Baba Shahid M, Azad Niyaz A, Shah Zafar A, Pandith Arshad A, Jan Aleem, Aziz Sheikh A
Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, India.
Advanced Centre for Human Genetics, Sher-I-Kashmir Institute of Medical Sciences, Srinagar, India.
Cancer Res Treat. 2017 Jul;49(3):790-797. doi: 10.4143/crt.2016.108. Epub 2016 Dec 5.
The p15 gene exerts its influence as an inhibitor of cyclin-dependent kinases and is frequently associated with hematological malignancies. Inactivation of this gene through DNA methylation has been found to be the most prevalent epigenetic alteration reported, with a high frequency in all French-American-British subtypes of acute myeloid leukemias, including acute promyelocytic leukemia (APL). In this study,we investigated the prognostic significance of p15 gene promoter hypermethylation and its expression in APL patients of Kashmir (North India).
p15 gene promoter hypermethylation was conducted by methylation-specific polymerase chain reaction, while its subsequent expression analysiswas carried out by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR).
Of the 37 patients, 16 (43.2%) were found to have methylated p15 genes. Of these 16 cases, seven (43.8%) were methylated partially and nine (56.2%) were found to have complete methylation. Moreover, nine of the 37 patients (24.3%) who presented with leukocytosis at their baseline had complete p15 gene methylation as well (p < 0.05). Semiquantitative RT-PCR showed a complete loss of p15 expression in nine patients with complete methylation coupled with leukocytosis (p=0.031), while seven patients with partial methylation showed decreased p15 expression. Six patients relapsed during the maintenance phase of treatment and were found to have a completely methylated p15 gene and no p15 mRNA.
Complete methylation and loss of p15 gene expression causes susceptibility to relapse and decreased survival in APL patients. Thus, p15 promoter hypermethylation is a prospective prognostic indicator and a reliable clinical aid in assessment of patients with APL.
p15基因作为细胞周期蛋白依赖性激酶的抑制剂发挥作用，且常与血液系统恶性肿瘤相关。已发现该基因通过DNA甲基化失活是报道中最普遍的表观遗传改变，在急性髓系白血病的所有法美英亚型中频率都很高，包括急性早幼粒细胞白血病（APL）。在本研究中，我们调查了克什米尔地区（印度北部）APL患者中p15基因启动子高甲基化及其表达的预后意义。
采用甲基化特异性聚合酶链反应检测p15基因启动子高甲基化，随后通过半定量逆转录聚合酶链反应（RT-PCR）进行其表达分析。
37例患者中，16例（43.2%）p15基因发生甲基化。在这16例中，7例（43.8%）为部分甲基化，9例（56.2%）为完全甲基化。此外，37例基线时出现白细胞增多的患者中有9例（24.3%）也存在p15基因完全甲基化（p<0.05）。半定量RT-PCR显示，9例完全甲基化且伴有白细胞增多的患者p15表达完全缺失（p=0.031），而7例部分甲基化患者p15表达降低。6例患者在治疗维持期复发，发现其p15基因完全甲基化且无p15 mRNA。
p15基因的完全甲基化和表达缺失导致APL患者易复发且生存率降低。因此，p15启动子高甲基化是APL患者评估中的一个前瞻性预后指标和可靠的临床辅助指标。
