Schagdarsurengin U, Pfeifer G P, Dammann R
AWG Tumour Genetics of the Medical Faculty, Institute for Human Genetics, Martin-Luther-University Halle-Wittenberg, Halle/Saale, Germany.
Oncogene. 2007 May 10;26(21):3089-94. doi: 10.1038/sj.onc.1210107. Epub 2006 Nov 13.
Cystatin M is a potent endogenous inhibitor of lysosomal cysteine proteases. In breast carcinoma, cystatin M expression is frequently downregulated. It has been shown that cystatin M expression suppressed growth and migration of breast cancer cells. We examined the methylation status of the CpG island promoter of cystatin M in four breast cancer cell lines (MDAMB231, ZR75-1, MCF7 and T47D), in 40 primary breast carcinoma and in corresponding normal tissue probes by combined bisulphite restriction analysis. To investigate the effects of cystatin M expression on the growth of breast carcinoma, cystatin M was transfected in T47D. The cystatin M promoter was highly methylated in all four-breast cancer cell lines. Primary breast tumours were significantly more frequently methylated compared to normal tissue samples (60 vs 25%; P=0.006 Fisher's exact test). Treatment of breast cancer cells with 5-aza-2'-deoxycytidine (5-Aza-CdR), reactivated the transcription of cystatin M. Transfection of breast carcinoma cells with cystatin M caused a 30% decrease in colony formation compared to control transfection (P=0.002). Our results show that cystatin M is frequently epigenetically inactivated during breast carcinogenesis and cystatin M expression suppresses the growth of breast carcinoma. These data suggest that cystatin M may encode a novel epigenetically inactivated candidate tumour suppressor gene.
胱抑素M是溶酶体半胱氨酸蛋白酶的一种强效内源性抑制剂。在乳腺癌中，胱抑素M的表达经常下调。已有研究表明，胱抑素M的表达可抑制乳腺癌细胞的生长和迁移。我们通过联合亚硫酸氢盐限制分析，检测了四种乳腺癌细胞系（MDAMB231、ZR75-1、MCF7和T47D）、40例原发性乳腺癌以及相应正常组织样本中胱抑素M的CpG岛启动子的甲基化状态。为了研究胱抑素M表达对乳腺癌生长的影响，将胱抑素M转染至T47D细胞中。在所有四种乳腺癌细胞系中，胱抑素M启动子均高度甲基化。与正常组织样本相比，原发性乳腺肿瘤的甲基化频率显著更高（60%对25%；P=0.006，Fisher精确检验）。用5-氮杂-2'-脱氧胞苷（5-Aza-CdR）处理乳腺癌细胞，可重新激活胱抑素M的转录。与对照转染相比，用胱抑素M转染乳腺癌细胞导致集落形成减少30%（P=0.002）。我们的结果表明，在乳腺癌发生过程中，胱抑素M经常发生表观遗传失活，且胱抑素M的表达可抑制乳腺癌的生长。这些数据表明，胱抑素M可能编码一种新型的表观遗传失活候选肿瘤抑制基因。
