Adenosine receptors in colon carcinoma tissues and colon tumoral cell lines: focus on the A(3) adenosine subtype.
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.
Gessi
Stefania
S
Department of Clinical and Experimental Medicine, Pharmacology Unit and Interdisciplinary Center for the Study of Inflammation, Ferrara, Italy.
Merighi
Stefania
S
Varani
Katia
K
Cattabriga
Elena
E
Benini
Annalisa
A
Mirandola
Prisco
P
Leung
Edward
E
Mac Lennan
Stephen
S
Feo
Carlo
C
Baraldi
Stefania
S
Borea
Pier Andrea
PA
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
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