Department of Laboratory Medicine, Zhongshan Hospital, Fudan University, 136 Yi Xue Yuan Road, Shanghai, 200032, People's Republic of China.
Department of Liver Surgery, Liver Cancer Institute, Zhongshan Hospital, Fudan University, Key Laboratory of Carcinogenesis and Cancer Invasion, Ministry of Education, 136 Yi Xue Yuan Road, Shanghai, 200032, People's Republic of China.
BMC Cancer. 2019 Aug 1;19(1):760. doi: 10.1186/s12885-019-5963-z.
The role of sphere-forming culture in enriching subpopulations with stem-cell properties in hepatocellular carcinoma (HCC) is unclear. The present study investigates its value in enriching cancer stem cells (CSCs) subpopulations and the mechanism by which HCC CSCs are maintained.
HCC cell lines and fresh primary tumor cells were cultured in serum-free and ultra-low attachment conditions to allow formation of HCC spheres. In vitro and in vivo experiments were performed to evaluate CSC characteristics. Expression levels of CSC-related genes were assessed by qRT-PCR and the correlation between sphere formation and clinical characteristics was investigated. Finally, gene expression profiling was performed to explore the molecular mechanism underlying HCC CSC maintenance.
We found that both cell lines and primary tumor cells formed spheres. HCC spheres possessed the capacity for self-renewal, proliferation, drug resistance, and contained different subpopulations of CSCs. Of interest, 500 sphere-forming Huh7 cells or 200 primary tumor cells could generate tumors in immunodeficient animals. Sphere formation correlated with size, multiple tumors, satellite lesions, and advanced stage. Further investigation identified that the PPARα-SCD1 axis plays an important role in maintenance of the CSC properties of HCC sphere cells by promoting nuclear accumulation of β-Catenin. Inhibition of SCD1 interfered with sphere formation, down-regulated expression of CSC-related markers, and reduced β-Catenin nuclear accumulation.
Sphere-forming culture can effectively enrich subpopulations with stem-cell properties, which are maintained through activation of the PPARα-SCD1 axis. Therefore, we suggest that targeting the SCD1-related CSC machinery might provide a novel insight into HCC treatment.
球体形成培养在富集肝癌（HCC）干细胞特性亚群中的作用尚不清楚。本研究旨在探讨其在富集肝癌癌干细胞（CSC）亚群中的价值，以及维持 HCC CSCs 的机制。
将 HCC 细胞系和新鲜原代肿瘤细胞在无血清和超低附着条件下培养，以允许 HCC 球体形成。进行体外和体内实验以评估 CSC 特征。通过 qRT-PCR 评估 CSC 相关基因的表达水平，并研究球体形成与临床特征之间的相关性。最后，进行基因表达谱分析以探讨维持 HCC CSC 的分子机制。
我们发现细胞系和原代肿瘤细胞均能形成球体。HCC 球体具有自我更新、增殖、耐药性的能力，并包含不同的 CSC 亚群。有趣的是，500 个球体形成的 Huh7 细胞或 200 个原代肿瘤细胞能够在免疫缺陷动物中生成肿瘤。球体形成与肿瘤大小、多灶性、卫星病变和晚期相关。进一步研究表明，PPARα-SCD1 轴通过促进β-Catenin 的核积累，在维持 HCC 球体细胞的 CSC 特性方面发挥重要作用。SCD1 的抑制作用干扰球体形成、下调 CSC 相关标志物的表达，并减少β-Catenin 的核积累。
球体形成培养可以有效地富集具有干细胞特性的亚群，这些特性通过激活 PPARα-SCD1 轴得以维持。因此，我们建议靶向 SCD1 相关的 CSC 机制可能为 HCC 的治疗提供新的思路。
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