title: A3 adenosine receptors modulate hypoxia-inducible factor-1alpha expression in human A375 melanoma cells.
abstract: Hypoxia-inducible factor-1 (HIF-1) is a key regulator of genes crucial to many aspects of cancer biology. The purine nucleoside, adenosine, accumulates within many tissues under hypoxic conditions, including that of tumors. Because the levels of both HIF-1 and adenosine are elevated within the hypoxic environment of solid tumors, we investigated whether adenosine may regulate HIF-1. Here we show that, under hypoxic conditions (< 2% O2), adenosine upregulates HIF-1alpha protein expression in a dose-dependent and time-dependent manner, exclusively through the A3 receptor subtype. The response to adenosine was generated at the cell surface because the inhibition of A3 receptor expression, by using small interfering RNA, abolished nucleoside effects. A3 receptor stimulation in hypoxia also increases angiopoietin-2 (Ang-2) protein accumulation through the induction of HIF-1alpha. In particular, we found that A3 receptor stimulation activates p44/p42 and p38 mitogen-activated protein kinases, which are required for A3-induced increase of HIF-1alpha and Ang-2. Collectively, these results suggest a cooperation between hypoxic and adenosine signals that ultimately may lead to the increase in HIF-1-mediated effects in cancer cells.
authors.affiliation: Department of Clinical and Experimental Medicine-Pharmacology Unit, University of Ferrara, Ferrara 44100, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Merighi
authors.forename: Annalisa
authors.initials: A
authors.lastname: Benini
authors.forename: Prisco
authors.initials: P
authors.lastname: Mirandola
authors.forename: Stefania
authors.initials: S
authors.lastname: Gessi
authors.forename: Katia
authors.initials: K
authors.lastname: Varani
authors.forename: Edward
authors.initials: E
authors.lastname: Leung
authors.forename: Stephen
authors.initials: S
authors.lastname: MacLennan
authors.forename: Pier Giovanni
authors.initials: PG
authors.lastname: Baraldi
authors.forename: Pier Andrea
authors.initials: PA
authors.lastname: Borea
mesh_terms: D000241:Adenosine / Q000737:chemistry / Q000378:metabolism; D042702:Angiopoietin-2 / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis*; D008545:Melanoma / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D043684:Receptor, Adenosine A3 / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D042702:Angiopoietin-2; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D043684:Receptor, Adenosine A3; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D000241:Adenosine; D010100:Oxygen