RESUMO
<p><b>OBJECTIVE</b>To investigate whether PTEN can increase sensitivity of Ishikawa cells, an endometrial carcinoma cell line, to doxorubicin.</p><p><b>METHODS</b>Ishikawa cells transfected by PTEN gene or not were separately treated with serial concentrations of doxorubicin. The sensitivity of cells to doxorubicin was determined by MTT assay. The cells were stained with Hoechst 33258 and examined under fluorescence microscope to determine cell apoptosis. Immunoprecipitation and Western blotting analysis were performed to evaluate the effects of doxorubicin on phosphorylation of Bad and Akt/PKB.</p><p><b>RESULTS</b>Doxorubicin induced cell death of the PTEN-transfected and non-transfected Ishikawa cells in a dose-dependent manner, but the cell death was more significant in PTEN-expressing clones than in parental Ishikawa cells. A low concentration of doxorubicin (0.1 micromol/L) did not affect cell apoptosis in PTEN-null Ishikawa cells, but it induced cell apoptosis in PTEN-expressing clones. A high concentration of doxorubicin (1 micromol/L) induced cell apoptosis in both cell lines. However, the percentage of apoptotic cells was higher in PTEN-expressing clones than that in parental Ishikawa cells. In the PTEN-expressing clones, expression of phospho-Akt/PKB and phospho-Bad (Ser-136) was down regulated. Doxorubicin reduced the levels of phospho-Akt/PKB and phospho-Bad (Ser-136) in both cell lines, but the most significant reduction occurred in the PTEN-expressing clones.</p><p><b>CONCLUSION</b>PTEN significantly enhances chemosensitivity of Ishikawa cells to doxorubicin. With PTEN expression, doxorubicin may exert apoptosis-induction activity by downregulation of the PI3k/Akt/PKB signaling pathway in Ishikawa cells.</p>