en Clinical Biochemistry Clinical Biochemistry Original Research: Basic Science in Medicine Original Research: Basic Science in Medicine <p> <strong>ABSTRACT</strong></p><p> <strong>Background:</strong> The aims of this study were to assay the activity of adenosine deaminase (ADA) in estrogen receptor positive (MCF-7) and negative (MDA-MB468) breast cancer cell lines.</p><p> <strong>Methods:</strong> MDA-MB468 and MCF-7 breast cancer cell lines were cultured in complete medium, striped serum with and without 0.0 1~-LM diethylstilbestrol (DES), complete medium in the presence and absence of 111M tamoxifen for 20 hr. Adenosine deaminase activity was determined using the colorimetric method described by Guisti and Galanti.</p><p> <strong>Results:</strong> It was found that the activity of enzyme in estrogen receptor positive (ER+) cell line (MCF-7) was significantly higher than that of estrogen receptor negative breast cancer cell line (MDA-MB468). ADA activity in MCF-7 cells cultured in the presence of tamoxifen or charcoal-striped serum was significantly lower than that of control. Furthermore addition of diethylstilbestrol (DES) to the striped serum increased the value of ADA activity to that of control. Unlike MCF-7 cells, the activity of ADA in MDA-MB468 cells remained unchanged upon treatment with tamoxifen or striped serum.</p><p> <strong>Conclusion:</strong> These findings suggest estrogen responsiveness of ADA expression in MCF-7 cells.</p> Adenosine deaminase, breast cancer cell lines, estrogen receptor. 53 56 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-261&slc_lang=en&sid=1 MOHAMMAD HASHEMI mhdhash@yahoo.com 20031947532846006682 20031947532846006682 Yes Dept. of Clinical Biochemistry, Zahedan Medical University, Zahedan , Iran . FATEMEH KARAMI TEHRANI 20031947532846006683 20031947532846006683 No Cancer Research Lab, Dept. of Clinical Biochemistry, School of Medical Sciences, Tarbiat ModarresUniversity, Tehran, Iran. SAEID GHAVAMI 20031947532846006684 20031947532846006684 No Dept. of Clinical Biochemistry, School of Medicine, Zahedan Medical University, Zahedan, Iran, MAJID SIRATI SABET 20031947532846006685 20031947532846006685 No Dept. of Clinical Biochemistry, School of Medicine, Qazvin MedicalUniversity, Qazvin, Iran.