Ma Stephanie, Chan Kwok Wah, Lee Terence Kin-Wah, Tang Kwan Ho, Wo Jana Yim-Hung, Zheng Bo-Jian, Guan Xin-Yuan
Department of Clinical Oncology, The University of Hong Kong, Pokfulam, Hong Kong, China.
Mol Cancer Res. 2008 Jul;6(7):1146-53. doi: 10.1158/1541-7786.MCR-08-0035.
Recent efforts in our study of cancer stem cells (CSC) in hepatocellular carcinoma (HCC) have led to the identification of CD133 as a prominent HCC CSC marker. Findings were based on experiments done on cell lines and xenograft tumors where expression of CD133 was detected at levels as high as 65%. Based on the CSC theory, CSCs are believed to represent only a minority number of the tumor mass. This is indicative that our previously characterized CD133(+) HCC CSC population is still heterogeneous, consisting of perhaps subsets of cells with differing tumorigenic potential. We hypothesized that it is possible to further enrich the CSC population by means of additional differentially expressed markers. Using a two-dimensional PAGE approach, we compared protein profiles between CD133(+) and CD133(-) subpopulations isolated from Huh7 and PLC8024 and identified aldehyde dehydrogenase 1A1 as one of the proteins that are preferentially expressed in the CD133(+) subfraction. Analysis of the expression of several different ALDH isoforms and ALDH enzymatic activity in liver cell lines found ALDH to be positively correlated with CD133 expression. Dual-color flow cytometry analysis found the majority of ALDH(+) to be CD133(+), yet not all CD133(+) HCC cells were ALDH(+). Subsequent studies on purified subpopulations found CD133(+)ALDH(+) cells to be significantly more tumorigenic than their CD133(-)ALDH(+) or CD133(-)ALDH(-) counterparts, both in vitro and in vivo. These data, combined with those from our previous work, reveal the existence of a hierarchical organization in HCC bearing tumorigenic potential in the order of CD133(+)ALDH(+) > CD133(+)ALDH(-) > CD133(-)ALDH(-). ALDH, expressed along CD133, can more specifically characterize the tumorigenic liver CSC population.
我们近期对肝细胞癌（HCC）中癌症干细胞（CSC）的研究成果，已将CD133鉴定为一种重要的HCC CSC标志物。这些发现基于对细胞系和异种移植肿瘤所做的实验，其中检测到CD133的表达水平高达65%。基于CSC理论，CSC被认为仅占肿瘤块的少数。这表明我们之前鉴定的CD133(+) HCC CSC群体仍然是异质性的，可能由具有不同致瘤潜力的细胞亚群组成。我们推测，有可能通过其他差异表达标志物进一步富集CSC群体。使用二维PAGE方法，我们比较了从Huh7和PLC8024分离出的CD133(+)和CD133(-)亚群之间的蛋白质谱，并鉴定醛脱氢酶1A1为在CD133(+)亚组分中优先表达的蛋白质之一。对几种不同ALDH同工型的表达及肝细胞系中ALDH酶活性的分析发现，ALDH与CD133表达呈正相关。双色流式细胞术分析发现，大多数ALDH(+)细胞为CD133(+)，但并非所有CD133(+) HCC细胞都是ALDH(+)。随后对纯化亚群的研究发现，CD133(+)ALDH(+)细胞在体外和体内的致瘤性均显著高于其CD133(-)ALDH(+)或CD133(-)ALDH(-)对应细胞。这些数据与我们之前的研究结果相结合，揭示了HCC中存在一个具有致瘤潜力的层次结构，顺序为CD133(+)ALDH(+) > CD133(+)ALDH(-) > CD133(-)ALDH(-)。与CD133一起表达的ALDH能够更特异性地表征具有致瘤性的肝脏CSC群体。
