Nishida Naoshi, Iwanishi Mina, Minami Tomohiro, Chishina Hirokazu, Arizumi Tadaaki, Takita Masahiro, Kitai Satoshi, Yada Norihisa, Ida Hiroshi, Hagiwara Satoru, Minami Yasunori, Ueshima Kazuomi, Sakurai Toshiharu, Kitano Masayuki, Kudo Masatoshi
Department of Gastroenterology and Hepatology, Kinki University School of Medicine, Osaka-Sayama, Osaka, Japan.
Dig Dis. 2015 Oct;33(6):745-50. doi: 10.1159/000439098. Epub 2015 Oct 21.
Several studies revealed that the proportion of hepatocellular carcinoma (HCC) without hepatitis virus infection (NBNC-HCC) is increasing. On the other hand, epigenetic alterations are reportedly responsible for HCC development. Here, we identified HCC risk factors that are associated with DNA methylation in the background liver tissue of NBNC-HCC patients.
We performed methylation analysis in 37 pairs of virus-positive and 22 pairs of NBNC-HCC and non-cancerous livers using a HumanMethylation450 BeadChip array. After the selection of differentially methylated CpGs (DM-CpGs) in cancerous and non-cancerous livers, we analyzed DNA methylation of DM-CpGs within the adjacent non-cancerous liver tissue that is affected by specific HCC risk factors.
A total of 38,331 CpGs were selected as DM-CpGs using the following criteria: difference of β-value between HCC and non-cancerous liver ≥0.15 and false discovery rate (FDR) q < 1.0E-12. We subsequently selected the DM-CpGs that had methylation differences with the background liver tissue (that has FDR q < 0.35). Among the virus-positive patients, the type of hepatitis virus was mostly associated with differences in methylation within the background liver tissues. However, we found that background methylation patterns were most significantly associated with aging in NBNC patients. Interestingly, age-related methylation differences in DM-CpGs were also observed in NBNC-HCC tissues.
Hepatitis viruses affect the methylation profiles within background liver tissues. However, difference in background methylation was mostly associated with age in NCBC-HCC patients; some age-related methylation events could contribute to emergence of NBNC-HCC in elderly individuals.
多项研究表明，无肝炎病毒感染的肝细胞癌（NBNC-HCC）比例正在上升。另一方面，据报道表观遗传改变与肝细胞癌的发生有关。在此，我们确定了与NBNC-HCC患者背景肝组织中DNA甲基化相关的肝细胞癌危险因素。
我们使用HumanMethylation450 BeadChip芯片对37对病毒阳性和22对NBNC-HCC及癌旁肝组织进行甲基化分析。在选择癌组织和癌旁肝组织中差异甲基化的CpG（DM-CpG）后，我们分析了受特定肝细胞癌危险因素影响的相邻癌旁肝组织中DM-CpG的DNA甲基化情况。
共选择了38,331个符合以下标准的CpG作为DM-CpG：肝细胞癌与癌旁肝组织之间的β值差异≥0.15且错误发现率（FDR）q < 1.0E-12。随后，我们选择了与背景肝组织存在甲基化差异（FDR q < 0.35）的DM-CpG。在病毒阳性患者中，肝炎病毒类型大多与背景肝组织内的甲基化差异有关。然而，我们发现背景甲基化模式在NBNC患者中与衰老最为显著相关。有趣的是，在NBNC-HCC组织中也观察到DM-CpG中与年龄相关的甲基化差异。
肝炎病毒影响背景肝组织中的甲基化谱。然而，在NCBC-HCC患者中，背景甲基化差异大多与年龄有关；一些与年龄相关的甲基化事件可能促使老年个体发生NBNC-HCC。
