title: Chronic acidosis in the tumour microenvironment selects for overexpression of LAMP2 in the plasma membrane.
abstract: Early cancers are avascular and hence, profoundly acidic. Pre-malignant cells must adapt to acidosis to thrive in this hostile microenvironment. Here, we investigate MCF-7 cells that are adapted to grow in acidic conditions using SILAC proteomics and we reveal a significant upregulation of lysosomal proteins. Prominent among these is LAMP2 that functions to protect lysosomal membranes from acid proteolysis. LAMP2 upregulation by acidosis is confirmed both in vitro and in vivo. Furthermore, we show that the depletion of LAMP2 is sufficient to increase acidosis-mediated toxicity. In breast cancer patient samples, there is a high correlation of LAMP2 mRNA and protein expression with progression. We also observe that LAMP2 is located at the plasma membrane in clinical samples and this redistribution is acid-induced in vitro. Our findings suggest a potential adaptive mechanism, wherein cells chronically exposed to an acidic environment translocate lysosomal proteins to their surface, thus protecting the plasmalemma from acid-induced hydrolysis.
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Damaghi
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Narges K
authors.initials: NK
authors.lastname: Tafreshi
authors.affiliation: Analytic Microscopy Core, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Lloyd
authors.affiliation: Department of Proteomics, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Sprung
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Veronica
authors.initials: V
authors.lastname: Estrella
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Wojtkowiak
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: David L
authors.initials: DL
authors.lastname: Morse
authors.affiliation: Department of Proteomics, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.|Department of Molecular Oncology, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Koomen
authors.affiliation: Analytic Microscopy Core, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.|Department of Anatomic Pathology, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Marilyn M
authors.identifier: http://orcid.org/0000-0003-4963-2255
authors.initials: MM
authors.lastname: Bui
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Gatenby
authors.affiliation: Department of Cancer Imaging and Metabolism, Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, Florida 33612, USA.
authors.forename: Robert J
authors.identifier: http://orcid.org/0000-0002-8888-7747
authors.initials: RJ
authors.lastname: Gillies
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D052119:Lysosomal-Associated Membrane Protein 2 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000378:metabolism*; D009374:Neoplasms, Experimental / Q000378:metabolism; D040081:Protein Array Analysis; D040901:Proteomics
chemical_list: D014408:Biomarkers, Tumor; C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2