Deneberg Stefan, Kanduri Meena, Ali Dina, Bengtzen Sofia, Karimi Mohsen, Qu Ying, Kimby Eva, Mansouri Larry, Rosenquist Richard, Lennartsson Andreas, Lehmann Sören
Department of Internal Medicine/Hematology; Karolinska Institutet; Karolinska University Hospital Huddinge; Stockholm, Sweden.
Institute of Biomedicine; Department of Clinical Chemistry and Transfusion Medicine; Sahlgrenska University Hospital; Göteborg, Sweden.
Epigenetics. 2014 Jun;9(6):910-7. doi: 10.4161/epi.28603. Epub 2014 Mar 31.
A commonly deleted region in chronic lymphocytic leukemia (CLL) is the 11q22-23 region, which encompasses the ATM gene. Evidence suggests that tumor suppressor genes other than ATM are likely to be involved in CLL with del(11q). A microRNA (miR) cluster including the miR-34b and miR-34c genes is located, among other genes, within the commonly deleted region (CDR) at 11q. Interestingly, these miRs are part of the TP53 network and have been shown to be epigenetically regulated. In this study, we investigated the expression and methylation status of these miRs in a well-characterized cohort of CLL, including cases with/without 11q-deletion. We show that the miR-34b/c promoter was aberrantly hypermethylated in a large proportion of CLL cases (48%, 25/52 cases). miR-34b/c expression correlated inversely to DNA methylation (P = 0.003), and presence of high H3K37me3 further suppressed expression regardless of methylation status. Furthermore, increased miR-34b/c methylation inversely correlated with the presence of 11q-deletion, indicating that methylation and del(11q) independently silence these miRs. Finally, 5-azacytidine and trichostatin A exposure synergistically increased the expression of miR-34b/c in CLL cells, and transfection of miR-34b or miR-34c into HG3 CLL cells significantly increased apoptosis. Altogether, our novel data suggest that miR-34b/c is a candidate tumor suppressor that is epigenetically silenced in CLL.
慢性淋巴细胞白血病（CLL）中一个常见的缺失区域是11q22 - 23区域，该区域包含ATM基因。有证据表明，除ATM外，其他肿瘤抑制基因可能也参与了伴有11q缺失的CLL。一个包含miR - 34b和miR - 34c基因的微小RNA（miR）簇，与其他基因一起，位于11q的常见缺失区域（CDR）内。有趣的是，这些miR是TP53网络的一部分，并且已被证明受到表观遗传调控。在本研究中，我们调查了这些miR在一组特征明确的CLL患者中的表达和甲基化状态，包括有/无11q缺失的病例。我们发现，在大部分CLL病例（48%，25/52例）中，miR - 34b/c启动子异常高甲基化。miR - 34b/c的表达与DNA甲基化呈负相关（P = 0.003），并且无论甲基化状态如何，高H3K37me3的存在都会进一步抑制其表达。此外，miR - 34b/c甲基化增加与11q缺失的存在呈负相关，表明甲基化和11q缺失独立地使这些miR沉默。最后，5 - 氮杂胞苷和曲古抑菌素A处理协同增加了CLL细胞中miR - 34b/c的表达，并且将miR - 34b或miR - 34c转染到HG3 CLL细胞中显著增加了细胞凋亡。总之，我们的新数据表明，miR - 34b/c是一种候选肿瘤抑制因子，在CLL中通过表观遗传机制沉默。
