Luo W, Wang X, Kageshita T, Wakasugi S, Karpf A R, Ferrone S
Department of Immunology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA.
Oncogene. 2006 May 11;25(20):2873-84. doi: 10.1038/sj.onc.1209319.
The human high molecular weight-melanoma associated antigen (HMW-MAA) is a membrane-bound chondroitin sulfate proteoglycan that is variably expressed in a high percentage of melanoma cell lines and tumors. Since the mechanism(s) regulating HMW-MAA expression has(ve) not been defined, in this study, we have examined whether promoter DNA methylation regulates the level of HMW-MAA expression. In melanoma cell lines, the level of HMW-MAA mRNA and protein expression is coordinately regulated, implicating a transcriptional control mechanism. Consistent with a role for regulation by DNA methylation, we have found that a dense CpG island flanks the human HMW-MAA gene transcriptional start site. Methylation-specific PCR and sodium bisulfite DNA sequencing analyses indicate that the HMW-MAA promoter is heavily methylated in melanoma cell lines, melanoma lesions and normal lymphocytes that do not express HMW-MAA; in contrast, the HMW-MAA promoter is not methylated in melanoma cell lines and tumors that express this antigen. In addition, HMW-MAA expression is markedly induced in HMW-MAA-negative melanoma cell lines by incubation with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine. In summary, our results establish DNA methylation as a key regulator of HMW-MAA expression by human melanoma cells. This information represents a useful background to optimize immunotherapeutic strategies targeting HMW-MAA.
人高分子量黑色素瘤相关抗原（HMW-MAA）是一种膜结合硫酸软骨素蛋白聚糖，在高比例的黑色素瘤细胞系和肿瘤中呈可变表达。由于调节HMW-MAA表达的机制尚未明确，在本研究中，我们检测了启动子DNA甲基化是否调节HMW-MAA的表达水平。在黑色素瘤细胞系中，HMW-MAA mRNA和蛋白表达水平受到协同调节，提示存在转录控制机制。与DNA甲基化调节作用一致，我们发现人HMW-MAA基因转录起始位点两侧有一个密集的CpG岛。甲基化特异性PCR和亚硫酸氢钠DNA测序分析表明，HMW-MAA启动子在不表达HMW-MAA的黑色素瘤细胞系、黑色素瘤病变组织和正常淋巴细胞中高度甲基化；相反，在表达该抗原的黑色素瘤细胞系和肿瘤中，HMW-MAA启动子未发生甲基化。此外，用DNA甲基转移酶抑制剂5-氮杂-2'-脱氧胞苷处理HMW-MAA阴性黑色素瘤细胞系后，HMW-MAA表达明显诱导。总之，我们的结果表明DNA甲基化是人黑色素瘤细胞中HMW-MAA表达的关键调节因子。这一信息为优化靶向HMW-MAA的免疫治疗策略提供了有用的背景。
