Germline Duplication of SNORA18L5 Increases Risk for HBV-related Hepatocellular Carcinoma by Altering Localization of Ribosomal Proteins and Decreasing Levels of p53
Germline Duplication of SNORA18L5 Increases Risk for HBV-related Hepatocellular Carcinoma by Altering Localization of Ribosomal Proteins and Decreasing Levels of p53
复制标题
SNORA18L5 的种系重复通过改变核糖体蛋白的定位和降低 p53 的水平来增加 HBV 相关肝细胞癌的风险
DOI：
10.1053/j.gastro.2018.04.020
复制
发表时间：
2018-08-01
期刊：
影响因子：
29.4
通讯作者：
Zhou, Gangqiao
中科院分区：
文献类型：
--
作者：
Cao, Pengbo;Yang, Aiqing;Zhou, Gangqiao
背景与目标
单核苷酸多态性可能影响B型肝炎病毒（HBV）相关肝细胞癌（HCC）的风险。我们在中国血统人群中进行了一项基于生殖系拷贝数变异（CNV）的全基因组关联研究（GWAS），以寻找增加HCC风险的生殖系CNV。
方法
我们在中国人群中对1583例HCC病例（慢性HBV感染和HCC患者）和1540例对照（慢性HBV感染但无HCC患者）进行了基于CNV的GWAS。在L-02、HepG 2或TP 53-/-或野生型HCT 116细胞中表达鉴定的候选物，并在HepG 2、Bel-7402和SMMC-7721细胞中用短发夹RNA敲低;测量增殖、集落形成和凋亡。在裸鼠中监测来自细胞系的异种移植肿瘤的形成。通过免疫共沉淀、免疫荧光和免疫印迹分析研究核糖体蛋白的亚细胞定位和p53的水平或活性。通过定量逆转录聚合酶链反应定量小核仁RNA H/ACA盒18样5（SNORA 18 L5）的水平。
结果
我们发现染色体15q13.3处的低频率重复与HBV相关HCC的风险密切相关（总体P = 3.17 × 10-8;比值比，12.02）。15q13.3重复的拷贝数与肝组织中SNORA 18 L5的表达相关。SNORA 18 L5的过表达增加了小鼠中HCC细胞增殖和异种移植肿瘤的生长;敲低降低了HCC增殖和肿瘤生长。SNORA 18 L5在HepG 2和SMMC-7721细胞中的过表达抑制p53依赖的细胞周期阻滞和凋亡。SNORA 18 L5的过表达导致过度活跃的核糖体生物合成，增加成熟的18 S和28 S核糖体RNA的水平，并导致核糖体蛋白RPL 5和RPL 11留在核仁中，这使它们不能与MDM 2结合。这导致MDM 2介导的泛素化和p53降解增加。与非肿瘤肝组织相比，SNORA 18 L5在HCC组织中的水平增加，并且与患者的生存时间较短相关。
结论
在基于CNV的GWAS中，我们将15q13.3的重复与HBV相关HCC的风险增加相关联。我们发现SNORA 18 L5在这个位置可以促进小鼠肝癌细胞增殖和肿瘤生长。SNORA 18 L5增加核糖体生物合成，促进核糖体RNA成熟，并改变RPL 5和RPL 11的定位，从而增加MDM 2介导的p53蛋白水解和细胞周期停滞。
BACKGROUND & AIMS
Single nucleotide polymorphisms could affect risk for hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). We performed a germline copy number variation (CNV)-based genome-wide association study (GWAS) in populations of Chinese ancestry to search for germline CNVs that increase risk of HCC.
METHODS
We conducted a CNV-based GWAS of 1583 HCC cases (persons with chronic HBV infection and HCC) and 1540 controls (persons with chronic HBV infection without HCC) in Chinese populations. Identified candidates were expressed in L-02, HepG2, or TP53-/- or wild-type HCT116 cells, and knocked down with short hairpin RNAs in HepG2, Bel-7402, and SMMC-7721 cells; proliferation, colony formation, and apoptosis were measured. Formation of xenograft tumors from cell lines was monitored in nude mice. Subcellular localization of ribosome proteins and levels or activity of p53 were investigated by co-immunoprecipitation, immunofluorescence, and immunoblot analyses. Levels of small nucleolar RNA H/ACA box 18-like 5 (SNORA18L5) were quantified by quantitative reverse transcription polymerase chain reaction.
RESULTS
We identified a low-frequency duplication at chromosome 15q13.3 strongly associated with risk of HBV-related HCC (overall P = 3.17 × 10-8; odds ratio, 12.02). Copy numbers of the 15q13.3 duplication correlated with the expression of SNORA18L5 in liver tissues. Overexpression of SNORA18L5 increased HCC cell proliferation and growth of xenograft tumors in mice; knockdown reduced HCC proliferation and tumor growth. SNORA18L5 overexpression in HepG2 and SMMC-7721 cells inhibited p53-dependent cell cycle arrest and apoptosis. Overexpression of SNORA18L5 led to hyperactive ribosome biogenesis, increasing levels of mature 18S and 28S ribosomal RNAs and causing the ribosomal proteins RPL5 and RPL11 to stay in the nucleolus, which kept them from binding to MDM2. This resulted in increased MDM2-mediated ubiquitination and degradation of p53. Levels of SNORA18L5 were increased in HCC tissues compared with nontumor liver tissues and associated with shorter survival times of patients.
CONCLUSIONS
In a CNV-based GWAS, we associated duplication at 15q13.3 with increased risk of HBV-related HCC. We found SNORA18L5 at this location to promote HCC cell proliferation and tumor growth in mice. SNORA18L5 increases ribosome biogenesis, facilitates ribosomal RNA maturation, and alters localization of RPL5 and RPL11, allowing for increased MDM2-mediated proteolysis of p53 and cell cycle arrest.