumor microenvironment and Wnt/β-catenin pathway activation have been recognized as two crucial events associated with the initiation and progression of cancer. The aim of this study was to clarify the molecular mechanisms underlying the anti-proliferative effects of atrial natriuretic peptide (ANP) as well as to investigate the relationship between the cellular pH and the Wnt/β-catenin signaling in cancer cells.To pursue our aims, we conducted investigations in DHD/K12/Trb rat colon adenocarcinoma cells. Intracellular pH was measured by Confocal Laser Scanning Microscopy (CLSM) using the lysosensor Green DND-189 probe. Expression of crucial molecules in the Wnt/β-catenin signaling pathway was analyzed by CLSM, western blot, and real time PCR. Measurements of activation (phosphorylation state) of Akt, ERK1/2, and p38MAPKinase were performed by Reverse-Phase Protein Microarray Analysis (RPMA).We showed that ANP triggered a NHE-1-mediated increase of the intracellular acidity, inhibiting the Wnt/β-catenin signaling simultaneously. Moreover, we observed that the Wnt1a, a Wnt signaling activator, affected the intracellular pH in an opposite fashion. Results from the comparative analysis of ANP and EIPA (a NHE-1 specific inhibitor) showed that these two molecules affect both the intracellular acidification and the Wnt/β-catenin signaling cascade. Specifically, ANP acts on the upstream of the cascade, through a Frizzled-mediated activation, while EIPA does on the downstream.We show for the first time that the Akt activity might be a relevant molecular event linking the NHE-1-regulated intracellular pH and the Wnt/β-catenin signaling. This provides evidence for a cross-talk between the intracellular alkalinization and the Wnt signaling in tumor cells.
authors.affiliation: Institute of Translational Pharmacology, National Research Council of Italy, Via Fosso del Cavaliere 100, 00133, Rome, Italy. annalucia.serafino@ift.cnr.it
authors.forename: Annalucia
authors.initials: A
authors.lastname: Serafino
authors.forename: Noemi
authors.initials: N
authors.lastname: Moroni
authors.forename: Rossana
authors.initials: R
authors.lastname: Psaila
authors.forename: Manuela
authors.initials: M
authors.lastname: Zonfrillo
authors.forename: Federica
authors.initials: F
authors.lastname: Andreola
authors.forename: Francesca
authors.initials: F
authors.lastname: Wannenes
authors.forename: Luana
authors.initials: L
authors.lastname: Mercuri
authors.forename: Guido
authors.initials: G
authors.lastname: Rasi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Pierimarchi
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020935:MAP Kinase Signaling System; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C452850:Slc9a1 protein, rat; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D051176:beta Catenin; D000584:Amiloride; D009320:Atrial Natriuretic Factor; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; C039614:ethylisopropylamiloride