Glutathione S-transferase Mu 5 在膀胱癌細胞中發揮抗腫瘤活性  

李亞哲、沈正煌、周詠欽

嘉義基督教醫院 外科部 泌尿科

 Glutathione S-transferase Mu 5 Plays Anti-Tumor Activity in Bladder Cancer Cells

Ya-Che Lee, Cheng-Huang Shen, Yeong-Chin Jou

Divisions of Urology, Department of Surgery, Chiayi Christian Hospital

Introduction and Objectives:

Bladder cancer is the ninth most common cancer worldwide and the 13th most lethal cancer disease worldwide.Particularly, its high recurrence impairs patients’ quality of life and causes an enormous economic burden.  Therefore, it is important to prevent the development of bladder tumors by elucidating factors involved in their carcinogenesis and disease progression. Our previous report demonstrates that GSTM5 gene is highly CpG methylated in bladder cancer cell lines, and demethylation by 5-aza-dC activates GSTM5 gene expression. In the present study, we want to uncover the potential role of GSTM5 in bladder cancer cells. First, the DNA methylation level of GSTM5 gene was analyzed in human samples.

Materials & Methods:

DNA methylation was analyzed by DNA sequencing after bisulfite conversion-PCR. The cell viability was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell migration was assayed by wound healing and transwell analysis. Other functional assay included GST activity, GSH level assay, colony formation, cell adhesion assay and Western blot. From Oncomine data analysis, we found that GSTM5 mRNA expression was lower in bladder cancer tissues than in normal tissues. From the clinical samples we collected, the GSTM5 DNA methylation level was higher in 50 bladder cancer tissues than in 50 normal urine pellets. It suggests that GSTM5 expression is down-regulation in bladder cancers which might be the increase in DNA methylation-induced gene silence. In order to uncover the function of GSTM5 gene, it was overexpressed in a human bladder cancer cell line. Overexpression of GSTM5 in 5637 cells decreased cell proliferation rate, colony formation ability, cell metastasis, and cellular GSH concentration. After addition of GSH supplement, 5637 cells with GSTM5 overexpression reverses the ability of cell proliferation and metastasis. Buthionine sulfoximine, a GSH synthesis inhibitor, significantly decreased cellular GSH levels and cell survival in all 5637 cell lines. Buthionine sulfoximine also inhibits cell metastasis in wild-type 5637 and vector control cells, but not in GSTM5 overexpression cells because the metastatic activity is very low in the cells. GSTM5 overexpression also inhibited the adhesion of 5637 cells to extracellular matrix fibronectin.

Conclusions:

All above data supports that GSTM5 plays a tumor suppressor role in bladder cancer cells, and cellular decreased GSH level shows as a key mechanism for the cancer inhibition effect of GSTM5.