Ho Maria M, Ng Alvin V, Lam Stephen, Hung Jaclyn Y
Department of Cancer Genetics and Developmental Biology, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
Cancer Res. 2007 May 15;67(10):4827-33. doi: 10.1158/0008-5472.CAN-06-3557.
Stem cells have been isolated by their ability to efflux Hoechst 33342 dye and are referred to as the "side population" (SP). In this study, we used flow cytometry and Hoechst 33342 dye efflux assay to isolate and characterize SP cells from six human lung cancer cell lines (H460, H23, HTB-58, A549, H441, and H2170). Nonobese diabetic/severe combined immunodeficiency xenograft experiments showed that SP cells were enriched in tumor-initiating capability compared with non-SP cells. Matrigel invasion assay showed that SP cells also have higher potential for invasiveness. Further characterization of this SP phenotype revealed several stem cell properties. We found evidence for repopulating ability by SP to regenerate a population resembling the original population. SP displayed elevated expression of ABCG2 as well as other ATP-binding cassette transporters and showed resistance to multiple chemotherapeutic drugs. Human telomerase reverse transcriptase expression was higher in the SP, suggesting that this fraction may represent a reservoir with unlimited proliferative potential for generating cancer cells. mRNA levels of minichromosome maintenance (MCM) 7, a member of the MCM family of proteins critical to the DNA replication complex, were lower in SP cells, suggesting that a majority of the SP fraction was in the G(0) quiescent state. Sixteen clinical lung cancer samples also displayed a smaller but persistent SP population. These findings indicate that SP is an enriched source of lung tumor-initiating cells with stem cell properties and may be an important target for effective therapy and a useful tool to investigate the tumorigenic process.
干细胞已通过其外排Hoechst 33342染料的能力被分离出来，并被称为“侧群”（SP）。在本研究中，我们使用流式细胞术和Hoechst 33342染料外排试验从六种人肺癌细胞系（H460、H23、HTB - 58、A549、H441和H2170）中分离并鉴定SP细胞。非肥胖糖尿病/严重联合免疫缺陷异种移植实验表明，与非SP细胞相比，SP细胞在肿瘤起始能力方面更为富集。基质胶侵袭试验表明，SP细胞也具有更高的侵袭潜力。对这种SP表型的进一步鉴定揭示了几种干细胞特性。我们发现有证据表明SP具有重新填充能力，能够再生出类似于原始群体的群体。SP显示出ABCG2以及其他ATP结合盒转运蛋白的表达升高，并对多种化疗药物具有抗性。人端粒酶逆转录酶在SP中的表达更高，这表明该部分可能代表一个具有无限增殖潜力以产生癌细胞的储存库。微小染色体维持（MCM）7是对DNA复制复合体至关重要的MCM蛋白家族的成员，其mRNA水平在SP细胞中较低，这表明大多数SP部分处于G(0)静止状态。16个临床肺癌样本也显示出较小但持续存在的SP群体。这些发现表明，SP是具有干细胞特性的肺肿瘤起始细胞的富集来源，可能是有效治疗的重要靶点以及研究肿瘤发生过程的有用工具。
