Cancer cell heterogeneity and plasticity: A paradigm shift in glioblastoma

Phenotypic plasticity has emerged as a major contributor to intra-tumoral heterogeneity and treatment resistance in cancer. Increasing evidence shows that glioblastoma (GBM) cells display prominent intrinsic plasticity and reversibly adapt to dynamic microenvironmental conditions. Limited genetic evolution at recurrence further suggests that resistance mechanisms also largely operate at the phenotypic level. Here we review recent literature underpinning the role of GBM plasticity in creating gradients of heterogeneous cells including those that carry cancer stem cell (CSC) properties. A historical perspective from the hierarchical to the nonhierarchical concept of CSCs towards the recent appreciation of GBM plasticity is provided. Cellular states interact dynamically with each other and with the surrounding brain to shape a flexible tumor ecosystem, which enables swift adaptation to external pressure including treatment. We present the key components regulating intra-tumoral phenotypic heterogeneity and the equilibrium of phenotypic states, including genetic, epigenetic, and microenvironmental factors. We further discuss plasticity in the context of intrinsic tumor resistance, where a variable balance between preexisting resistant cells and adaptive persisters leads to reversible adaptation upon treatment. Innovative efforts targeting regulators of plasticity and mechanisms of state transitions towards treatment-resistant states are needed to restrict the adaptive capacities of GBM.     

Cell cycle heterogeneity and plasticity of colorectal cancer stem cells

Cancer stem cells (CSCs) are a long-lived and self-renewing cancer cell population that drives tumor propagation and maintains cancer heterogeneity. They are also implicated in the therapeutic resistance of various types of cancer. Recent studies of CSCs in colorectal cancer (CRC) have uncovered fundamental paradigms that have increased understanding of CSC systems in solid tumors. Colorectal CSCs share multiple biological properties with normal intestinal stem cells (ISCs), including expression of the stem cell marker Lgr5. New evidence suggests that colorectal CSCs manifest substantial heterogeneity, as exemplified by the existence of both actively cycling Lgr5⁺ CSCs as well as quiescent Lgr5⁺ CSCs that are resistant to conventional anticancer therapies. The classical view of a rigid cell hierarchy and irreversible cell differentiation trajectory in normal and neoplastic tissues is now challenged by the finding that differentiated cells have the capacity to revert to stem cells through dynamic physiological reprogramming events. Such plasticity of CSC systems likely underlies both carcinogenesis and therapeutic resistance in CRC. Further characterization of the mechanisms underpinning the heterogeneity and plasticity of CSCs should inform future development of eradicative therapeutic strategies for CRC.     

MCF-7异质性及肿瘤干细胞相关亚群初步研究

目的:探讨人乳腺癌细胞系MCF-7的异质性及其肿瘤干细胞相关亚群(SP细胞或CD44+CD24-/low细胞)的性质。方法:采用Percoll不连续密度梯度法分离MCF-7,流式细胞仪检测各亚群中SP和CD44+CD24-/low细胞比例及各亚群细胞周期时相分布,各亚群细胞体外培养获得其生长曲线,平板克隆实验检测各亚群的增殖能力。结果:经Percoll分选MCF-7可形成A、B、C、D和E 5个亚群。各亚群中SP细胞比例分别为1.43%、2.15%、6.43%、25.23%和2.09%,其中D亚群中SP细胞富集。细胞周期时相分布显示,D亚群中G0/G1静止期细胞比例最高(P<0.05),为80.58%。生长曲线显示D亚群生长速度最快,以下依次为A亚群、B亚群、C亚群和E亚群。各亚群克隆形成率分别为(32.5±3.7)%、(41.3±4.8)%、(50.8±4.3)%和(68.2±3.5)%,其中D亚群具有最高的克隆形成率(P<0.05),而E亚群未形成明显的克隆性集落。但各亚群中均未检测到明显的CD44+CD24-/low细胞。结论:乳腺癌细胞系MCF-7具有异质性特征,经Percoll分选MCF-7可形成5个异质性的亚群,其中D亚群富含肿瘤干细胞相关亚群(SP细胞),但MCF-7在长期体外培养过程中,乳腺癌干细胞表面标志CD44+CD24-/low可能已经改变。     

Lung cancer stem cells: Tumor biology and clinical implications

The concept of cancer stem cells (CSC) has drawn great attention from researchers in both molecular and clinical fields as has brought a new perspective to the way we manage cancer. CSC have several characteristics that are shared by the properties of normal stem cells, such as differentiation, self-renewal and homeostatic control. However, CSC have the capacity to both divide and expand the CSC pool and to differentiate into heterogeneous non-tumorigenic cancer cells. Even more, CSC have an inherent high resistance to chemotherapeutic agents that leads to recurrence and poor long-term survival, especially in lung cancer patients. CSC-targeting agents are now undergoing in vitro and in vivo studies, some of which have provided promising results for further clinical studies setting. In this article we review the concept of CSC from the perspective of tumor biology, including the origin of CSC and its biomarkers. As lung cancer is the leading cause of cancer-related deaths worldwide, we focus on the properties and clinical implications of lung CSC.     

Understanding the cancer stem cell

The last 15 years has seen an explosion of interest in the cancer stem cell (CSC). Although it was initially believed that only a rare population of stem cells are able to undergo self-renewing divisions and differentiate to form all populations within a malignancy, a recent work has shown that these cells may not be as rare as thought first, at least in some malignancies. Improved experimental models are beginning to uncover a less rigid structure to CSC biology, in which the concepts of functional plasticity and clonal evolution must be incorporated into the traditional models. Slowly the genetic programmes and biological processes underlying stem cell biology are being elucidated, opening the door to the development of drugs targeting the CSC. The aim of ongoing research to understand CSCs is to develop novel stem cell-directed treatments, which will reduce therapy resistance, relapse and the toxicity associated with current, non-selective agents.     

Ascites modulates cancer cell behavior,contributing to tumor heterogeneity in ovarian cancer

Malignant ascites constitute a unique tumor microenvironment providing a physical structure for the accumulation of cellular and acellular components. Ascites is initiated and maintained by physical and biological factors resulting from underlying disease and forms an ecosystem that contributes to disease progression. It has been demonstrated that the cellular contents and the molecular signatures of ascites change continuously during the course of a disease. Over the past decade, increasing attention has been given to the characterization of components of ascites and their role in the progression of ovarian cancer, the most malignant gynecologic cancer in women. This review will discuss the role of ascites in disease progression, in terms of modulating cancer cell behavior and contributing to tumor heterogeneity.     

胃癌细胞中CD44阳性细胞具有肿瘤干细胞特征

目的:在原位移植瘤模型上验证CD44+胃癌细胞的肿瘤干细胞特性.方法:选取MKN-45胃癌细胞株,通过流式细胞仪分选为CD44+和CD44-两组,以未分选的MKN-45胃癌细胞为对照.体外部分,通过MTT法和克隆形成实验验证CD44+胃癌细胞体外增殖能力,通过Transwell实验验证其侵袭力.体内部分,将上述细胞通过原位移植法接种至裸鼠,同等条件下饲养8周后处死裸鼠,检验其成瘤率;分离肝脏,检测肝转移瘤数目;H-E染色观察胃肿瘤和肝转移瘤形态;通过免疫荧光法检测两处肿瘤CD44+细胞数量.结果:CD44+胃癌细胞相比CD44‘胃癌细胞具有明显增强的细胞增殖力(P＜0.01)和侵袭力(P＜0.01),更容易成瘤且更容易发生转移(P＜0.05),但和MKN-45未分选组相比差异无统计学意义(P＞0.05).不论是在原发肿瘤还是转移瘤中,CD44+胃癌细胞均能产生CD44‘细胞,但后者不能产生CD44+细胞.结论:CD44+ MKN-45胃癌细胞相比CD44-胃癌细胞具备更强的增殖力和侵袭力、更容易成瘤和发生转移,符合肿瘤干细胞部分特征,值得进一步研究.     

靶向肿瘤干细胞治疗肿瘤

具有独特的分子表达、表面标志物、干性相关信号通路和代谢模式等方面特征的肿瘤干细胞(cancer stem cell,CSC)因其具有高致瘤、高转移、高治疗抵抗能力,可能是多种类型恶性肿瘤生长、转移、治疗抵抗的关键因素,也是肿瘤发生和复发的重要根源.正常干细胞在产生了第一个致癌突变之后将逐步发展成为癌前干细胞和CSC,随...     

Tumor stem cells

Stem cells possess two basic characteristics: they are able to renew themselves and to develop into different cell types. The link between normal stem cells and tumor cells could be examined in three aspects: what are the differences and similarities in the control of self-renewal capacity between stem cells and tumor cells; whether tumor cells arise from stem cells; do tumorous stem cells exist? Since tumor cells also exhibit self-renewal capacity, it seems plausible that their regulation is similar to that of the stem cells. The infinite self-renewal ability (immortalization) is assured by several, so far only partly known, mechanisms. One of these is telomerase activity, another important regulatory step for survival is the inhibition of apoptosis. Other signal transduction pathways in stem cell regulation may also play certain roles in carcinogenesis: e.g. Notch, Sonic hedgehog (SHH), and Wnt signals. Existence of tumor stem cells was suggested since it is simpler to retain the self-renewal capacity than to reactivate the immortality program in an already differentiated cell. Moreover, stem cells live much longer than the differentiated ones, and so they are exposed for a long period of time to impairments, collecting gene errors leading to the breakdown of the regulation. However, it is still an open question whether all cells in the tumor possess the capacity that produces this tissue or not, that is: are there tumor stem cells or there are not. If tumor stem cells exist, they would be the main target for therapy: only these must be killed since the other tumor cells possess limited proliferative capacity, therefore limited life span. The only problem is that during tumor progression stem-like cells can develop continuously and the identification but mainly the prevention of their formation is still a great challenge.(Pathology Oncology Research Vol 10, No 2, 69–73)     

肿瘤治疗的新靶标:肿瘤干细胞

近年来研究显示,在一些肿瘤中存在一些能够自我更新和分化增殖的干细胞即肿瘤干细胞。本文重点介绍了关于肿瘤干细胞的理论,研究现状,研究方法以及问题,推测肿瘤干细胞的深入研究将会对今后肿瘤防治产生巨大影响。     

以肿瘤干细胞为靶的免疫治疗

肿瘤干细胞(cancer stem cell,CSC)是肿瘤发生和转移的种子细胞,CSC具有自我更新、增殖和不完全分化的能力。CSC对化疗/放疗的抵抗以及免疫逃逸成为肿瘤复发的根源,要提高肿瘤治愈率必须彻底清除CSC。认识CSC的标记特征和"干性"调节关键分子才能有效和特异地攻击CSC。免疫治疗具有抗原识别的靶向性和时空效应性,是以CSC为靶的治疗的基础;以单克隆抗体和致敏的免疫细胞为主要治疗技术的免疫治疗清除CSC具有可实践性和挑战性。     

Brain tumor stem cells: The cancer stem cell hypothesis writ large

Brain tumors, which are typically very heterogeneous at the cellular level, appear to have a stem cell foundation. Recently, investigations from multiple groups have found that human as well as experimental mouse brain tumors contain subpopulations of cells that functionally behave as tumor stem cells, driving tumor growth and generating tumor cell progeny that form the tumor bulk, but which then lose tumorigenic ability. In human glioblastomas, these tumor stem cells express neural precursor markers and are capable of differentiating into tumor cells that express more mature neural lineage markers. In addition, modeling brain tumors in mice suggests that neural precursor cells more readily give rise to full blown tumors, narrowing potential cells of origin to those rarer brain cells that have a proliferative potential. Applying stem cell concepts and methodologies is giving fresh insight into brain tumor biology, cell of origin and mechanisms of growth, and is offering new opportunities for development of more effective treatments. The field of brain tumor stem cells remains very young and there is much to be learned before these new insights are translated into new patient treatments.     

The clinical and therapeutic implications of cancer stem cell biology

Cancer stem cells (CSCs) have provided new insights into the tumorigenesis and metastatic potential of cancer. The discovery of CSCs has provided many new insights into the complexities of cancer therapy: tumor initiation, treatment resistance, metastasis, recurrence, assessment of prognosis and prediction of clinical course. Recent rapid advances in molecular analysis have contributed to the better understanding of the molecular attributes and pathways that give CSCs their unique attributes. Use of these molecular techniques has facilitated elucidation of specific surface markers and pathways that favor propagation of CSCs – allowing for targeted therapy. Furthermore, it has been discovered that a specific microenvironment, or niche, is essential for the genesis of tumors from CSCs. Therapeutic strategies that alter these microenvironments compromise CSC proliferation and constitute another method of targeted cancer therapy. We review the clinical and therapeutic implications of CSCs, with a focus on treatment resistance and metastasis, and the emerging approaches to target CSCs and their microenvironments in order to attain improved outcomes in cancer. It is noteworthy that CSCs are the only cells capable of sustaining tumorigenesis; however, the cell of origin of cancer, in which tumorigenesis is initiated, may be distinct from CSCs that propagate the tumor.     

The side population of ovarian cancer cells defines a heterogeneous compartment exhibiting stem cell characteristics

Cancer stem cells (CSC) are believed to be involved in tumor evasion of classical antitumor therapies and have thus become an attractive target for further improvement of anticancer strategies. However, the existence and identity of CSC are still a matter of controversy. In a systematic screen of 13 ovarian cancer cell lines we show that cells with stem cell properties are reliably detectable as a minor population, characterized by ABC transporter expression resulting in the side population (SP) phenotype. In different cell lines, either ABCG2 or ABCB1 was found to be responsible for this effect. Purified SP cells featured virtually all characteristics of bona fide CSC, including clonogenicity, asymmetric division and high tumorigenicity in vivo. Using in-depth phenotyping by multicolor flow cytometry, we found that among the investigated ovarian cancer cell lines the SP compartment exhibits tremendous heterogeneity and is composed of multiple phenotypically distinct subpopulations. Thus, our study confirms previous results showing that CSC are contained within the SP. However, the exact identity of the CSC is still disguised by the high complexity of the CSC-containing compartment. Further functional studies are needed to determine whether a single cellular subset can unambiguously be defined as CSC or whether multiple stem cell-like cells with different properties coexist. Moreover, the observed heterogeneity may reflect a high level of plasticity and likely influences tumor progression, escape from immune-surveillance and development of resistance to anticancer therapies and should therefore be considered in the development of new treatment strategies.     

Cancer stem cell-immune cell collusion in immunotherapy

Immunotherapy has pioneered a new era of tumor treatment, in which the immune checkpoint blockade (ICB) exerts significant superiority in overcoming tumor immune escape. However, the formation of an immune-suppressive tumor microenvironment (TME) and the lack of effective activation of the immune response have become major obstacles limiting its development. Emerging reports indicate that cancer stem cells (CSCs) potentially play important roles in treatment resistance and progressive relapse, while current research is usually focused on CSCs themselves. In this review, we mainly emphasize the collusions between CSCs and tumor-infiltrating immune cells. We focus on the summary of CSC-immune cell crosstalk signaling pathways in ICB resistance and highlight the application of targeted drugs to improve the ICB response.     

微球体培养富集肿瘤干细胞及其潜在的临床应用

肿瘤干细胞假说是近年来提出的关于肿瘤的新理论,该理论认为肿瘤干细胞在肿瘤发生、发展和转移等过程中起着决定性的作用,肿瘤干细胞理论的提出给肿瘤治疗提供了新的思路和策略。但是,肿瘤中只有一小部分细胞为肿瘤干细胞,因此鉴定并富集这些细胞以进一步研究是众多科研人员面临的巨大挑战。微球体培养技术是近年发展起来的一种有效富集肿瘤干细胞的技术,该技术的应用使肿瘤干细胞的研究变得更加容易,并使临床应用这些细胞来评价肿瘤进展及患者预后成为可能,本文将对该技术及其与微系统的整合进行详细的阐述。      

人结肠癌CCL187细胞肿瘤球细胞干细胞特性研究

目的：研究体外培养条件下人结肠癌CCL187细胞系肿瘤球细胞的干细胞特性。方法：用无血清培养液和低吸附6孔培养板培养CCL187细胞,显微镜观察肿瘤球形成,荧光染料Hoechst33342染色观察干样细胞,用24孔培养板接种绘制CCL187细胞和肿瘤球细胞的生长曲线,顺铂和依托泊苷处理检测两种细胞抵抗化疗的能力。结果：CCL187细胞在无血清培养条件下可形成肿瘤球,肿瘤球细胞中存在浅染的干样细胞。两种细胞的生长曲线显示肿瘤球细胞的自我繁殖能力大于CCL187细胞。化疗药物处理显示肿瘤球细胞比一般肿瘤细胞具有更强的化疗抵抗性。结论：CCL187细胞的肿瘤球细胞具有肿瘤干细胞特性。     

乳腺癌异质性的研究进展及临床意义

异质性是乳腺癌的重要特征之一。尽管多数研究认为乳腺癌为单克隆起源,但由于发生、发展过程中多次分裂增殖、不断进化,表观遗传、基因组学及微环境改变导致细胞具有不同表型及生物学特征,从而产生异质性,表现为不同的组织学类型、分化程度、细胞增殖速率、侵袭转移能力及治疗反应性等诸多方面。乳腺癌个体化医疗的精准实施要求考虑到不同分子亚型以及同一个肿瘤组织内不同细胞亚群的存在。就乳腺癌异质性的起源、分类、表型特点及临床意义等研究进展进行综述。