Wong Thian-Sze, Kwong Dora Lai-Wan, Sham Jonathan Shun-Tong, Wei William Ignace, Kwong Yok-Lam, Yuen Anthony Po-Wing
Department of Surgery, The University of Hong Kong, Hong Kong, China.
Clin Cancer Res. 2004 Apr 1;10(7):2401-6. doi: 10.1158/1078-0432.ccr-03-0139.
Gene-specific methylation is common in primary undifferentiated nasopharyngeal carcinoma (NPC). DNA released from apoptotic or necrotic cell death including those aberrantly methylated promoter DNA of cancer cells is absorbed into the circulation as cell-free plasma DNA of the patient. This study aims at evaluation of the potential use of methylated gene promoter DNA as a serological tumor marker of primary and potentially salvageable local or nodal recurrent NPC.
The quantity of plasma hypermethylated gene promoters of CDH1, DAPK1, p15, p16, RASSF1A, and MLH1 of 41 NPC patients before treatment and 43 normal individuals were studied using real-time quantitative PCR. The post-treatment plasma hypermethylated CDH1, DAPK1,and p16 were also measured in 13 NPC patients with locoregional recurrence and 17 patients in remission.
Concentrations of cell-free circulating DNA were significantly higher in NPC patients than normal controls (28.79 ng/ml versus 16.57 ng/ml, respectively). There was no significant difference in plasma DNA concentration of EBV-positive and -negative normal individuals. Methylated DNA was detectable in plasma of NPC patients before treatment including 46% for CDH1,42% for p16,20% for DAPK1,20% for p15,and 5% for RASSF1A. Hypermethylated MLH1 was not detected in plasma of all of the NPC patients and normal individuals. Aberrantly hypermethylated promoter DNA of at least one of the five genes was detectable in 29 of 41 (71%) plasma of NPC patients before treatment. Hypermethylated promoter DNA of at least one of the three genes (CDH1, DAPK1, and p16) was detectable in post-treatment plasma of 5 of 13 (38%) recurrent NPC patients and none of the patients in remission.
Our results suggested that cell-free circulating methylated gene promoter DNA is a possibly useful serological marker in assisting in screening of primary and potentially salvageable local or regional recurrent NPC.
基因特异性甲基化在原发性未分化鼻咽癌（NPC）中很常见。从凋亡或坏死性细胞死亡中释放的DNA，包括癌细胞那些异常甲基化的启动子DNA，会作为患者的游离血浆DNA被吸收进入循环系统。本研究旨在评估甲基化基因启动子DNA作为原发性以及可能可挽救的局部或淋巴结复发性NPC血清学肿瘤标志物的潜在用途。
采用实时定量PCR研究了41例NPC患者治疗前以及43名正常个体血浆中CDH1、DAPK1、p15、p16、RASSF1A和MLH1的高甲基化基因启动子的量。还对13例局部区域复发的NPC患者和17例缓解期患者治疗后的血浆中高甲基化的CDH1、DAPK1和p16进行了检测。
NPC患者中游离循环DNA的浓度显著高于正常对照组（分别为28.79 ng/ml和16.57 ng/ml）。EBV阳性和阴性的正常个体血浆DNA浓度无显著差异。在NPC患者治疗前的血浆中可检测到甲基化DNA，其中CDH1为46%，p16为42%，DAPK1为20%，p15为20%，RASSF1A为5%。在所有NPC患者和正常个体的血浆中均未检测到高甲基化的MLH1。41例NPC患者治疗前的血浆中有29例（71%）可检测到至少五个基因中一个基因的异常高甲基化启动子DNA。13例复发NPC患者治疗后的血浆中有5例（38%）可检测到至少三个基因（CDH1、DAPK1和p16）中一个基因的高甲基化启动子DNA，而缓解期患者均未检测到。
我们的结果表明，游离循环甲基化基因启动子DNA可能是一种有用的血清学标志物，有助于筛查原发性以及可能可挽救的局部或区域复发性NPC。
