RT Journal Article SR Electronic T1 STI571 as a Potent Inhibitor of Growth and Invasiveness of Human Epithelial Breast Cancer Cells JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 1445 OP 1448 VO 24 IS 3A A1 A.E. ROUSSIDIS A1 T.N. MITROPOULOU A1 A.D. THEOCHARIS A1 C. KIAMOURIS A1 S. PAPADOPOULOS A1 D. KLETSAS A1 N.K. KARAMANOS YR 2004 UL http://ar.iiarjournals.org/content/24/3A/1445.abstract AB STI571, a specific tyrosine kinase inhibitor, exhibits a substantial therapeutic activity in patients with chronic myeloid leukaemia and gastrointestinal stromal tumors. In this study we examined the activity of STI571 on the growth and invasiveness of three human epithelial breast cancer cell lines of low (MCF-7) and high (ZR-75-1 and MDA-MB-231) invasive potential. Growth of all cell lines in serum-containing medium was significantly inhibited by STI571 in a dose-dependent manner, with an average IC50 of approximately 5-6 μM. Flow cytometric analysis revealed that this effect is characterized by an accumulation of all breast cancer cell types tested in the G2/M-phase of the cell cycle with a concomitant decrease of the percentage of cells in the S-phase. Interestingly, no increase in apoptosis was observed, indicating that the effect of this kinase inhibitor is cytostatic rather than cytotoxic. In addition, STI571 exerts a significant inhibition effect on the invasion of the highly invasive breast cancer cell lines ZR-75-1 and MDA-MB-231. These results encourage further preclinical investigations on the mechanisms underlying the inhibitory effects of STI571, which may be of great value in breast cancer treatment. Copyright© 2004 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved