title: Extracellular protonation modulates cell-cell interaction mechanics and tissue invasion in human melanoma cells.
abstract: Detachment of cells from the primary tumour precedes metastatic progression by facilitating cell release into the tissue. Solid tumours exhibit altered pH homeostasis with extracellular acidification. In human melanoma, the Na+/H+exchanger NHE1 is an important modifier of the tumour nanoenvironment. Here we tested the modulation of cell-cell-adhesion by extracellular pH and NHE1. MV3 tumour spheroids embedded in a collagen matrix unravelled the efficacy of cell-cell contact loosening and 3D emigration into an environment mimicking physiological confinement. Adhesive interaction strength between individual MV3 cells was quantified using atomic force microscopy and validated by multicellular aggregation assays. Extracellular acidification from pHe7.4 to 6.4 decreases cell migration and invasion but increases single cell detachment from the spheroids. Acidification and NHE1 overexpression both reduce cell-cell adhesion strength, indicated by reduced maximum pulling forces and adhesion energies. Multicellular aggregation and spheroid formation are strongly impaired under acidification or NHE1 overexpression. We show a clear dependence of melanoma cell-cell adhesion on pHeand NHE1 as a modulator. These effects are opposite to cell-matrix interactions that are strengthened by protons extruded via NHE1. We conclude that these opposite effects of NHE1 act synergistically during the metastatic cascade.
authors.affiliation: Institute of Physiology II, University of Münster, Münster, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Hofschröer
authors.affiliation: Institute of Physiology II, University of Münster, Münster, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Koch
authors.affiliation: Institute of Physiology II, University of Münster, Münster, Germany.
authors.forename: Florian Timo
authors.initials: FT
authors.lastname: Ludwig
authors.affiliation: Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, Department of Cell Biology, Nijmegen, The Netherlands.|David H. Koch Center for Applied Research of Genitourinary Cancers, The University of Texas MD Anderson Cancer Center, Houston, Texas, United States.|Cancer Genomics Center, CG Utrecht, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Friedl
authors.affiliation: Institute of Physiology II, University of Münster, Münster, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Oberleithner
authors.affiliation: Department of Gastroenterology, Hannover Medical School, Hannover, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
authors.affiliation: Institute of Physiology II, University of Münster, Münster, Germany.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Schwab
mesh_terms: D000143:Acids / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002449:Cell Aggregation; D002450:Cell Communication; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D024042:Collagen Type I / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008545:Melanoma / Q000473:pathology*; D008954:Models, Biological; D009361:Neoplasm Invasiveness; D011522:Protons; D000074082:Sodium-Hydrogen Exchanger 1 / Q000378:metabolism; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology
chemical_list: D000143:Acids; D015815:Cell Adhesion Molecules; D024042:Collagen Type I; D011522:Protons; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1