MicroRNA regulation of cancer stem cells

Cancer stem cells (CSC), or cancer cells with stem cell properties, have been reported in many human tumors and are thought to be responsible for tumor initiation, therapy resistance, progression, relapse, and metastasis. Despite their potential clinical importance, how CSCs are regulated at the molecular level is not well understood. MicroRNAs (miRNA), small noncoding RNAs that play critical roles in normal stem cell functions during development, have emerged as important regulators of CSCs as well. In this review, we summarize the current major findings of miRNA regulation of various CSCs and discuss our recent findings that miR-34a suppresses prostate CSCs and metastasis by directly repressing CD44. This recent progress has important implications for understanding how CSCs are intricately regulated by networks of miRNAs and for developing novel mechanism-based miRNA therapeutics that specifically target CSCs.     

肾癌干细胞与表观遗传学调控研究进展

针对肿瘤干细胞进行靶向治疗是遏止肿瘤复发和转移的关键。表观遗传学在干细胞发育及体细胞重编程中的重要作用提示其可能在肿瘤干细胞的发生发展中发挥作用。表观基因组包含DNA甲基化、组蛋白修饰、染色体重塑和非编码RNA调控的基因表达模式,在肾癌细胞中有多种表观基因组的异常改变。目前已成功的从肾细胞癌中获得SP细胞、细胞囊球和CD105+细胞等具肿瘤干细胞属性的细胞亚群。随着对肾细胞癌（renal cell carcinoma,RCC）遗传研究的不断深入,发现DNA序列以外的调控机制异常在肿瘤的发生发展过程中起重要的作用。对肾癌发生相关的表观遗传学的认识有助于推进新的治疗方式,而对发现新的预后和早期诊断标志将起更重要的作用。本文对目前肾癌干细胞和表观遗传学相关领域的最新研究,特别是肾癌干细胞发生和发展过程中表观遗传学可能的调控作用及机制进行综述。      

Mesenchymal stem cells,cancer challenges and new directions

Therapeutic use of multipotent mesenchymal stromal stem cells (MSC) is a promising venue for a large number of degenerative diseases and cancer. Their availability from many different adult tissues, ease of expansion in culture, the ability to avoid immune rejection and their homing ability, are some of the properties of MSCs that make them a great resource for therapy. However, the challenges and risks for cell-based therapies are multifaceted. The blessing of cell culture expansion also comes with a burden. During in vitro expansion, stem cells experience a long replicative history and therefore, become subjected to damage from intracellular and extracellular influences. As previously shown cells that are manipulated to obtain an expanded replicative potential are prone to spontaneous transformation in culture. These manipulations help bypass the naturally built-in controls of the cell that govern the delicate balance between cell proliferation, senescence and carcinogenesis.Because of this, there is a risk for patients receiving stem cells that are in vitro expanded. Whether these cells are genetically engineered or harbouring xenogenic compounds, they cannot truly be considered “safe” unless the cells are closely monitored.In the present communication, we will focus on the therapeutic potential of the human mesenchymal stem cells (hMSC) with special focus on their use in cancer therapy. We will consider different mechanisms, by which stem cells can maintain telomeres and thereby the cell’s ability to be expanded in vitro, and also focus on a new therapeutic venue that utilises hMSCs as delivery vehicles in innovative new cancer treatments.     

乳腺癌干细胞及其临床应用

乳腺癌干细胞(BCSC)是乳腺癌细胞中一类具有自我更新能力和多向分化潜能的细胞.这类细胞具有高度的致瘤性和侵袭转移性,在乳腺癌的转移和复发以及放化疗抵抗中都起着重要作用.针对BCSC进行靶向治疗对提高乳腺癌疗效具有重要意义.     

MicroRNA在肿瘤干细胞中的调控作用研究进展

肿瘤干细胞(CSCs)是导致肿瘤复发、转移和耐药的根源之一。microRNA(miRNAs)是一类小分子非编码RNA,可与靶mRNA的3’UTR区域结合而导致该mRNA分子的翻译受到抑制,参与多种生物功能的调节。最近的研究发现,miRNAs参与CSCs的分化、自我更新等生物学特性的调控。miRNAs可以作为CSCs研究的一个新的切入点。本文就近年来该方面的研究进展做简要综述。     

MicroRNA在肿瘤干细胞中的调控作用研究进展

肿瘤干细胞（CSCs）是导致肿瘤复发、转移和耐药的根源之一。microRNA（miRNAs）是一类小分子非编码RNA,可与靶mRNA的3＇UTR区域结合而导致该mRNA分子的翻译受到抑制,参与多种生物功能的调节。最近的研究发现,miRNAs参与CSCs的分化、自我更新等生物学特性的调控。miRNAs可以作为CSCs研究的一个新的切入点。本文就近年来该方面的研究进展做简要综述。     

Targeting cancer stem cells by curcumin and clinical applications

Curcumin is a well-known dietary polyphenol derived from the rhizomes of turmeric, an Indian spice. The anticancer effect of curcumin has been demonstrated in many cell and animal studies, and recent research has shown that curcumin can target cancer stem cells (CSCs). CSCs are proposed to be responsible for initiating and maintaining cancer, and contribute to recurrence and drug resistance. A number of studies have suggested that curcumin has the potential to target CSCs through regulation of CSC self-renewal pathways (Wnt/β-catenin, Notch, sonic hedgehog) and specific microRNAs involved in acquisition of epithelial–mesenchymal transition (EMT). The potential impact of curcumin, alone or in combination with other anticancer agents, on CSCs was evaluated as well. Furthermore, the safety and tolerability of curcumin have been well-established by numerous clinical studies. Importantly, the low bioavailability of curcumin has been dramatically improved through the use of structural analogues or special formulations. More clinical trials are underway to investigate the efficacy of this promising agent in cancer chemoprevention and therapy. In this article, we review the effects of curcumin on CSC self-renewal pathways and specific microRNAs, as well as its safety and efficacy in recent human studies. In conclusion, curcumin could be a very promising adjunct to traditional cancer treatments.     

In vitro models of cancer stem cells and clinical applications

Cancer cells, stem cells and cancer stem cells have for a long time played a significant role in the biomedical sciences. Though cancer therapy is more effective than it was a few years ago, the truth is that still none of the current non-surgical treatments can cure cancer effectively. The reason could be due to the subpopulation called “cancer stem cells” (CSCs), being defined as those cells within a tumour that have properties of stem cells: self-renewal and the ability for differentiation into multiple cell types that occur in tumours.The phenomenon of CSCs is based on their resistance to many of the current cancer therapies, which results in tumour relapse. Although further investigation regarding CSCs is still needed, there is already evidence that these cells may play an important role in the prognosis of cancer, progression and therapeutic strategy. Therefore, long-term patient survival may depend on the elimination of CSCs. Consequently, isolation of pure CSC populations or reprogramming of cancer cells into CSCs, from cancer cell lines or primary tumours, would be a useful tool to gain an in-depth knowledge about heterogeneity and plasticity of CSC phenotypes and therefore carcinogenesis. Herein, we will discuss current CSC models, methods used to characterize CSCs, candidate markers, characteristic signalling pathways and clinical applications of CSCs. Some examples of CSC-specific treatments that are currently in early clinical phases will also be presented in this review.     

上皮间质转化参与CSC生成及其调控

肿瘤组织中存在一小部分具有无限增殖、自我更新、分化潜能、放化疗耐受以及高致瘤能力等干细胞特性的肿瘤干细胞（cancer stem cells,CSC）,它们是肿瘤无法治愈并不断进展的重要原因。许多与诱导肿瘤细胞上皮间质转化（epithelial-to-mesenchymal transition,EMT）相关的信号通路与CSC 的生成及调控相关。本综述简要阐述了EMT 与CSC 生成及调控相关的研究进展。     

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.     

Lung cancer stem cells: a biological and clinical perspective

Introduction

Lung cancer is the most lethal form of cancer in the world and despite significant therapeutic improvements that have been made, its survival rate still remains low. The latter is mainly due to the acquisition of resistance to systemic treatment regimens which, in turn, may be due to the presence of cancer stem cells (CSCs) within the primary tumors. CSCs constitute a subpopulation of cells that are highly tumorigenic and that exhibit biological properties similar to those of normal tissue stem cells, including an unlimited self-renewal capacity, an extensive proliferative capacity and a capacity to generate differentiated progeny. A better understanding of the signaling pathways that regulate lung CSC maintenance, proliferation, and tumorigenicity could thus lead to the design of improved approaches to lung cancer treatment.

Aim

In this review we will discuss the current knowledge on lung CSCs, their biological properties and their putative clinical relevance. By employing currently available data, we will evaluate the prognostic value of several lung CSC markers. In addition, we will discuss the release of CSCs from tumor tissue into the blood circulation via epithelial-mesenchymal transition (EMT) as an important step towards acquiring a metastatic phenotype. Finally, we will provide an outlook into novel CSC-targeting approaches for achieving less invasive diagnostic procedures and improving long-term therapeutic options.

Conclusion

Lung CSC research has gained considerable momentum to both basic and clinical applications, both aiming to identify a reliable panel of markers for lung CSCs and to clarify their function, with the final goal to develop a CSC-targeted therapy that will result in the complete elimination of CSCs for achieving significantly better long-time survival of lung cancer patients.     

Strategies to eliminate cancer stem cells: clinical implications

Over the past two decades, major advances in our understanding of cancer have translated into only modest increments in survival for the majority of cancer patients. Recent data suggesting cancers arise from rare self-renewing stem cells that are biologically distinct from their more numerous differentiated progeny may explain this paradox. Current anticancer therapies have been developed to decrease the bulk of the tumour mass (i.e. the differentiated cancer cells). Although treatments directed against the bulk of the cancer may produce dramatic responses, they are unlikely to result in long-term remissions if the rare cancer stem cells are also not targeted. Conversely, treatments that selectively attack cancer stem cells will not immediately eliminate the differentiated cancer cells, and might therefore be prematurely abandoned if clinical activity is judged solely by traditional response criteria that reflect changes in the bulk of the tumour. Re-examining both our pre-clinical and clinical drug development paradigms to include the cancer stem cell concept has the potential to revolutionize the treatment of many cancers.     

Dynamic equilibrium between cancer stem cells and non-stem cancer cells in human SW620 and MCF-7 cancer cell populations

Background:

Cancer stem cells (CSCs) paradigm suggests that CSCs might have important clinical implications in cancer therapy. Previously, we reported that accumulation efficiency of CSCs is different post low- and high-LET irradiation in 48 h.

Methods:

Cancer stem cells and non-stem cancer cells (NSCCs) were sorted and functionally identified through a variety of assays such as antigen profiles and sphere formation. Inter-conversion between CSCs and NSCCs were in situ visualised. Cancer stem cells proportions were assayed over multiple generations under normal and irradiation surroundings. Supplement and inhibition of TGF-β1, as well as immunofluorescence assay of E-cadherin and Vimentin, were performed.

Results:

Surface antigen markers of CSCs and NSCCs exist in an intrinsic homoeostasis state with spontaneous and in situ visualisable inter-conversions, irrespective of prior radiations. Supplement with TGF-β1 accelerates the equilibrium, whereas inhibition of TGF-β signalling disturbs the equilibrium and significantly decreases CSC proportion. Epithelial mesenchymal transition (EMT) might be activated during the process.

Conclusion:

Our results indicate that the intrinsic inter-conversion and dynamic equilibrium between CSCs and NSCCs exist under normal and irradiation surroundings, and TGF-β might have important roles in the equilibrium through activating EMT.     

Implications of Stem Cells and Cancer Stem Cells for Understanding Fomation and Therapy of Cancer

Most cancers are heterogeneous with respect to proliferation and differentiation. There is increasing evidence suggesting that only a minority of cancer cells, tumorigenic or tumor initiating cells, possess the capacity to proliferate extensively and form new hematopoietic cancer or solid tumors. Tumor initiating cells share characteristics required for normal stem cells. The dysregulation of self-renewal and proliferation of stem cells is a likely requirement for cancer development. This review formulates a model for the origin of cancer stem cells and regulating self-renewal which influences the way we study and treat cancer.     

Contextual regulation of pancreatic cancer stem cell phenotype and radioresistance by pancreatic stellate cells

Background and purpose

Progression of pancreatic ductal adenocarcinoma (PDAC) is promoted by desmoplasia induced by pancreatic stellate cells (PSC). Contributory to this progression is epithelial mesenchymal transition (EMT), which shares many characteristics with the cancer stem cell (CSC) hypothesis. We investigated the role of these processes on the radioresponse and tumorigenicity of pancreatic cancer cells.

Materials and methods

We used an in vitro sphere model and in vivo xenograft model to examine the role of PSC in EMT and CSC processes.

Results

We demonstrated that PSC enhanced the CSC phenotype and radioresistance of pancreatic cancer cells. Furthermore, the expression of several EMT and CSC markers supported enhanced processes in our models and that translated into remarkable in vivo tumorigenicity. Multi-dose TGFβ neutralizing antibody inhibited the EMT and CSC processes, sensitized cells to radiation and reduced in vivo tumorigenicity. A proteomic screen identified multiple novel factors that were regulated by PSC in pancreatic cells.

Conclusion

These results are critical in highlighting the role of PSC in tumor progression and radioresistance by manipulating the EMT and CSC processes. TGFβ and the novel factors identified are important targets for better therapeutic outcome in response to PSC mediated mechanisms.