Respirology：肺癌干细胞存在的根据和争论

肿瘤干细胞的存在与否，一直是近年来学术界争论不休的问题，针对这一问题，来自澳大利亚莫纳什医疗中心肿瘤科的Muhammad Alamgeer回顾了相关文献，针对一些有争议的问题进行了讨论。该文献发表2013年4月16日的呼吸系统疾病（Respirology）杂志上，该文章回顾总结了近年来一些关于癌症干细胞的实验及临床研究，探讨了一些相关问题，并提出了一些设想。
癌症干细胞理论是基于大量实验和临床观察的基础上提出的，这些实验和临床观察显示少数具有自我复制、分化及先天对放化疗耐受的细胞可以导致恶性表型的持续存在。癌症干细胞有可能是最终治疗后癌症复发的原因，其在功能上等同于微小病灶。与其他实体肿瘤类似，一些公认的肺癌干细胞表面标志物已经被鉴定出来，其中包括CD133和CD44。另外，细胞质中乙醛脱氢酶的高表达、细胞膜渗透性染料排除能力（被称为“侧群”）和癌症干细胞在体内和体外的关系也已经明确。胚胎干细胞途径如Hedgehog信号途径、Notch信号途径、Wnt信号途径在肺癌干细胞中也可能处于高表达状态。这些研究的目标是为手术后或者放化疗后完全缓解后的患者提供长期维持治疗。
癌症干细胞理论是非常重要的肿瘤生物学理论模型，很好的解释了一些先天性耐药的癌症细胞，并对癌症患者长期维持治疗提出了美好的设想，癌症干细胞到目前为止没有发现有足够特异性的标志物，其存在的证据仍然不足。但是一些相关研究为未来的肿瘤治疗提供了新的治疗策略和方法。

Cancer Stem Cells in Lung Cancer: Evidence and Controversies.
Abstract
The cancer stem cell model is based on a myriad of experimental and clinical observations suggesting that the malignant phenotype is sustained by a subset of cells characterized by the capacity for self-renewal, differentiation and innate resistance to chemotherapy and radiation. Cancer stem cells may be responsible for disease recurrence after definitive therapy and may therefore be functionally synonymous with minimal residual disease. Similar to other solid tumours, several putative surface markers for lung cancer stem cells have been identified, including CD133 and CD44. In addition, expression and/or activity of the cytoplasmic enzyme ALDH, and capacity of cells to exclude membrane permeable dyes (known as the "side population") correlate with stem-like function in vitro and in vivo. Embryonic stem cell pathways such as Hedgehog, Notch and WNT may also be active in lung cancers stem cells, and therefore may be therapeutically targetable for maintenance therapy in patients achieving a complete response to surgery, radiotherapy or chemotherapy. This paper will review the evidence regarding the existence and function of lung cancer stem cells in the context of the experimental and clinical evidence and discuss some ongoing controversies regarding this model.