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。     

Non-coding RNAs regulate tumor cell plasticity

Tumor metastasis is one of the most serious challenges for human cancers as the majority of deaths caused by cancer are associated with metastasis, rather than the primary tumor. Recent studies have demonstrated that tumor cell plasticity plays a critical role in tumor metastasis by giving rise to various cell types which is necessary for tumor to invade adjacent tissues and form distant metastasis. These include differentiation of cancer stem cells (CSCs), or epithelial-mesenchymal transition (EMT) and its reverse process, mesenchymal-epithelial transition (MET). A growing body of evidence has demonstrated that the biology of tumor cell plasticity is tightly linked to functions of non-coding RNAs (ncRNAs), especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Therefore, understanding the mechanisms how non-coding RNAs regulate tumor cell plasticity is essential for discovery of new diagnostic markers and therapeutic targets to overcome metastasis.     

Reprogramming strategies for the establishment of novel human cancer models

Cancer comprises heterogeneous cells, ranging from highly proliferative immature precursors to more differentiated cell lineages. The emergence of the “cancer stem cell” (CSC) hypothesis that they are the cells responsible for resistance, metastasis and secondary tumor appearance identifies these populations as novel obligatory targets for the treatment of cancer. CSCs, like their normal tissue-specific stem cell counterparts, are multipotent, partially differentiated, self-sustaining, yet transformed cells. To date, most studies on CSC biology have relied on the use of murine models and primary human material. In spite of much progress, the use of primary material presents several limitations that limit our understanding of the mechanisms underlying CSC formation, the similarities between normal stem cells and CSCs and ultimately, the possibility for developing targeted therapies. Recently, different strategies for controlling cell fate have been applied to the modeling of human cancer initiation and for the generation of human CSC models. Here we will summarize recent developments in the establishment and application of reprogramming strategies for the modeling of human cancer initiation and CSC formation.     

Prostate stem cells and cancer

Properties shared by neoplastic and stem cells indicate a possibility that somatic stem cells or transit-amplifying cells that have reacquired stem cell properties, particularly the ability for self-renewal, represent favorable targets for malignant transformation. In this review we discuss significance of the stem cell model for understanding prostate cancer pathogenesis and describe relevant studies in animals. It is proposed that dissemination of rare cancer stem cells may lead to metastatic disease and that resistance of such cells to multiple drugs and androgen ablation make them responsible for failure of current treatments. Thus further understanding of the cancer stem cell biology is needed for development of efficient rationally designed therapy permitting better targeting and better treatment outcomes for patients with prostate neoplasms.     

Role of liver stem cells in hepatocarcinogenesis

Liver cancer is an aggressive disease with a high mortality rate. Management of liver cancer is strongly dependent on the tumor stage and underlying liver disease. Unfortunately, most cases are discovered when the cancer is already advanced, missing the opportunity for surgical resection. Thus, an improved understanding of the mechanisms responsible for liver cancer initiation and progression will facilitate the detection of more reliable tumor markers and the development of new small molecules for targeted therapy of liver cancer. Recently, there is increasing evidence for the “cancer stem cell hypothesis”, which postulates that liver cancer originates from the malignant transformation of liver stem/progenitor cells (liver cancer stem cells). This cancer stem cell model has important significance for understanding the basic biology of liver cancer and has profound importance for the development of new strategies for cancer prevention and treatment. In this review, we highlight recent advances in the role of liver stem cells in hepatocarcinogenesis. Our review of the literature shows that identification of the cellular origin and the signaling pathways involved is challenging issues in liver cancer with pivotal implications in therapeutic perspectives. Although the dedifferentiation of mature hepatocytes/cholangiocytes in hepatocarcinogenesis cannot be excluded, neoplastic transformation of a stem cell subpopulation more easily explains hepatocarcinogenesis. Elimination of liver cancer stem cells in liver cancer could result in the degeneration of downstream cells, which makes them potential targets for liver cancer therapies. Therefore, liver stem cells could represent a new target for therapeutic approaches to liver cancer in the near future.     

Cancer stem cells as a therapeutic target in bladder cancer

Bladder cancer is one of the most prevalent genitourinary cancers responsible for about 150,000 deaths per year worldwide. Currently, several treatments, such as endoscopic and open surgery, appended by local or systemic immunotherapy, chemotherapy, and radiotherapy are used to treat this malignancy. However, the differences in treatment outcome among patients suffering from bladder cancer are considered as one of the important challenges. In recent years, cancer stem cells, representing a population of undifferentiated cells with stem-cell like properties, have been eyed as a major culprit for the high recurrence rate in superficial papillary bladder cancer. Cancer stem cells have been reported to be resistant to conventional treatments, such as chemotherapy, radiation, and immunotherapy, which induce selective pressure on tumoral populations resulting in selection and growth of the resistant cells. Therefore, targeting the therapeutic aspects of cancer stem cells in bladder cancer may be promising. In this study, we briefly discuss the biology of bladder cancer and then address the possible relationship between molecular biology of bladder cancer and cancer stem cells. Subsequently, the mechanisms of resistance applied by cancer stem cells against the conventional therapeutic tools, especially chemotherapy, are discussed. Moreover, by emphasizing the biomarkers described for cancer stem cells in bladder cancer, we have provided, described, and proposed targets on cancer stem cells for therapeutic interventions and, finally, reviewed some immunotargeting strategies against bladder cancer stem cells.     

Brain tumour stem cells: the undercurrents of human brain cancer and their relationship to neural stem cells

Conceptual and technical advances in neural stem cell biology are being applied to the study of human brain tumours. These studies suggest that human brain tumours are organized as a hierarchy and are maintained by a small number of tumour cells that have stem cell properties. Most of the bulk population of human brain tumours comprise cells that have lost the ability to initiate and maintain tumour growth. Although the cell of origin for human brain tumours is uncertain, recent evidence points towards the brain's known proliferative zones. The identification of brain tumour stem cells has important implications for understanding brain tumour biology and these cells may be critical cellular targets for curative therapy.     

Therapeutic biology: checkpoint pathway activation therapy, HIV Tat, and transkingdom RNA interference

Therapeutic biology is an exciting new frontier in the post-genomic era with the mission to better human health. The explosive increase in the understanding of molecular and regulatory biology has enabled the identification of a plethora of potential targets and pathways for the discovery of new medicines. Conversely, molecularly based therapeutic intervention of biological aberrations in human diseases offers a test of the depth of our understanding of biology. This article discusses three examples of therapeutic biology research. The first concerns the treatment of cancer by activating genome surveillance circuitry, namely checkpoint-pathway activation therapy. The second example is the identification of the HIV Tat protein as both a cause of immune cell activation and apoptosis, and as a vaccine candidate against HIV infection. The third example describes transkingdom RNA interference and its application in the investigational and therapeutic silencing of disease genes.     

FIP200, a key signaling node to coordinately regulate various cellular processes

A central question in cell biology is how various cellular processes are coordinately regulated in normal cell and how dysregulation of the normal signaling pathways leads to diseases such as cancer. Recent studies have identified FIP200 as a crucial signaling component to coordinately regulate different cellular events by its interaction with multiple signaling pathways. This review will focus on the cellular functions of FIP200 and its interacting proteins, as well as the emerging roles of FIP200 in embryogenesis and cancer development. Further understanding of FIP200 function might provide novel therapeutic targets for human diseases such as cancer.     

Epithelial plasticity and cancer stem cells: Major mechanisms of cancer pathogenesis and therapy resistance

Epithelial-mesenchymal transition(EMT) has been linked with aggressive tumor biology and therapy resistance. It plays central role not only in the generation of cancer stem cells(CSCs) but also direct them across the multiple organ systems to promote tumor recurrence and metastasis. CSCs are reported to express stem cell genes as well as specific cell surfacemarkers and allow aberrant differentiation of progenies.It facilitates cancer cells to leave primary tumor, acquire migratory characteristics, grow into new environment and develop radio-chemo-resistance. Based on the current information, present review discusses and summarizes the recent advancements on the molecular mechanisms that derive epithelial plasticity and its major role in generating a subset of tumor cells with stemness properties and pathophysiological spread of tumor. This paper further highlights the critical need to examine the regulation of EMT and CSC pathways in identifying the novel probable therapeutic targets.These improved therapeutic strategies based on the co-administration of inhibitors of EMT, CSCs as well as differentiated tumor cells may provide improved antineoplastic response with no tumor relapse.     

综述:基于人多潜能干细胞的人类疾病研究与治疗

人多潜能干细胞(hPSC)包括人胚胎干细胞(hESC)和诱导性多潜能干细胞(hiPSC),理论上具有分化成为人类所有细胞类型的能力.基于hPSC的基因打靶技术,不但可以纠正人基因组中的遗传突变用于细胞治疗,还可以通过反向遗传学的方式向hPSC引入疾病特异的突变.将携带人类疾病遗传基因的hPSC分化为特定的细胞类型,在理论上可以在体外模拟人类疾病的发生,研究人类疾病发生的机理,并建立体外筛选平台寻找治疗性药物.基因编辑和干细胞技术的结合将为人类疾病的机制研究和再生医学治疗带来革命性的突破.     

Regulation of reactive oxygen species in stem cells and cancer stem cells

Stem cells are defined by their ability to self-renew and their multi-potent differentiation capacity. As such, stem cells maintain tissue homeostasis throughout the life of a multicellular organism. Aerobic metabolism, while enabling efficient energy production, also generates reactive oxygen species (ROS), which damage cellular components. Until recently, the focus in stem cell biology has been on the adverse effects of ROS, particularly the damaging effects of ROS accumulation on tissue aging and the development of cancer, and various anti-oxidative and anti-stress mechanisms of stem cells have been characterized. However, it has become increasingly clear that, in some cases, redox status plays an important role in stem cell maintenance, i.e., regulation of the cell cycle. An active area of current research is redox regulation in various cancer stem cells, the malignant counterparts of normal stem cells that are viewed as good targets of cancer therapy. In contrast to cancer cells, in which ROS levels are increased, some cancer stem cells maintain low ROS levels, exhibiting redox patterns that are similar to the corresponding normal stem cell. To fully elucidate the mechanisms involved in stem cell maintenance and to effectively target cancer stem cells, it is essential to understand ROS regulatory mechanisms in these different cell types. Here, the mechanisms of redox regulation in normal stem cells, cancer cells, and cancer stem cells are reviewed.     

The hypoxic microenvironment maintains glioblastoma stem cells and promotes reprogramming towards a cancer stem cell phenotype

Glioblastomas are highly lethal cancers that contain cellular hierarchies with self-renewing cancer stem cells that can propagate tumors in secondary transplant assays. The potential significance of cancer stem cells in cancer biology has been demonstrated by studies showing contributions to therapeutic resistance, angiogenesis, and tumor dispersal. We recently reported that physiologic oxygen levels differentially induce hypoxia inducible factor-2α (HIF2α) levels in cancer stem cells. HIF1α functioned in proliferation and survival of all cancer cells but also was activated in normal neural progenitors suggesting a potentially restricted therapeutic index while HIF2α was essential in only in cancer stem cells and was not expressed by normal neural progenitors demonstrating HIF2α is a cancer stem cell specific target. We now extend these studies to examine the role of hypoxia in regulating tumor cell plasticity. We find that hypoxia promotes the self-renewal capability of the stem and non-stem population as well as promoting a more stem-like phenotype in the non-stem population with increased neurosphere formation as well as upregulation of important stem cell factors, such as OCT4, NANOG, and c-MYC. The importance of HIF2α was further supported as forced expression of non-degradable HIF2α induced a cancer stem cell marker and augmented the tumorigenic potential of the non-stem population. This novel finding may indicate a specific role of HIF2α in promoting glioma tumorigenesis. The unexpected plasticity of the non-stem glioma population and the stem-like phenotype emphasizes the importance of developing therapeutic strategies targeting the microenvironmental influence on the tumor in addition to cancer stem cells.     

Roots and stems: stem cells in cancer

Cancer develops from normal tissues through the accumulation of genetic alterations that act in concert to confer malignant phenotypes. Although we have now identified some of the genes that when mutated initiate tumor formation and drive cancer progression, the identity of the cell population(s) susceptible to such transforming events remains undefined for the majority of human cancers. Recent work indicates that a small population of cells endowed with unique self-renewal properties and tumorigenic potential is present in some, and perhaps all, tumors. Although our understanding of the biology of these putative cancer stem cells remains rudimentary, the existence of such cells has implications for current conceptualizations of malignant transformation and therapeutic approaches to cancer.     

Single-cell analysis of tumors: Creating new value for molecular biomarker discovery of cancer stem cells and tumor-infiltrating immune cells

Biomarker-driven individualized treatment in oncology has made tremendous progress through technological developments, new therapeutic modalities and a deeper understanding of the molecular biology for tumors, cancer stem cells and tumor-infiltrating immune cells. Recent technical developments have led to the establishment of a variety of cancer-related diagnostic, prognostic and predictive biomarkers. In this regard, different modern OMICs approaches were assessed in order to categorize and classify prognostically different forms of neoplasia. Despite those technical advancements, the extent of molecular heterogeneity at the individual cell level in human tumors remains largely uncharacterized. Each tumor consists of a mixture of heterogeneous cell types. Therefore, it is important to quantify the dynamic cellular variations in order to predict clinical parameters, such as a response to treatment and or potential for disease recurrence. Recently, single-cell based methods have been developed to characterize the heterogeneity in seemingly homogenous cancer cell populations prior to and during treatment. In this review, we highlight the recent advances for single-cell analysis and discuss the challenges and prospects for molecular characterization of cancer cells, cancer stem cells and tumor-infiltrating immune cells.     

Breast Cancer Genes PSMC3IP and EPSTI1 Play a Role in Apoptosis Regulation

A key element to delineate the biology of individual tumors is the regulation of apoptosis. In this work, we functionally characterize two breast cancer associated genes, the proteasome 26S subunit ATPase 3 interacting protein (PSMC3IP) and the epithelial-stromal interaction 1 (EPSTI1), to explore their potential apoptotic role in breast cancer. We first explore the existence of direct physical interactions with annotated BC-apoptotic genes. Based on the generated interaction network, we examine several apoptotic markers to determine the effect of PSMC3IP and EPSTI1 gene expression modulation in two different human breast cancer cell lines to suggest potential molecular mechanisms to unveil their role in the disease. Our results show that PSMC3IP and EPSTI1 are able to modulate the extrinsic apoptotic pathway in estrogen receptor positive and triple negative breast cancer cell lines, highlighting them as potential therapeutic targets.     

Cancer stem cell markers as potential targets for epithelial cancers

In recent years, the role of tumor-initiating cells (popularly known as cancer stem cells) in tumor development and availability of novel cancer stem cell/tumor initiating cell markers promises a new arena in understanding their role in developing novel targeted molecules. It is important to identify and understand the relevance of cancer stem cells (CSC)/tumor initiating cells (TIC) in tumor development and to design appropriate strategies for CSCs and TICs elimination, which is crucial to future cancer prevention and treatment. In this review, we attempt to define various potential markers of cancer stem cells and potential exploration as therapeutic targets for epithelial cancer prevention and treatment.