p28GANK Prevents Degradation of Oct4 and Promotes Expansion of Tumor-Initiating Cells in Hepatocarcinogenesis
p28GANK Prevents Degradation of Oct4 and Promotes Expansion of Tumor-Initiating Cells in Hepatocarcinogenesis
复制标题
p28(GANK) 可防止 Oct4 降解并促进肝癌发生过程中肿瘤起始细胞的扩增。
DOI：
10.1053/j.gastro.2012.02.042
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发表时间：
2012-06-01
期刊：
影响因子：
29.4
通讯作者：
Wang, Hong-Yang
中科院分区：
文献类型：
--
作者：
Qian, You-Wen;Chen, Yao;Wang, Hong-Yang
背景与目的：肝细胞癌（HCC）被认为是由肿瘤起始细胞（T-IC）引起的，尽管对其干细胞样特性知之甚少。方法：我们使用免疫组织化学定量了130例人HCC样本中p28（GANK）（Gankyrin）、OV 6和Oct 4的水平。磁激活细胞分选用于分离OV 6（+）HCC细胞。通过定量逆转录聚合酶链反应、流式细胞术和球体形成来评价T-IC特性。我们使用免疫共沉淀试验来研究p28（GANK），Oct 4和WWP 2之间的相互作用。在非肥胖糖尿病小鼠和严重联合免疫缺陷小鼠中检查肿瘤发生和肺转移。研究结果：在HCC样本中，高水平的p28 GANK与OV 6（+）肿瘤细胞的扩增相关;高水平的p28（GANK）和OV 6的组合与HCC的进展相关。p28（GANK）主要表达于通过磁分选分离的肝T-IC和未分化的原发性HCC球状体中。T-IC中p28（GANK）水平的增加增加了它们在HCC样品中的百分比、干细胞基因的表达、自我更新潜力、体外化学抗性以及致瘤性和发展成小鼠肺转移的能力。相反，p28的敲低（GANK）降低了它们的T-IC特性。p28（GANK）可能通过阻止WWP 2对转录因子Oct 4的泛素化和降解来激活肝脏T-IC。为了支持这一概念，p28（GANK）水平与HCC样本中的Oct 4水平相关。结论：p28（GANK）通过阻止Oct 4的降解来激活和维持HCC中的肝脏T-IC。因此，p28抑制剂（GANK）可能被开发为抑制T-IC并减缓肿瘤进展。
BACKGROUND & AIMS: Hepatocellular carcinoma (HCC) is believed to arise from tumor-initiating cells (T-ICs), although little is known about their stem cell-like properties. METHODS: We quantified levels of p28(GANK) (Gankyrin), OV6, and Oct4 in 130 human HCC samples using immunohistochemistry. Magnetic-activated cell sorting was used to isolate OV6(+) HCC cells. T-IC properties were evaluated by quantitative reverse-transcription polymerase chain reaction, flow cytometry, and spheroid formation. We used a coimmunoprecipitation assay to study interactions among p28(GANK), Oct4, and WWP2. Tumorigenicity and pulmonary metastasis were examined in nonobese diabetic and severe combined immunodeficient mice. RESULTS: In HCC samples, high levels of p28GANK correlated with expansion of OV6(+) tumor cells; the combination of high levels of p28(GANK) and OV6 was associated with progression of HCC. p28(GANK) was predominantly expressed in liver T-ICs, isolated by magnetic sorting, and undifferentiated primary HCC spheroids. Increased levels of p28(GANK) in T-ICs increased their percentages in HCC samples, expression of stem cell genes, self-renewal potential, chemoresistance in vitro, and tumorigenicity and ability to develop into pulmonary metastases in mice. Conversely, knockdown of p28(GANK) reduced their T-IC properties. p28(GANK) likely activates liver T-ICs by impeding ubiquitination and degradation of the transcription factor Oct4 by WWP2. In support of this concept, levels of p28(GANK) correlated with those of Oct4 in HCC samples. CONCLUSIONS: p28(GANK) activates and maintains liver T-ICs in HCCs by preventing degradation of Oct4. Inhibitors of p28(GANK) might therefore be developed to inactivate T-ICs and slow tumor progression.