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

Abstract

Two human breast cancer cell lines, MCF-7 and MDA-MB-231, were screened for the presence of functionally significant adenosine receptor subtypes. 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. 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. In radioligand binding with [2- 3H](4-(2-[7- amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol) ([ 3H]ZM 241385), a specific binding site with a K D value of 87 nM and a B max value of 1600 fmol mg -1 membrane protein was identified in membranes from MDA-MB-231 cells. 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. 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. © 2005 Nature Publishing Group. All rights reserved.