Juo-Han Lin1, Shih-Hsin Tu2,3,4, Li-Ching Chen2,3,5, Chi-Cheng Huang4,6,7, Hang-Lung Chang8, Tzu-Chun Cheng9, Hui-Wen Chang10, Chih-Hsiung Wu4,8, Han-Chung Wu11, Yuan-Soon Ho12,13,14,15. 1. Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei, Taiwan. 2. Breast Medical Center, Taipei Medical University Hospital, Taipei, Taiwan. 3. Taipei Cancer Center, Taipei Medical University, Taipei, Taiwan. 4. Department of Surgery, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. 5. TMU Research Center of Cancer Translational Medicine, Taipei Medical University, Taipei, Taiwan. 6. School of Medicine, College of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan. 7. Department of Surgery, Fu-Jen Catholic University Hospital, New Taipei City, Taiwan. 8. Department of General Surgery, En Chu Kong Hospital, New Taipei City, Taiwan. 9. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250 Wu-Hsing Street, Taipei, 110, Taiwan. 10. Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei, Taiwan. 11. Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan. 12. TMU Research Center of Cancer Translational Medicine, Taipei Medical University, Taipei, Taiwan. hoyuansn@tmu.edu.tw. 13. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, No. 250 Wu-Hsing Street, Taipei, 110, Taiwan. hoyuansn@tmu.edu.tw. 14. Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei, Taiwan. hoyuansn@tmu.edu.tw. 15. School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan. hoyuansn@tmu.edu.tw.
Abstract
PURPOSE: Glutathione S-transferase mu 3 (GSTM3) is an enzyme involving in the detoxification of electrophilic compounds by conjugation with glutathione. Higher GSTM3 mRNA levels were reported in patients with ERα-positive breast cancer who received only tamoxifen therapy after surgery. Thus, this study aimed to clarify the oncogenic characteristics of GSTM3 in breast cancer and the mechanism of tamoxifen resistance. METHODS: GSTM3 expression in human breast tumour tissues (n = 227) was analysed by RT-PCR and quantitative PCR. Western blot, promoter activity assays, and chromatin immunoprecipitation (ChIP) assays were used to investigate the mechanism of GSTM3 gene regulation. Hydrogen peroxide (H2O2)-induced cytotoxicity in breast cancer cells was detected by MTT assays and flow cytometry. The oncogenic characteristics of GSTM3 in MCF-7 cells were examined by siRNA knockdown in soft agar assays and a xenograft animal model. RESULTS: GSTM3 mRNA was highly expressed in ER- and HER2-positive breast cancers. Moreover, patients who received adjuvant Herceptin had increased GSTM3 mRNA levels in tumour tissue. Oestrogen-activated GSTM3 gene expression through ERα-mediated recruitment of SP1, EP300, and AP-1 complexes. GSTM3-silenced MCF-7 cells were more sensitive to H2O2, with significantly inhibited proliferation and colony formation abilities. Tamoxifen-resistant (Tam-R) cells lacking GSTM3 showed enhanced sensitivity to H2O2, but this result was contrary to that obtained after short-term tamoxifen exposure. The animal model suggested that GSTM3 silencing might suppress the tumourigenic ability of MCF-7 cells and increase tumour cell apoptosis. CONCLUSIONS: ROS production is one mechanism by which cancer drugs kill tumour cells, and according to our evidence, GSTM3 may play an important role in preventing breast cancer treatment-induced cellular cytotoxicity.
PURPOSE:Glutathione S-transferase mu 3 (GSTM3) is an enzyme involving in the detoxification of electrophilic compounds by conjugation with glutathione. Higher GSTM3 mRNA levels were reported in patients with ERα-positive breast cancer who received only tamoxifen therapy after surgery. Thus, this study aimed to clarify the oncogenic characteristics of GSTM3 in breast cancer and the mechanism of tamoxifen resistance. METHODS:GSTM3 expression in humanbreast tumour tissues (n = 227) was analysed by RT-PCR and quantitative PCR. Western blot, promoter activity assays, and chromatin immunoprecipitation (ChIP) assays were used to investigate the mechanism of GSTM3 gene regulation. Hydrogen peroxide (H2O2)-induced cytotoxicity in breast cancer cells was detected by MTT assays and flow cytometry. The oncogenic characteristics of GSTM3 in MCF-7 cells were examined by siRNA knockdown in soft agar assays and a xenograft animal model. RESULTS:GSTM3 mRNA was highly expressed in ER- and HER2-positive breast cancers. Moreover, patients who received adjuvant Herceptin had increased GSTM3 mRNA levels in tumour tissue. Oestrogen-activated GSTM3 gene expression through ERα-mediated recruitment of SP1, EP300, and AP-1 complexes. GSTM3-silenced MCF-7 cells were more sensitive to H2O2, with significantly inhibited proliferation and colony formation abilities. Tamoxifen-resistant (Tam-R) cells lacking GSTM3 showed enhanced sensitivity to H2O2, but this result was contrary to that obtained after short-term tamoxifen exposure. The animal model suggested that GSTM3 silencing might suppress the tumourigenic ability of MCF-7 cells and increase tumour cell apoptosis. CONCLUSIONS:ROS production is one mechanism by which cancer drugs kill tumour cells, and according to our evidence, GSTM3 may play an important role in preventing breast cancer treatment-induced cellular cytotoxicity.
Entities:
Keywords:
Breast cancer; Glutathione S-transferase mu 3; Hydrogen peroxide; Oestrogen receptor; Tamoxifen resistance