Institute of Life Sciences, Jiangsu University, Zhenjiang, China.
Liver Int. 2010 May;30(5):703-14. doi: 10.1111/j.1478-3231.2010.02214.x. Epub 2010 Mar 8.
Delta-like 1 (DLK1), a fetal liver stem cell marker, is strongly expressed in human and rodent fetal liver, but not in adult liver. Notably, dysregulation of DLK1 was found in some human hepatocellular carcinomas (HCC). However, the effect of DLK1 on HCC cell growth and its underlying mechanism are still largely unknown.
To (i) assess the expression of DLK1 in human HCC and adjacent liver tissues and human HCC cell lines; (ii) evaluate the effect of DLK1 on SMMC-7721, Huh7 HCC cell growth in vitro and in vivo; and (iii) explore the potential mechanism of DLK1 that regulates HCC cell growth.
The expression of DLK1 mRNA and protein were detected using reverse transcriptase-polymerase chain reaction and immunohistochemistry respectively. The effect of DLK1 on the proliferation of SMMC-7721 and Huh7 cells was evaluated by colony formation and tumour xenograft assay. The differential expression profiles of DLK1-overexpressing SMMC-7721 cells and control cells were compared using HG-U133 Plus 2 Genechip. The cell cycle distribution of DLK1 forced expressing cells was comparatively analysed.
Upregulation of DLK1 was observed in 41 of 57 (71.9%) human HCC samples. Ectopic expression of DLK1 promoted cell proliferation, colony formation and tumorigenicity in SMMC-7721 and Huh7 cells. DLK1 upregulated the expression of interferon-inducible protein 16 (IFI16) and its promoter transcriptional activity, decreased p21waf1/cip1 and induced cell cycle acceleration. However, silencing of IFI16 using small interfering RNA abrogated DLK1-induced proliferation in these cells.
IFI16 may be an essential downstream target of DLK1 in HCC cells and required for DLK1-induced cell proliferation.
Delta-like 1（DLK1）是一种胎儿肝干细胞标志物，在人和啮齿动物的胎肝中强烈表达，但在成人肝中不表达。值得注意的是，DLK1 在一些人类肝细胞癌（HCC）中失调。然而，DLK1 对 HCC 细胞生长的影响及其潜在机制在很大程度上仍不清楚。
（i）评估 DLK1 在人 HCC 及相邻肝组织和人 HCC 细胞系中的表达；（ii）评估 DLK1 对 SMMC-7721、Huh7 HCC 细胞体外和体内生长的影响；（iii）探讨 DLK1 调节 HCC 细胞生长的潜在机制。
采用逆转录-聚合酶链反应和免疫组织化学分别检测 DLK1 mRNA 和蛋白的表达。通过集落形成和肿瘤异种移植实验评估 DLK1 对 SMMC-7721 和 Huh7 细胞增殖的影响。利用 HG-U133 Plus 2 Genechip 比较 DLK1 过表达 SMMC-7721 细胞和对照细胞的差异表达谱。比较 DLK1 强制表达细胞的细胞周期分布。
在 57 例 HCC 样本中，有 41 例（71.9%）观察到 DLK1 上调。DLK1 的异位表达促进了 SMMC-7721 和 Huh7 细胞的增殖、集落形成和致瘤性。DLK1 上调干扰素诱导蛋白 16（IFI16）及其启动子转录活性，降低 p21waf1/cip1 并诱导细胞周期加速。然而，用小干扰 RNA 沉默 IFI16 可消除 DLK1 在这些细胞中诱导的增殖。
IFI16 可能是 HCC 细胞中 DLK1 的一个重要下游靶标，也是 DLK1 诱导细胞增殖所必需的。
