Zhang Rui, Kang Kyoung Ah, Piao Mei Jing, Kim Ki Cheon, Zheng Jian, Yao Cheng Wen, Cha Ji Won, Maeng Young Hee, Chang Weon Young, Moon Pyong-Gon, Baek Moon-Chang, Hyun Jin Won
School of Medicine and Institute for Nuclear Science and Technology, Jeju National University, Jeju 690-756, Republic of Korea.
Department of Molecular Medicine, Cell and Matrix Biology Research Institute, School of Medicine, Kyungpook National University, Daegu 700-422, Republic of Korea.
Int J Oncol. 2014 Sep;45(3):1275-83. doi: 10.3892/ijo.2014.2522. Epub 2014 Jun 25.
Glutathione S-transferase π-1 (GSTP-1) is a member of the glutathione S-transferase enzyme superfamily, which catalyzes the conjugation of electrophiles to glutathione during the process of detoxification. In this study, the epigenetic alterations of GSTP-1 expression in human colorectal cancers and the underlying mechanisms were investigated. In 10 colon cancer patients, proteomic analysis revealed that expression of GSTP-1 protein was higher in tumor tissues than in paired adjacent normal tissues. Likewise, in 7 of 10 colon cancer patients, GSTP-1 protein expression was more than 1.5-fold higher in tumor tissues than in adjacent normal tissues, as determined by western blotting. Immunohistochemical data confirmed that GSTP-1 protein was expressed at higher levels in colon cancer tissues compared to normal mucosa. GSTP-1 enzyme activity was closely correlated with GSTP-1 protein expression in colon cancer patients. Consistent with this, GSTP-1 mRNA, protein and activity levels were higher in the colorectal cancer cell lines Caco-2, HCT-116, HT-29, SNU-407 and SNU-1033 compared to the normal colon cell line FHC. Methylation-specific PCR results indicated that the high levels of GSTP-1 in human colorectal cancer cell lines were likely due to the lower degree of promoter methylation in colon cancer cell lines compared to the normal colon cell line, consistent with findings in colon cancer patients. Moreover, the levels of specific activator-protein complexes and histone marks were higher in human colorectal cancer cells compared to the normal human colon cell line, whereas the repressor protein complexes exhibited the opposite pattern. Furthermore, chromatin immunoprecipitation assays demonstrated that expression levels of the transcription factors AP-1 and SP-1 were correlated with the upregulation of GSTP-1 expression in colorectal cancer cells. Finally, knockdown of GSTP-1 promoted the sensitivity of SNU-407 cells to the anticancer agent 5-fluorouracil. These data indicate that GSTP-1 may serve as a clinically useful biomarker of colon cancer and a target for anti-colon cancer drugs.
谷胱甘肽S-转移酶π-1（GSTP-1）是谷胱甘肽S-转移酶超家族的成员，在解毒过程中催化亲电试剂与谷胱甘肽的结合。在本研究中，对人结肠直肠癌中GSTP-1表达的表观遗传改变及其潜在机制进行了研究。在10例结肠癌患者中，蛋白质组学分析显示，肿瘤组织中GSTP-1蛋白的表达高于配对的相邻正常组织。同样，在10例结肠癌患者中的7例中，通过蛋白质印迹法测定，肿瘤组织中GSTP-1蛋白表达比相邻正常组织高1.5倍以上。免疫组织化学数据证实，与正常黏膜相比，GSTP-1蛋白在结肠癌组织中的表达水平更高。在结肠癌患者中，GSTP-1酶活性与GSTP-1蛋白表达密切相关。与此一致的是，与正常结肠细胞系FHC相比，结肠癌细胞系Caco-2、HCT-116、HT-29、SNU-407和SNU-1033中的GSTP-1 mRNA、蛋白和活性水平更高。甲基化特异性PCR结果表明，人结肠癌细胞系中GSTP-1的高水平可能是由于与正常结肠细胞系相比，结肠癌细胞系中启动子甲基化程度较低，这与结肠癌患者的研究结果一致。此外，与人正常结肠细胞系相比，人结肠癌细胞中特定激活蛋白复合物和组蛋白标记的水平更高，而阻遏蛋白复合物则呈现相反的模式。此外，染色质免疫沉淀试验表明，转录因子AP-1和SP-1的表达水平与结肠癌细胞中GSTP-1表达的上调相关。最后，敲低GSTP-1可提高SNU-407细胞对抗癌药物5-氟尿嘧啶的敏感性。这些数据表明，GSTP-1可能是结肠癌临床上有用的生物标志物和抗结肠癌药物的靶点。
