Hallberg Andrea R, Vorrink Sabine U, Hudachek Danielle R, Cramer-Morales Kimberly, Milhem Mohammed M, Cornell Robert A, Domann Frederick E
a Interdisciplinary Graduate Program in Molecular and Cellular Biology; Graduate College ; The University of Iowa ; Iowa City , IA USA ;
Epigenetics. 2014 Dec;9(12):1641-7. doi: 10.4161/15592294.2014.988062.
Metastatic melanoma is a deadly treatment-resistant form of skin cancer whose global incidence is on the rise. During melanocyte transformation and melanoma progression the expression profile of many genes changes. Among these, a gene implicated in several steps of melanocyte development, TFAP2A, is frequently silenced; however, the molecular mechanism of TFAP2A silencing in human melanoma remains unknown. In this study, we measured TFAP2A mRNA expression in primary human melanocytes compared to 11 human melanoma samples by quantitative real-time RT-PCR. In addition, we assessed CpG DNA methylation of the TFAP2A promoter in these samples using bisulfite sequencing. Compared to primary melanocytes, which showed high TFAP2A mRNA expression and no promoter methylation, human melanoma samples showed decreased TFAP2A mRNA expression and increased promoter methylation. We further show that increased CpG methylation correlates with decreased TFAP2A mRNA expression. Using The Cancer Genome Atlas, we further identified TFAP2A as a gene displaying among the most decreased expression in stage 4 melanomas vs. non-stage 4 melanomas, and whose CpG methylation was frequently associated with lack of mRNA expression. Based on our data, we conclude that TFAP2A expression in human melanomas can be silenced by aberrant CpG methylation of the TFAP2A promoter. We have identified aberrant CpG DNA methylation as an epigenetic mark associated with TFAP2A silencing in human melanoma that could have significant implications for the therapy of human melanoma using epigenetic modifying drugs.
转移性黑色素瘤是一种致命的、对治疗耐药的皮肤癌，其全球发病率正在上升。在黑素细胞转化和黑色素瘤进展过程中，许多基因的表达谱会发生变化。其中，一个参与黑素细胞发育多个步骤的基因TFAP2A经常被沉默；然而，TFAP2A在人类黑色素瘤中沉默的分子机制仍然未知。在本研究中，我们通过定量实时逆转录聚合酶链反应（RT-PCR）测量了原代人黑素细胞与11个人类黑色素瘤样本中TFAP2A mRNA的表达。此外，我们使用亚硫酸氢盐测序评估了这些样本中TFAP2A启动子的CpG DNA甲基化。与显示高TFAP2A mRNA表达且无启动子甲基化的原代黑素细胞相比，人类黑色素瘤样本显示TFAP2A mRNA表达降低且启动子甲基化增加。我们进一步表明，CpG甲基化增加与TFAP2A mRNA表达降低相关。使用癌症基因组图谱，我们进一步确定TFAP2A是一个在4期黑色素瘤与非4期黑色素瘤中表达下降最明显的基因，其CpG甲基化经常与mRNA表达缺失相关。基于我们的数据，我们得出结论，人类黑色素瘤中TFAP2A的表达可通过TFAP2A启动子异常的CpG甲基化而沉默。我们已经确定异常的CpG DNA甲基化是与人类黑色素瘤中TFAP2A沉默相关的一种表观遗传标记，这可能对使用表观遗传修饰药物治疗人类黑色素瘤具有重要意义。
