title: Adenosine receptors in colon carcinoma tissues and colon tumoral cell lines: focus on the A(3) adenosine subtype.
abstract: Adenosine may affect several pathophysiological processes, including cellular proliferation, through interaction with A(1), A(2A), A(2B), and A(3) receptors. In this study we characterized adenosine receptors in human colon cancer tissues and in colon cancer cell lines Caco2, DLD1, HT29. mRNA of all adenosine subtypes was detected in cancer tissues and cell lines. At a protein levels low amount of A(1), A(2A), and A(2B) receptors were detected, whilst the A(3) was the most abundant subtype in both cancer tissues and cells, with a pharmacological profile typical of the A(3) subtype. All the receptors were coupled to stimulation/inhibition of adenylyl-cyclase in cancer cells, with the exception of A(1) subtype. Adenosine increased cell proliferation with an EC(50) of 3-12 microM in cancer cells. This effect was not essentially reduced by adenosine receptor antagonists. However dypiridamol, an adenosine transport inhibitor, increased the stimulatory effect induced by adenosine, suggesting an action at the cell surface. Addition of adenosine deaminase makes the A(3) agonist 2-chloro-N6-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine (Cl-IB-MECA) able to stimulate cell proliferation with an EC(50) of 0.5-0.9 nM in cancer cells, suggesting a tonic proliferative effect induced by endogenous adenosine. This effect was antagonized by 5-N-(4-methoxyphenyl-carbamoyl)amino-8-propyl-2(2furyl)-pyrazolo-[4,3e]-1,2,4-triazolo [1,5-c] pyrimidine (MRE 3008F20) 10 nM. Cl-IB-MECA-stimulated cell proliferation involved extracellular-signal-regulated-kinases (ERK1/2) pathway, as demonstrated by reduction of proliferation with 1,4-diamino-2,3-dicyano-1,4-bis-[2-amino-phenylthio]-butadiene (U0126) and by ERK1/2 phosphorylation. In conclusion this study indicates for the first time that in colon cancer cell lines endogenous adenosine, through the interaction with A(3) receptors, mediates a tonic proliferative effect.
authors.affiliation: Department of Clinical and Experimental Medicine, Pharmacology Unit and Interdisciplinary Center for the Study of Inflammation, Ferrara, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Gessi
authors.forename: Stefania
authors.initials: S
authors.lastname: Merighi
authors.forename: Katia
authors.initials: K
authors.lastname: Varani
authors.forename: Elena
authors.initials: E
authors.lastname: Cattabriga
authors.forename: Annalisa
authors.initials: A
authors.lastname: Benini
authors.forename: Prisco
authors.initials: P
authors.lastname: Mirandola
authors.forename: Edward
authors.initials: E
authors.lastname: Leung
authors.forename: Stephen
authors.initials: S
authors.lastname: Mac Lennan
authors.forename: Carlo
authors.initials: C
authors.lastname: Feo
authors.forename: Stefania
authors.initials: S
authors.lastname: Baraldi
authors.forename: Pier Andrea
authors.initials: PA
authors.lastname: Borea
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism* / Q000473:pathology*; D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D015153:Blotting, Western; D018938:Caco-2 Cells; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology*; D000242:Cyclic AMP / Q000378:metabolism; D019073:HT29 Cells; D006801:Humans; D008024:Ligands; D011869:Radioligand Assay; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D043705:Receptor, Adenosine A2A / Q000378:metabolism; D043704:Receptor, Adenosine A2B / Q000378:metabolism; D043684:Receptor, Adenosine A3 / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D008024:Ligands; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; D043704:Receptor, Adenosine A2B; D043684:Receptor, Adenosine A3; D000242:Cyclic AMP; D000241:Adenosine; D013936:Thymidine; C090034:2-chloro-N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide