Clinic for oncology, hematology and stem cell transplantation, Universitätsklinikum Aachen, RWTH Aachen, Pauwelsstraße 30, Aachen, 52074, Germany.
Clin Epigenetics. 2012 Aug 31;4(1):12. doi: 10.1186/1868-7083-4-12.
Secreted frizzled-related proteins (SFRPs) are antagonists of the Wnt signaling pathway, which plays a central role in stem cell maintenance and differentiation of stem cells and hematopoietic progenitors. Epigenetic downregulation of SFRPs by promoter hypermethylation has been described to be involved in the pathogenesis of hematopoietic malignancies. There is an association between aberrant Wnt signaling and the established cancer stem cell concept. In contrast to BCR-ABL1-positive chronic myeloid leukemia CML, BCR-ABL1-negative myeloproliferative neoplasms (Ph-MPN) are characterized by the frequent occurrence of an autoactivating mutation in the JAK2 tyrosine kinase (JAK2V617F) or other mutations in the JAK-STAT pathway. However, pathogenetic mechanisms of JAK2 mutated or unmutated Ph-MPN remain not completely understood. We determined the promoter methylation status of SFRP-1, -2, -4, and -5 in 57 MPN patient samples by methylation-specific polymerase chain reaction (PCR) (MSP). JAK2V617F was assessed by allele-specific PCR.
Aberrant methylation among primary MPN samples was 4% for SFRP-1, 25% for SFRP-2, 2% for SFRP-4, and 0% for SFRP-5. Hypermethylation of SFRP-2, which was the most frequently hypermethylated gene in our study, could not be correlated to any specific MPN subtype. However, we detected a significant correlation between SFRP-2 methylation and presence of a JAK2V617F mutation (P = 0.008). None of the 10 CML samples showed any SFRP-methylation.
Our data indicate that epigenetic dysregulation of the Wnt signaling pathway is a common event in MPN with aberrant methylation of at least one SFRP being detected in 25% of the primary patient samples and in 30% if only accounting for Ph-MPN. A significant correlation between SFRP-2 methylation and presence of JAK2V617F in our data supports the hypothesis that epigenetic dysregulation may be a complementary mechanism to genetic aberrations. Aberrant methylation of crucial stem cell maintenance genes seems to contribute to disease pathogenesis in Ph-MPN.
分泌卷曲相关蛋白（SFRPs）是 Wnt 信号通路的拮抗剂，该通路在干细胞维持和造血祖细胞的分化中起核心作用。启动子超甲基化导致 SFRP 的表观遗传下调，被认为参与了造血恶性肿瘤的发病机制。异常的 Wnt 信号与已确立的癌症干细胞概念之间存在关联。与 BCR-ABL1 阳性慢性髓性白血病（CML）相比，BCR-ABL1 阴性骨髓增殖性肿瘤（Ph-MPN）的特征是 JAK2 酪氨酸激酶（JAK2V617F）的自动激活突变或 JAK-STAT 通路中的其他突变频繁发生。然而，JAK2 突变或未突变 Ph-MPN 的发病机制仍不完全清楚。我们通过甲基化特异性聚合酶链反应（MSP）（MSP）确定了 57 例 MPN 患者样本中 SFRP-1、-2、-4 和-5 的启动子甲基化状态。通过等位基因特异性 PCR（allele-specific PCR）评估 JAK2V617F。
原发性 MPN 样本中存在异常甲基化，SFRP-1 为 4%，SFRP-2 为 25%，SFRP-4 为 2%，SFRP-5 为 0%。我们研究中最常发生甲基化的基因 SFRP-2 的 hypermethylation 与任何特定的 MPN 亚型均无相关性。然而，我们检测到 SFRP-2 甲基化与 JAK2V617F 突变的存在之间存在显著相关性（P=0.008）。我们的 10 例 CML 样本均未显示任何 SFRP 甲基化。
我们的数据表明，Wnt 信号通路的表观遗传失调是 MPN 的常见事件，至少有 25%的原发性患者样本中存在至少一种 SFRP 的异常甲基化，如果仅考虑 Ph-MPN，则有 30%的样本存在异常甲基化。我们的数据中 SFRP-2 甲基化与 JAK2V617F 的存在之间存在显著相关性，支持了表观遗传失调可能是遗传异常的补充机制的假说。关键的干细胞维持基因的异常甲基化似乎有助于 Ph-MPN 的发病机制。
