Characterisation of normal and cancer stem cells: One experimental paradigm for two kinds of stem cells

The characterisation of normal stem cells and cancer stem cells uses the same paradigm. These cells are isolated by a fluorescence‐activated cell sorting step and their stemness is assayed following implantation into animals. However, differences exist between these two kinds of stem cells. Therefore, the translation of the experimental procedures used for normal stem cell isolation into the research field of cancer stem cells is a potential source of artefacts. In addition, normal stem cell therapy has the objective of regenerating a tissue, while cancer stem cell‐centred therapy seeks the destruction of the cancer tissue. Taking these differences into account is critical for anticipating problems that might arise in cancer stem cell‐centred therapy and for upgrading the cancer stem cell paradigm accordingly.     

Using ABCG2-molecule-expressing side population cells to identify cancer stem-like cells in a human ovarian cell line

CSCs (cancer stem cells) are a small subset of cells within a tumour that possesses the characteristics of stem cells and are considered to be responsible for resistance to chemoradiation. Identification of CSCs through stem cell characteristics might have relevant clinical implications. In this study, SP (side population ) cells were sorted from a human ovarian cancer cell line by FACS to determine whether cancer stem cell-like SP cells were present. A very small fraction of SP cells (2.6%) was detected in A2780 cells. SP cells possessed the following characteristics: highly proliferative activity, marked ability for self-renewal in soft agar and culture medium, high expression of ABCG2, drug resistance to vinblastine in vitro, and strong tumourigenic potential in Balb/c nude mice. It is concluded that there exists in the A2780 cell line a small number of SP cells with high expression of ABCG2. The cells have the characteristics of cancer stem-like cells, and identification and cloning of such human SP cells can help in improving therapeutic approaches to ovarian cancer in patients.     

Ubiquitin ligase CHIP suppresses cancer stem cell properties in a population of breast cancer cells

Cancer stem cells (CSCs) have several distinctive characteristics, including high metastatic potential, tumor-initiating potential, and properties that resemble normal stem cells such as self-renewal, differentiation, and drug efflux. Because of these characteristics, CSC is regarded to be responsible for cancer progression and patient prognosis. In our previous study, we showed that a ubiquitin E3 ligase carboxyl terminus of Hsc70-interacting protein (CHIP) suppressed breast cancer malignancy. Moreover, a recent clinical study reported that CHIP expression levels were associated with favorable prognostic parameters of patients with breast cancer. Here we show that CHIP suppresses CSC properties in a population of breast cancer cells. CHIP depletion resulted in an increased proportion of CSCs among breast cancers when using several assays to assess CSC properties. From our results, we propose that inhibition of CSC properties may be one of the functions of CHIP as a suppressor of cancer progression.     

Aldehyde dehydrogenase 1 is a putative marker for cancer stem cells in head and neck squamous cancer

Aldehyde dehydrogenase 1 (ALDH1) has been considered to be a marker for cancer stem cells. However, the role of ALDH1 in head and neck squamous cell carcinoma (HNSCC) has yet to be determined. In this study, we isolated ALDH1-positive cells from HNSCC patients and showed that these HNSCC-ALDH1⁺ cells displayed radioresistance and represented a reservoir for generating tumors. Based on microarray findings, the results of Western blotting and immunofluorescent assays further confirmed that ALDH1⁺-lineage cells showed evidence of having epithelial-mesenchymal transition (EMT) shifting and endogenously co-expressed Snail. Furthermore, the knockdown of Snail expression significantly decreased the expression of ALDH1, inhibited cancer stem-like properties, and blocked the tumorigenic abilities of CD44⁺CD24⁻ALDH1⁺ cells. Finally, in a xenotransplanted tumorigenicity study, we confirmed that the treatment effect of chemoradiotherapy for ALDH1⁺ could be improved by Snail siRNA. In summary, it is likely that ALDH1 is a specific marker for the cancer stem-like cells of HNSCC.     

The most reliable surface marker for the identification of colorectal cancer stem-like cells: A systematic review and meta-analysis

Several surface markers have been proposed for the identification and characterization of colorectal cancer stem-like cells (CR-CSLCs). However, their reliability in CR-CSLCs identification remains controversial. This study evaluated the correlation between all candidate surface marker's expression and CSLCs properties (tumorigenicity) through monitoring in vivo tumor incidence and final tumor volume. PubMed, Web of Science, and Scopus databases were systematically searched until November 2017. A total of 27 studies were found that met the inclusion criteria for cluster of differentiation 133 (CD133) and CD44 markers. Results indicated that either CD133 or CD44 positive cells caused about twofold increase in tumor volume compared with the negative cells (p < 0.05). In two groups of cells derived from primary tumors and cell lines, CD133 ⁺ cells had 25 and 1.45 times higher tumor incidence potential than CD133 ⁻ cells, respectively ( p < 0.05). Also, cohort evaluation showed that CD133 overexpression at protein level is a marker of poor overall survival in colorectal cancer (CRC) patients. While CD44 ⁺ cells displayed twofold tumorigenicity compared with the negative cells ( p < 0.05), combination of CD44 and CD133 showed about sevenfold tumorigenicity potential ( p < 0.05). In conclusion, the present meta-analysis suggests that CD133 is a robust biomarker to identify primary tumor CSLCs and can be proposed as a prognostic marker of CRC patient whereas it should be used with caution in cell lines. It seems to be more reliable to use CD133 in combination with CD44 as target biomarkers for the isolation of CR-CSLCs in both cell line and primary tumor cells populations.     

Quiescent stem cells in intestinal homeostasis and cancer

Abstract

Adult stem cell niches are characterized by a dichotomy of cycling and quiescent stem cells: while the former are responsible for tissue turnover, their quiescent counterparts are thought to become active upon tissue injury thus underlying the regenerative response. Moreover, quiescence prevents adult stem cells from accumulating mutations thus ensuring a reservoir of unaltered stem cells. In the intestine, while cycling stem cells were shown to give rise to the main differentiated lineages, the identity of their quiescent equivalents remains to date elusive. This is of relevance for conditions such as Crohn's disease and ulcerative colitis where quiescent stem cells may underlie metaplasia and the increased cancer risk associated with chronic inflammation. Tumours are thought to share a comparable hierarchical structure of adult tissues with pluripotent and self-renewing cancer stem cells (CSCs) giving rise to more differentiated cellular types. As such, neoplastic lesions may encompass both cycling and quiescent CSCs. Because of their infrequent cycling, quiescent CSCs are refractory to chemo- and radiotherapy and are likely to play a role in tumour dissemination, dormancy and recurrence.     

乳腺癌干细胞分子特性及其治疗新策略

乳腺癌是一种严重影响女性健康甚至危及生命的疾病。环境、饮食习惯、疾病等均有可能诱发人类乳腺细胞癌基因活化或抑癌基因失活,其诱发过程可通过细胞、动物模型所证实。最新研究指出,乳腺癌肿瘤干细胞的分子特性研究为乳腺癌发生、发展的认识提供了重要的佐证。另外,MicroRNAs在乳腺癌中表现促进或抑制瘤细胞生长与分化。这些研究的深入开展将为乳腺癌的防治提供新思路。     

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.     

肿瘤干细胞与表观遗传学调控

关于恶性肿瘤发生、复发与转移机制的研究由来已久,但目前的临床治疗方法依然不能克服肿瘤复发与转移的难题,肿瘤患者的生存率并未得到显著改善。近年来的研究提示肿瘤的起源、复发与转移的真正原因可能是存在于肿瘤内的极少数具有干细胞特性的细胞,即肿瘤干细胞（cancer stem cells,CSC）。与此同时,越来越多的研究表明,对于肿瘤干细胞的发生与功能维持,表观遗传学的调控机制可能发挥着极其重要的作用。该文简要综述目前肿瘤干细胞和表观遗传学相关领域的研究进展,并对肿瘤干细胞形成及发展过程中表观遗传学的调控作用及机制进行重点介绍。     

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。     

miRNA-148b suppresses hepatic cancer stem cell by targeting neuropilin-1

The existence of cancer stem cells (CSCs) is considered as a direct reason for the failure of clinic treatment in hepatocellular carcinoma (HCC). Growing evidences have demonstrated that miRNAs play an important role in regulation of stem cell proliferation, differentiation and self-renewal and their aberrances cause the formation of CSCs and eventually result in carcinogenesis. We recently identified miRNA-148b as one of the miRNAs specifically down-regulated in side population (SP) cells of PLC/PRF/5 cell line. However, it remains elusive how miRNA-148b regulates CSC properties in HCC. In the present study, we observed that overexpression or knockdown of miR-148b through lentiviral transfection could affect the proportion of SP cells as well as CSC-related gene expression in HCC cell lines. In addition, miR-148b blocking could stimulate cell proliferation, enhance chemosensitivity, as well as increase cell metastasis and angiogenesis in vitro. More importantly, miR-148b could significantly suppress tumorigenicity in vivo. Further studies revealed that Neuropilin-1 (NRP1), a transmembrane co-receptor involved in tumour initiation, metastasis and angiogenesis, might be the direct target of miRNA-148b. Taking together, our findings define that miR-148b might play a critical role in maintenance of SP cells with CSC properties by targeting NRP1 in HCC. It is the potential to develop a new strategy specifically targeting hepatic CSCs (HCSCs) through restoration of miR-148b expression in future therapy.     

肺干细胞和肺癌干细胞研究进展

近年来成体干细胞研究进展迅速。肺干细胞和肺癌干细胞在表面标志、分离方法和功能研究等方面也取得了一定进展。在肺组织中,肺干细胞维持着肺上皮的更新和稳定,肺脏不同解剖结构存在不同的干细胞,主要的肺干细胞有气管—支气管干细胞、细支气管干细胞、细支气管肺泡干细胞和肺泡干细胞等,不同干细胞特异表面标志也不同。根据肿瘤干细胞理论,目前研究认为肺癌的发生与肺癌干细胞有关,肺癌干细胞来源于其对应肺干细胞的恶性转化。肺癌干细胞特异标志研究主要集中在侧群细胞、CD133和醛脱氢酶等。与其他成体干细胞相似,肺癌干细胞维持自我更新以及分化能力的信号通路主要有Wnt、Hedgehog和Notch通路等。肺癌干细胞与肺癌的发生、发展、转移、治疗反应及预后关系,也取得了一定的进展。该文对肺干细胞和肺癌干细胞研究进展作简要综述。     

Triptolide inhibits CD133+/CD44+ colon cancer stem cell growth and migration through triggering apoptosis and represses epithelial-mesenchymal transition via downregulating expressions of snail,slug, and twist

High recurrence and metastatic behavior patterns are the most important reasons for the failure of treatment strategies in patients with colon cancer. Cancer stem cells (CSCs), which are considered root of cancer, are thought to be associated with therapy resistance, relapse, and metastasis, and, therefore, targeting CSCs rather than the bulk population may be an effective approach. In cancer studies, there is an increasing interest in close friendship between epithelial-mesenchymal transition (EMT) and CSCs. Triptolide (TPL) isolated from Chinese herb Tripterygium wilfordii has important effects on the prevention of migration and metastasis as well as cytotoxic effect against cancer cells. The potential lethal efficacy of TPL on CSCs that is highly resistant to the drug is an unsolved mystery. Fundamentally, the present study basically aims to find answers to two questions: (a) is it possible to target colon CSCs with TPL? and (b) what are the mechanisms underlying TPL's potential to eliminate CSCs? Cytotoxic effects of TPL on CSCs were evaluated by WST-1 and Muse count and viability assays. Apoptosis assay and cell-cycle analysis were performed to investigate the inhibitory effect of TPL. Moreover, the effects of TPL on spheroid formation capacity, migration, and EMT processes, which are associated with CSC phenotype, were also investigated. The results revealed that TPL triggered cell death and apoptosis and altered cell cycle distribution. Moreover, TPL significantly reduced the snail slug and twist expressions associated with EMT. TPL has been shown to be effective in colon CSCs by in vitro experiments, and it might be a highly effective agent against colon cancer has been implicated in need of supporting in vivo and clinical studies.     

Developments in techniques for the isolation,enrichment, main culture conditions and identification of spermatogonial stem cells

The in vitro culture system of spermatogonial stem cells (SSCs) provides a basis for studies on spermatogenesis, and also contributes to the development of new methods for the preservation of livestock and animal genetic modification. In vitro culture systems have mainly been established for mouse SSCs, but are lacking for farm animals. We reviewed and analyzed the current progress in SSC techniques such as isolation, purification, cultivation and identification. Based on the published studies, we concluded that two-step enzyme digestion and magnetic-activated cell sorting are fast becoming the main methods for isolation and enrichment of SSCs. With regard to the culture systems, serum and feeders were earlier thought to play an important role in the self-renewal and proliferation of SSCs, but serum- and feeder-free culture systems as a means of overcoming the limitations of SSC differentiation in long-term SSC culture are being explored. However, there is still a need to establish more efficient and ideal culture systems that can also be used for SSC culture in larger mammals. Although the lack of SSC-specific surface markers has seriously affected the efficiency of purification and identification, the transgenic study is helpful for our identification of SSCs. Therefore, future studies on SSC techniques should focus on improving serum- and feeder-free culture techniques, and discovering and identifying specific surface markers of SSCs, which will provide new ideas for the optimization of SSC culture systems for mice and promote related studies in farm animals.     

肿瘤干细胞的生物学特性及其研究进展

肿瘤干细胞(cancer stem cells,CSC)是肿瘤组织中存在的一类干细胞,具有自我更新、无限增殖能力及致瘤性。大量研究显示,血液系统及实体瘤中均存在CSC。综述了CSC生物学特性的最新研究进展,包括寻找表面标记物、确定CSC微环境、分选与鉴定CSC、探索肿瘤细z胞和CSC之间的转化、研究CSC耐药性和耐药机制。利用肿瘤的这些生物学特性选择性杀伤肿瘤干细胞的靶分子疗法,为克服肿瘤耐药的复发与转移提供新的策略。CSC的研究为人们对肿瘤生物学特性的进一步认识提供了新的思路,并为肿瘤的临床治疗提供了新的希望。     

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。     

Pancreatic cancer stem cells and relevance to cancer treatments

Pancreatic cancer continues to be a malignancy with few therapeutic options. The majority of patients that present for an evaluation have locally advanced or metastatic disease that is incurable by surgical approaches. Chemotherapy and radiotherapy resistance of pancreatic adenocarcinomas limits the efficacy of these therapeutic approaches. Recent evidence supports the existence of human pancreatic cancer stem cells, which appear to drive tumor initiation and progression and are particularly resistant to cell death induced by radiation or chemotherapy. Understanding the mechanisms of pancreatic cancer stem cell self‐renewal and resistance to standard therapies may lead to new, more effective therapies to treat this dismal disease. J. Cell. Biochem. 107: 40–45, 2009. © 2009 Wiley‐Liss, Inc.