Bodoor Khaldon, Haddad Yazan, Alkhateeb Asem, Al-Abbadi Abdullah, Dowairi Mohammad, Magableh Ahmad, Bsoul Nazzal, Ghabkari Abdulhameed
Department of Biology, Jordan University of Science and Technology, Irbid, Jordan E-mail :
Asian Pac J Cancer Prev. 2014;15(1):75-84. doi: 10.7314/apjcp.2014.15.1.75.
Aberrant DNA methylation of tumor suppressor genes has been reported in all major types of leukemia with potential involvement in the inactivation of regulatory cell cycle and apoptosis genes. However, most of the previous reports did not show the extent of concurrent methylation of multiple genes in the four leukemia types. Here, we analyzed six key genes (p14, p15, p16, p53, DAPK and TMS1) for DNA methylation using methylation specific PCR to analyze peripheral blood of 78 leukemia patients (24 CML, 25 CLL, 12 AML, and 17 ALL) and 24 healthy volunteers. In CML, methylation was detected for p15 (11%), p16 (9%), p53 (23%) and DAPK (23%), in CLL, p14 (25%), p15 (19%), p16 (12%), p53 (17%) and DAPK (36%), in AML, p14 (8%), p15 (45%), p53 (9%) and DAPK (17%) and in ALL, p15 (14%), p16 (8%), and p53 (8%). This study highlighted an essential role of DAPK methylation in chronic leukemia in contrast to p15 methylation in the acute cases, whereas TMS1 hypermethylation was absent in all cases. Furthermore, hypermethylation of multiple genes per patient was observed, with obvious selectiveness in the 9p21 chromosomal region genes (p14, p15 and p16). Interestingly, methylation of p15 increased the risk of methylation in p53, and vice versa, by five folds (p=0.03) indicating possible synergistic epigenetic disruption of different phases of the cell cycle or between the cell cycle and apoptosis. The investigation of multiple relationships between methylated genes might shed light on tumor specific inactivation of the cell cycle and apoptotic pathways.
在所有主要类型的白血病中均报道了肿瘤抑制基因的异常DNA甲基化，这可能与调节细胞周期和凋亡基因的失活有关。然而，之前的大多数报告并未显示这四种白血病类型中多个基因同时甲基化的程度。在此，我们使用甲基化特异性PCR分析了78例白血病患者（24例慢性粒细胞白血病、25例慢性淋巴细胞白血病、12例急性髓系白血病和17例急性淋巴细胞白血病）和24名健康志愿者外周血中六个关键基因（p14、p15、p16、p53、DAPK和TMS1）的DNA甲基化情况。在慢性粒细胞白血病中，检测到p15（11%）、p16（9%）、p53（23%）和DAPK（23%）甲基化；在慢性淋巴细胞白血病中，p14（25%）、p15（19%）、p16（12%）、p53（17%）和DAPK（36%）甲基化；在急性髓系白血病中，p14（8%）、p15（45%）、p53（9%）和DAPK（17%）甲基化；在急性淋巴细胞白血病中，p15（14%）、p16（8%）和p53（8%）甲基化。本研究强调了DAPK甲基化在慢性白血病中的重要作用，与急性白血病中的p15甲基化形成对比，而所有病例中均未出现TMS1高甲基化。此外，观察到每位患者存在多个基因的高甲基化，在9p21染色体区域基因（p14、p15和p16）中具有明显的选择性。有趣的是，p15甲基化使p53甲基化风险增加了五倍（p = 0.03），反之亦然，这表明细胞周期不同阶段或细胞周期与凋亡之间可能存在协同的表观遗传破坏。对甲基化基因之间多种关系的研究可能有助于揭示肿瘤特异性的细胞周期和凋亡途径失活情况。
