肿瘤干细胞生物学特性及其干性维持机制的研究进展

肿瘤是威胁人类健康和社会发展最为严重的疾病之一,也是全球第二大常见疾病死因。最新统计数据显示,恶性肿瘤在发达国家已取代心血管疾病成为第一大疾病死因。肿瘤的耐药、转移和复发,仍然是临床治疗中亟需解决的难题。肿瘤干细胞(tumor stem cells, TSCs)是一类具有自我更新、分化潜能、高致瘤性和高耐药性等特征的细胞亚群,能够抵抗放化疗等非特异性治疗手段,在肿瘤发生、转移、耐药和复发中发挥关键作用。肿瘤干细胞标志物、干性维持机制、微环境和代谢重编程等领域已成为了研究热点,最新研究成果为肿瘤干细胞的鉴定和靶向治疗提供了新的靶标和策略。本文对肿瘤干细胞的表面标志物(CD133和CD44等)、自我更新和上皮细胞间充质转化(epithelial mesenchymal transition, EMT)信号通路(Wnt/β-catenin和Hedgehog等)、微环境特征、代谢重编程(糖酵解和氧化磷酸化等),及其在肿瘤的起始、发展、转移和耐药中的作用进行了综述。     

肿瘤干细胞的研究进展

肿瘤干细胞(cancer/tumor stem cell,CSC/TSC)假说认为肿瘤组织中存在极少量的瘤细胞充当着干细胞的角色,它们具有自我更新能力、无限增殖能力,且能驱动肿瘤的形成和生长。近年来,随着在血液肿瘤和实体瘤中相继发现CSC/TSC存在的相关证据,对CSC/TSC的生物学特性的认识不断深入,对肿瘤的复发、转移、耐药性等特点也有了新的观点和研究方向,就近年来该方面的进展作一综述。     

肿瘤干细胞研究进展

目前,癌症是导致人类死亡的主要因素之一。尽管在癌症治疗方面取得了巨大进展,但是,其较高的复发率还是会导致死亡。连续治疗失败的一个可能原因是,残留的恶性细胞有类似干细胞的分化潜能,这样就能再次形成肿瘤和造成病灶转移。肿瘤干细胞(cancer stem cell,CSC)假说认为,肿瘤组织中存在具有自我跟新能力,无限增殖和肿瘤形成能力的一小部分肿瘤细胞,近年来,随着在血液肿瘤和实体瘤中相继发现CSC存在的相关证据,对CSC的生物学特性的认识不断深入,对肿瘤的复发、病灶转移、耐药性形成也有了新的观点和研究方向,目前的研究主要集中在其分离鉴定阶段,本文就近年来该方面的研究进展作一综述。     

肿瘤干细胞起源及其生物学特性

肿瘤干细胞与正常成体干细胞在自我更新与增殖分化能力、表型标记和强耐药性等诸多方面存在着相类似的生物学特征,所以肿瘤干细胞被推测为肿瘤发生的细胞起源。基于肿瘤干细胞与正常干细胞之间的相似性质和肿瘤发生的分子机制,科学家建立了一系列从肿瘤组织或肿瘤细胞系分离肿瘤干细胞的实验方法和研究肿瘤干细胞起源的动物实验模型。现就目前在肿瘤干细胞起源和生物学特性领域的研究作概括阐述。     

肿瘤干细胞鉴定方法

肿瘤干细胞假说是近年来提出的关于肿瘤发生的新理论,该理论认为肿瘤组织中仅有一小部分细胞可以产生肿瘤并且维持肿瘤生长。在体内外如何鉴定这种具有启动以及保持肿瘤生长的细胞类型,成为肿瘤基础及应用研究的关键问题。目前已经在白血病、乳腺癌、神经胶质瘤等肿瘤中成功鉴定并分离出肿瘤干细胞,这对于肿瘤的临床治疗具有重要意义。本文主要从肿瘤干细胞的鉴定及其在临床研究中的应用等方面进行综述。     

白血病干细胞的生物学特性

白血病干细胞是第一个被确认的肿瘤干细胞,在白血病的形成和病情的发展中具有重要作用。深入研究其生物学特性将为白血病的发病机制以及干细胞靶向治疗奠定理论基础。该文介绍白血病干细胞的免疫表型、自我更新机制、生存优势及多重耐药等。     

微小RNA与肿瘤干细胞耐药的研究进展

肿瘤干细胞（Cancer stem cells,CSCs）是肿瘤组织中一小部分具有自我更新和致瘤性的细胞,具有特殊的耐药机制,与肿瘤的复发和治疗失败关系密切。微小RNA（microRNAs,miRNAs）是一类长度约为19～25个核苷酸的内源性非编码单链RNA,能够通过调控相关靶基因的表达,参与调控肿瘤干细胞增殖、凋亡、上皮-间质转化等重要的生命过程,引起CSCs对化疗药物产生原发性多药耐药性。本论文就miRNAs在调控CSCs多药耐药性方面的研究进展作一综述。     

人神经干细胞的体外生物学特性

本实验利用有丝分裂因子,体外诱导生成人神 经干细胞(NSCs),观察其生长特性并进行鉴定。取胎龄10-22周的大脑半球,分散细胞后种于添加表皮生长因子(EGF,20ng/ml)和/或碱性成纤维生长因子(bFGF,20ng/ml)的培养基中。利用免疫组织化学方法鉴定分化后的细胞类型。同时,进行细胞克隆分析、传代培养及端粒酶活性检测。结果显示:NSCs呈悬浮生长的干细胞球,其特异性抗原nestin阳性。NSCs具有增殖能力,可连续传代而不丢失其增殖和多分化潜能的干细胞特性。撤除EGF和bFGF的作用,细胞停止分裂,并分化为神经元、星形胶质细胞和少突胶质细胞。克隆分析显示NSCs生长呈密度依赖性。人NSCs表达较低的端粒酶水平,并随培养时间延长而下调。研究表明,利用有丝分裂因子,可在体外成功诱导生成人NSCs,其生长,分化受内外源因素的调节,相关的机制还有待阐明。     

间充质干细胞与肿瘤形成的研究进展

间充质干细胞(Mesenchymal stem cells,MSCs)具有独特的免疫调节作用、自我更新和跨胚层多向分化的潜能,存在于许多组织中并活跃地向组织损伤部位迁移,参与伤口修复。在对肿瘤的信号发生反应后,MSCs不断被招募并成为肿瘤微环境的成分。肿瘤相关MSCs(Tumor-associated MSCs, TA-MSCs)在肿瘤发生、促进、进展和转移中有重要作用。本文对MSCs在调节肿瘤细胞的存活、增殖、迁移、药物抵抗中如何发挥作用,以及MSCs对肿瘤微环境免疫状态的影响作一综述。我们强调了MSCs和其他肿瘤基质细胞之间的复杂关系,特别是炎症细胞可以改变肿瘤微环境的免疫状态,以期通过对TA-MSCs进一步的研究来取得对不同肿瘤类型和肿瘤进展不同阶段中肿瘤相关MSCs功能的更好的理解,并优化MSCs来得到更有效和安全的MSCs为基础的肿瘤治疗。MSCs已被有效用于治疗慢性炎性疾病和慢性损伤,因此,其机制方面的研究还有利于在其他疾病中合理利用MSCs从而达到疾病治疗的目的。     

基于肿瘤干细胞的恶性肿瘤靶向治疗策略

肿瘤干细胞与肿瘤的形成、进展及转移息息相关。针对肿瘤干细胞的靶向治疗已成为控制并治愈恶性肿瘤的新方法。该文就肿瘤干细胞及基于肿瘤干细胞靶向治疗恶性肿瘤的策略,如针对其表面标志物、信号传导通路、诱导分化、干预微环境、免疫疗法等加以综述,为进一步开展针对肿瘤干细胞的靶向疗法提供参考。     

癌干细胞研究进展

关于肿瘤发生及发展的机制人们已探索多年,但由于肿瘤病因本身的复杂性、研究技术和知识积累不足等各种原因,研究进展缓慢。近些年来,癌干细胞的发现、确认和特性研究为肿瘤发病机制的揭示,乃至新型高效治疗策略的制定提出了新线索。许多研究成果显示,癌干细胞因具有自我更新和潜在的强增殖能力,在肿瘤发生发展、复发转移中均发挥着很重要的作用;肿瘤化疗的失败与肿瘤组织中癌干细胞的耐药性可能存在密切关系。本文就癌干细胞在这方面的研究进展及存在的问题作一综述。     

肿瘤干细胞研究进展

在过去的十年中,肿瘤干细胞（cancer stem cell／tumor—initiating cell,CSC／TIC）虽然受到广泛重视,但也是争论的焦点。如何正确认识CSCs假说,以及CSCs的生物学特点和CSCs的治疗应用这些问题都存在巨大的争议。该文对CSCS的起源、分离鉴定的方法,以及信号通路、微环境等对cSCS的调控关系,肿瘤的最佳治疗途径等问题进行综述。     

Prospects for the involvement of cancer stem cells in the pathogenesis of osteosarcoma

Osteosarcoma (OS) is one of the most common bone tumors in children and adolescents that cause a high rate of mortality in this age group and tends to be metastatic, in spite of chemotherapy and surgery. The main reason for this can be returned to a small group of malignant cells called cancer stem cells (CSCs). OS-CSCs play a key role in the resistance to treatment and relapse and metastasis through self-renewal and differentiation abilities. In this review, we intend to go through the different aspects of this malignant disease, including the cancer stem cell-phenotype, methods for isolating CSCs, signaling pathways, and molecular markers in this disease, and drugs showing resistance in treatment efforts of OS.     

肿瘤干细胞与肿瘤转移

近年来,肿瘤干细胞(cancer stem cell,CSC)学说研究认为CSC与肿瘤发生、发展、转移和复发关系极为密切。研究还发现CSC具有明显的异质性,即CSC可分为增生、耐药、侵袭和转移等行为不同的亚群细胞,其中具有转移生物学特性的CSC亚群细胞称为肿瘤转移干细胞(migrating cancer stem cell,MCSC)。目前认为,上皮-间质转变、趋化因子和靶器官微环境可能在肿瘤转移过程中起着重要作用。针对MCSC及其相关机制的靶向治疗有望能更有效地遏制肿瘤的转移。     

肿瘤干细胞与血管新生的研究进展

肿瘤生长及转移依赖于新生血管的形成,大量研究认为肿瘤干细胞与血管新生之间存在密切联系,肿瘤干细胞可能转分化为内皮细胞参与新生血管生成,并通过分泌促血管生长因子、基质衍生因子和低氧诱导因子参与对血管新生的调控。     

Therapy targets in glioblastoma and cancer stem cells: lessons from haematopoietic neoplasms

Despite intense efforts to identify cancer‐initiating cells in malignant brain tumours, markers linked to the function of these cells have only very recently begun to be uncovered. The notion of cancer stem cell gained prominence, several molecules and signalling pathways becoming relevant for diagnosis and treatment. Whether a substantial fraction or only a tiny minority of cells in a tumor can initiate and perpetuate cancer, is still debated. The paradigm of cancer‐initiating stem cells has initially been developed with respect to blood cancers where chronic conditions such as myeloproliferative neoplasms are due to mutations acquired in a haematopoietic stem cell (HSC), which maintains the normal hierarchy to neoplastic haematopoiesis. In contrast, acute leukaemia transformation of such blood neoplasms appears to derive not only from HSCs but also from committed progenitors that cannot differentiate. This review will focus on putative novel therapy targets represented by markers described to define cancer stem/initiating cells in malignant gliomas, which have been called ‘leukaemia of the brain’, given their rapid migration and evolution. Parallels are drawn with other cancers, especially haematopoietic, given the similar rampant proliferation and treatment resistance of glioblastoma multiforme and secondary acute leukaemias. Genes associated with the malignant conditions and especially expressed in glioma cancer stem cells are intensively searched. Although many such molecules might only coincidentally be expressed in cancer‐initiating cells, some may function in the oncogenic process, and those would be the prime candidates for diagnostic and targeted therapy. For the latter, combination therapies are likely to be envisaged, given the robust and plastic signalling networks supporting malignant proliferation.     

Tissue-specific cancer stem/progenitor cells: Therapeutic implications

Surgical resection, chemotherapy, and radiation are the standard therapeutic modalities for treating cancer. These approaches are intended to target the more mature and rapidly dividing cancer cells. However, they spare the relatively quiescent and intrinsically resistant cancer stem cells (CSCs) subpopulation residing within the tumor tissue. Thus, a temporary eradication is achieved and the tumor bulk tends to revert supported by CSCs' resistant features. Based on their unique expression profile, the identification, isolation, and selective targeting of CSCs hold great promise for challenging treatment failure and reducing the risk of cancer recurrence. Yet, targeting CSCs is limited mainly by the irrelevance of the utilized cancer models. A new era of targeted and personalized anti-cancer therapies has been developed with cancer patient-derived organoids (PDOs) as a tool for establishing pre-clinical tumor models. Herein, we discuss the updated and presently available tissue-specific CSC markers in five highly occurring solid tumors. Additionally, we highlight the advantage and relevance of the three-dimensional PDOs culture model as a platform for modeling cancer, evaluating the efficacy of CSC-based therapeutics, and predicting drug response in cancer patients.     

Differential effect of long-term drug selection with doxorubicin and vorinostat on neuroblastoma cells with cancer stem cell characteristics

Numerous studies have confirmed that cancer stem cells (CSCs) are more resistant to chemotherapy; however, there is a paucity of data exploring the effect of long-term drug treatment on the CSC sub-population. The purpose of this study was to investigate whether long-term doxorubicin treatment could expand the neuroblastoma cells with CSC characteristics and histone acetylation could affect stemness gene expression during the development of drug resistance. Using n-myc amplified SK-N-Be(2)C and non-n-myc amplified SK-N-SH human neuroblastoma cells, our laboratory generated doxorubicin-resistant cell lines in parallel over 1 year; one cell line intermittently treated with the histone deacetylase inhibitor (HDACi) vorinostat and the other without exposure to HDACi. Cells'' sensitivity to chemotherapeutic drugs, the ability to form tumorspheres, and capacity for in vitro invasion were examined. Cell-surface markers and side populations (SPs) were analyzed using flow cytometry. Differentially expressed stemness genes were identified through whole genome analysis and confirmed with real-time PCR. Our results indicated that vorinostat increased the sensitivity of only SK-N-Be(2)C-resistant cells to chemotherapy, made cells lose the ability to form tumorspheres, and reduced in vitro invasion and the SP percentage. CD133 was not enriched in doxorubicin-resistant or vorinostat-treated doxorubicin-resistant cells. Nine stemness-linked genes (ABCB1, ABCC4, LMO2, SOX2, ERCC5, S100A10, IGFBP3, TCF3, and VIM) were downregulated in vorinostat-treated doxorubicin-resistant SK-N-Be(2)C cells relative to doxorubicin-resistant cells. A sub-population of cells with CSC characteristics is enriched during prolonged drug selection of n-myc amplified SK-N-Be(2)C neuroblastoma cells. Vorinostat treatment affects the reversal of drug resistance in SK-N-Be(2)C cells and may be associated with downregulation of stemness gene expression. This work may be valuable for clinicians to design treatment protocols specific for different neuroblastoma patients.