title: Stromal uptake and transmission of acid is a pathway for venting cancer cell-generated acid.
abstract: Proliferation and invasion of cancer cells require favorable pH, yet potentially toxic quantities of acid are produced metabolically. Membrane-bound transporters extrude acid from cancer cells, but little is known about the mechanisms that handle acid once it is released into the poorly perfused extracellular space. Here, we studied acid handling by myofibroblasts (colon cancer-derived Hs675.T, intestinal InMyoFib, embryonic colon-derived CCD-112-CoN), skin fibroblasts (NHDF-Ad), and colorectal cancer (CRC) cells (HCT116, HT29) grown in monoculture or coculture. Expression of the acid-loading transporter anion exchanger 2 (AE2) (SLC4A2 product) was detected in myofibroblasts and fibroblasts, but not in CRC cells. Compared with CRC cells, Hs675.T and InMyoFib myofibroblasts had very high capacity to absorb extracellular acid. Acid uptake into CCD-112-CoN and NHDF-Ad cells was slower and comparable to levels in CRC cells, but increased alongside SLC4A2 expression under stimulation with transforming growth factor β1 (TGFβ1), a cytokine involved in cancer-stroma interplay. Myofibroblasts and fibroblasts are connected by gap junctions formed by proteins such as connexin-43, which allows the absorbed acid load to be transmitted across the stromal syncytium. To match the stimulatory effect on acid uptake, cell-to-cell coupling in NHDF-Ad and CCD-112-CoN cells was strengthened with TGFβ1. In contrast, acid transmission was absent between CRC cells, even after treatment with TGFβ1. Thus, stromal cells have the necessary molecular apparatus for assembling an acid-venting route that can improve the flow of metabolic acid through tumors. Importantly, the activities of stromal AE2 and connexin-43 do not place an energetic burden on cancer cells, allowing resources to be diverted for other activities.
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom;
authors.forename: Alzbeta
authors.initials: A
authors.lastname: Hulikova
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom;
authors.forename: Nicholas
authors.initials: N
authors.lastname: Black
authors.affiliation: Cancer and Immunogenetics Laboratory, Weatherall Institute of Molecular Medicine, Department of Oncology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
authors.forename: Lin-Ting
authors.initials: LT
authors.lastname: Hsia
authors.affiliation: Cancer and Immunogenetics Laboratory, Weatherall Institute of Molecular Medicine, Department of Oncology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wilding
authors.affiliation: Cancer and Immunogenetics Laboratory, Weatherall Institute of Molecular Medicine, Department of Oncology, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom pawel.swietach@dpag.ox.ac.uk walter.bodmer@hertford.ox.ac.uk.
authors.forename: Walter F
authors.initials: WF
authors.lastname: Bodmer
authors.affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom; pawel.swietach@dpag.ox.ac.uk walter.bodmer@hertford.ox.ac.uk.
authors.forename: Pawel
authors.initials: P
authors.lastname: Swietach
mesh_terms: D000143:Acids / Q000633:toxicity; D049109:Cell Proliferation / Q000187:drug effects; D027963:Chloride-Bicarbonate Antiporters / Q000235:genetics; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018031:Connexin 43 / Q000235:genetics* / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D045325:HCT116 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D058628:Myofibroblasts / Q000378:metabolism / Q000473:pathology; D009361:Neoplasm Invasiveness / Q000235:genetics / Q000473:pathology; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000143:Acids; D027963:Chloride-Bicarbonate Antiporters; D018031:Connexin 43; C579496:SLC4A2 protein, human; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1
keywords: TGFβ1; anion exchanger 2; colorectal cancer; gap junctions; myofibroblast