Regulating role of STAT3 to HSP27 and cª²MYC expression in breast cancer

    SUN Zhengª²Kui, YAO Zhenª²Xiang, LIU Shengª²Chun

    Department of General Surgery, First Affiliated Hospital, Chongqing University of Medical Sciences, Chongqing 400016, China

    ¡¾Abstract¡¿ AIM: To investigate the regulating role of signal transducer and activator of transcription 3 (STAT3) to 27 ku heat shock protein (HSP27) and cª²MYC expression in breast cancer. METHODS: Expressions of STAT3, HSP27 and cª²MYC were examined in primary breast infiltrating duct carcinoma tissues of 51 patients using immunohistochemistry. Correlations between STAT3 expression and HSP27 or cª²MYC expression were analyzed with statistic method. After the transfection of MDAª²MBª²435S human breast carcinoma cells with STAT3 decoy oligodeoxynucleotides (Decoy ODNs), expressions of HSP27 and cª²MYC of MDAª²MBª²435S were semiª²quantified by Western blot, the apoptosis and the cell cycle distribution of MDAª²MBª²435S cells were analyzed with flow cytometry and proliferation of MDAª²MBª²435S cells was analyzed by MTT assay. RESULTS: In primary breast infiltrating duct carcinoma tissues, STAT3 expression was correlated positively with HSP27 expression and cª²MYC expression respectively (rs=0.454, P=0.001; rs=0.541, P=0.000). As the result of STAT3 inhibition by STAT3 Decoy ODNs in MDAª²MBª²435S cells, expressions of HSP27 and cª²MYC were markedly reduced, which was consistent with STAT3 activation reduction (Both P<0.01). The cell cycle progression of MDAª²MBª²435S cells was significantly inhibited at G0/G1 phase, the apoptosis of those cells was augmented and their proliferation was inhibited (P<0.01). CONCLUSION: Constitutively activated STAT3 may upª²regulate HSP27 and cª²MYC expression to inhibit breast cancer cell apoptosis and to facilitate their proliferation, thus leading to the malignancy of breast cancer cells. ......