Alterations in gene expression associated with the overexpression of a splice variant of DNA methyltransferase 3b, DNMT3b4, during human hepatocarcinogenesis
Alterations in gene expression associated with the overexpression of a splice variant of DNA methyltransferase 3b, DNMT3b4, during human hepatocarcinogenesis
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DOI：
10.1007/s00432-004-0586-3
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发表时间：
2004-11-01
影响因子：
3.6
通讯作者：
Hirohashi, S
中科院分区：
文献类型：
--
作者：
Kanai, Y;Saito, Y;Hirohashi, S
目的：DNA甲基转移酶3b剪接变体DNMT3b4的过表达与中心体周围卫星区DNA低甲基化显著相关，已知在癌前病变和肝细胞癌（hcc）中，DNA低甲基化会导致着丝粒去浓缩和染色体重组增强。我们的目的是进一步阐明DNMT3b4在人肝癌发生中的意义。方法：采用生长速率测定、基因表达芯片和定量逆转录-聚合酶链反应（RT-PCR）对dnmt3b4转染的人上皮293细胞进行表征。RT-PCR还对8例正常肝脏标本、45例显示慢性肝炎或肝硬化（被认为是癌前病变）的非癌性肝脏标本和56例hcc进行了检测。结果：DNMT3b4转染体的生长速度是模拟转染体的两倍。在DNMT3b4转染物中，观察到干扰素信号效应因子信号换能器和转录激活因子1 （STAT1）的诱导，以及与这种信号传导有关的一组下游基因的诱导。DNMT3b4与STAT1在hcc中的mRNA表达水平有显著相关性。与正常肝脏标本相比，慢性肝炎和肝硬化标本中STAT1及3个下游基因mRNA表达水平均显著升高。在hcc中，未累及门静脉的肿瘤中STAT1及其下游基因的mRNA表达水平高于累及门静脉的恶性hcc。在组织样本中观察到STAT1 mRNA表达水平与各下游基因之间的显著相关性。结论：即使在癌前阶段，DNMT3b4的过表达不仅通过诱导染色体不稳定，还通过影响特定基因的表达参与了人类肝癌的发生。
Purpose: Overexpression of a splice variant of DNA methyltransferase 3b, DNMT3b4, correlates significantly with DNA hypomethylation in pericentromeric satellite regions, which is known to result in centromeric decondensation and enhanced chromosomal recombination in precancerous conditions and hepatocellular carcinomas (HCCs). We aimed to elucidate further the significance of DNMT3b4 during human hepatocarcinogenesis. Methods: DNMT3b4-transfected human epithelial 293 cells were characterized using growth rate measurements, gene expression microarray, and quantitative reverse transcription-polymerase chain reaction (RT-PCR) analyses. RT-PCR was also performed on eight normal liver specimens, 45 noncancerous liver specimens showing chronic hepatitis or cirrhosis, which are considered to be precancerous conditions, and 56 HCCs. Results: The growth rate of the DNMT3b4 transfectants was about double that of mock-transfectants. Induction of signal transducer and activator of transcription 1 (STAT1), an effector of interferon signaling, and of a set of downstream genes implicated in such signaling, was observed in the DNMT3b4 transfectants. There was significant correlation between the mRNA expression levels of DNMT3b4 and STAT1 in HCCs. mRNA expression levels of STAT1 and the three downstream genes examined were all significantly elevated in the chronic hepatitis and cirrhosis specimens compared with the normal liver specimens. Among the HCCs, the mRNA expression levels of STAT1 and the downstream genes were higher in tumors without portal vein involvement than in more malignant HCCs with portal vein involvement. Significant correlations between the mRNA expression levels of STAT1 and each of the downstream genes were observed in the tissue samples. Conclusions: Overexpression of DNMT3b4 is involved in human hepatocarcinogenesis, even at the precancerous stages, not only by inducing chromosomal instability but also by affecting the expression of specific genes.