Abstract: Correlation of GST-π and Topo ⅡExpression with the Chemosensitivity of Human BreastCancer Cells in vitroTong YANG1, Gang HE1, Qingguo FU1, Jixia YU2, Rong HUANG2, Keqiang LI3Corresponding author: Yang Tong, E-mail:tongyang1@163.com1Department of Oncological Surgery, The Second Hospital of Ningbo City, Ningbo 315010, China2Department of Pathology, The Second Hospital of Ningbo City, Ningbo 315010, China3The Central Laboratory, The Second Hospital of Ningbo City, Ningbo 315010, ChinaAbstract Objective: To investigate the correlation of GST-π and Topo Ⅱ expression with the chemosensitivity of breast cancercells in vitro. Methods: ATP-tumor chemosensitivity assay ( ATP-TCA ) was used to determine the effect of 4 single chemotherapeuticsEpirubicin ( EPI ), Paclitaxel ( PTX ), Taxotere ( TXT ), and Gemcitabine ( GEM ) and 2 combined regimens Epirubicin + Taxotere(EPI + TXT ), Cyclophosphamide + Epirubicin + 5-Fluorouracil ( CEF ) of in vitro breast cancer cells from 45 breast cancer patients.Expression of GST-π and Topo Ⅱ was examined by immunohistrochemistry. Results: ATP-TCA showed that the inhibitory rates ofEPI, PTX, TXT and GFM for breast cancer cell growth were 62.2 %, 35.6 %, 8.9 %, and 15.6 %, respectively. The inhibitory rates ofEPI+TXT and CEF were 77.8 % and 73.3 %, respectively, higher than those of PTX, TXT, and GEM ( P < 0.01 ). Immunohistochemis-try showed that the expression rates of GST-π and TopoⅡ were 44.4 % ( 20/45 ) and 62.2 % ( 28/45 ), respectively. EPI, EPI+TXT andCEF showed higher inhibitory rate in cases with Topo Ⅱ expression or in cases without GST-π expression ( P < 0.01 ). Conclusion:ATP-TCA combined with detection of GST-π and TopoⅡexpression can be used to screen effective therapeutics against breast cancer.Keywords Breast cancer; Chemosensitivity; GST-π; TopoⅡ