Human breast cancer cell line MDA‐MB‐231 expresses endogenous A 2B adenosine receptors mediating a Ca 2+ signal

1 Two human breast cancer cell lines, MCF‐7 and MDA‐MB‐231, were screened for the presence of functionally significant adenosine receptor subtypes. 2 MCF‐7 cells did not contain adenosine receptors as judged by the lack of an effect of nonselective agonists on adenylyl cyclase activity or intracellular Ca 2+ levels. MDA‐MB‐231 cells showed both a stimulation of adenylyl cyclase and a PLC‐dependent increase in intracellular Ca 2+ in response to nonselective adenosine receptor agonists. 3 Both adenosine‐mediated responses in MDA‐MB‐231 cells were observed with the nonselective agonists 5′‐ N ‐ethylcarboxamidoadenosine (NECA) and 2‐(3‐hydroxy‐3‐phenyl)propyn‐1‐yladenosine‐5′‐ N ‐ethyluronamide (PHPNECA), but no responses were observed with agonists selective for A 1 , A 2A or A 3 adenosine receptors. The Ca 2+ signal was antagonized by 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX) and the nonselective antagonist 9‐ethyl‐8‐furyladenine (ANR 152), but not by A 2A or A 3 selective compounds. 4 In radioligand binding with [2‐ 3 H](4‐(2‐[7‐amino‐2‐(2‐furyl)[1,2,4]triazolo[2,3‐a][1,3,5]triazin‐5‐ylamino]ethyl)phenol) ([ 3 H]ZM 241385), a specific binding site with a K D value of 87 n M and a B max value of 1600 fmol mg −1 membrane protein was identified in membranes from MDA‐MB‐231 cells. 5 The pharmacological characteristics provide evidence for the expression of an A 2B adenosine receptor in MDA‐MB‐231 cells, which not only mediates a stimulation of adenylyl cyclase but also couples to a PLC‐dependent Ca 2+ signal, most likely via G q/11 . The A 2B receptor in such cancer cells may serve as a target to control cell growth and proliferation. 6 The selective expression of high levels of endogenous A 2B receptors coupled to two signaling pathways make MDA‐MB‐231 cells a suitable model for this human adenosine receptor subtype.British Journal of Pharmacology (2005) 145 , 211–218. doi: 10.1038/sj.bjp.0706180