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.     

Ovarian cancer stem cell markers: Prognostic and therapeutic implications

Cancer stem cells are rare chemotherapy resistant cells within a tumor which can serve to populate the bulk of a tumor with more differentiated daughter cells and potentially contribute to recurrent disease. Ovarian cancer is a disease for which at the time of initial treatment we can obtain complete clinical remission in the majority of patients. Unfortunately, most will relapse and succumb to their disease. This clinical course is in line with the cancer stem cell model. In the past 5 years a significant amount of work has been done to identify cells with characteristics of ovarian cancer stem cells. This review will focus specifically on the markers used to define human ovarian cancer stem cells, the prognostic implications of the expression of these cancer stem cell markers in patient’s primary tumors, and the potential of these cancer stem cell markers to serve as therapeutic targets.     

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。     

Cancer Stem Cells and Stemness Markers in Oral Squamous Cell Carcinomas

Head and neck squamous cell carcinoma (HNSCC) is one of the world top ten most common cancers withits highest occurrence in the Indian subcontinent and different aggressive and etiological behavioural patterns.The scenario is only getting worst with the 5 year survival rates dropping to 50%, persistent treatment failuresand frequent cases of relapse/recurrence. One of the major reasons for these failures is the presence of cancerstem cells (CSCs), a small population of cancer cells that are highly tumourigenic, capable of self-renewal andhave the ability to differentiate into cells that constitute the bulk of tumours. Notably, recent evidence suggeststhat cancer stem cells are especially resistant to conventional therapy and are the “drivers” of local recurrenceand metastatic spread. Specific markers for this population have been investigated in HNSCC in the hope ofdeveloping a deeper understanding of their role in oral cancer pathogenesis, elucidating novel biomarkers forearly diagnosis and newer therapeutic strategies. This review covers the fundamental relevance of almost all theCSC biomarkers established to date with a special emphasis on their impact in the process of oral tumourigenesisand their potential role in improving the diagnosis, prognosis and treatment of OSCC patients.     

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.     

circRNA MYO1C对肺癌细胞自噬和肿瘤干细胞分化的影响

目的 探讨环状RNA(circRNA)MYO1C对非小细胞肺癌(NSCLC)细胞自噬和肿瘤干细胞(Cancer stem cells,CSCs)分化的影响。方法 通过RT-qPCR检测正常肺上皮细胞和NSCLC A549细胞中circRNA MYO1C水平。将A549分为对照组、NC组和siMYO1C组,通过转染si-circRNA MYO1C质粒干扰circRNA MYO1C。用CCK-8法和Transwell实验检测细胞生长活力和迁移能力。通过Western blot检测CSCs分化标志蛋白(OCT4、SOX2和NANOG)以及自噬标志蛋白(P62和IC3II/LC3I)的表达水平。结果 相对正常肺上皮细胞,circRNA MYO1C在A549细胞中表达明显上调(0.99±0.06 vs. 4.87±0.88,P=0.002)。与NC组比较,siMYO1C组细胞中circRNA MYO1C水平、细胞活力、迁移、OCT4、SOX2、NANOG和IC3II/LC3I蛋白水平显著降低,而P62蛋白水平显著升高(P＜0.001)。结论 下调circRNA MYO1C能够抑制NSLCLC细胞的CSCs分化和自噬相关蛋白表达,并抑制肺癌细胞迁移。     

TMPRSS4 correlates with colorectal cancer pathological stage and regulates cell proliferation and self-renewal ability

Transmembrane protease/serine 4 (TMPRSS4) is a member of the type II transmembrane serine protease (TTSP) family and it was found highly expressed in several cancers. This study aims to evaluate the expression of TMPRSS4 in colorectal cancer (CRC) and investigate its role in proliferation and self-renewal of colon cancer cells. qRT-PCR and immunohistochemistry were used to detect the mRNA and protein expression level of TMRPSS4 in CRC samples respectively. Loss of function assay was conducted with RNAi technique. Cell proliferation was done with WST-8 assay; cell apoptosis and cell cycle analysis were performed with flow cytometry; invasion and migration were done with transwell assay. Plate and soft agarose clonogenic assays were used to detect clone-formation ability. CD44 and CD133 expressions were analyzed by flow cytometry and western blot. We found that TMPRSS4 was highly expressed in CRC tissues both at mRNA and protein level and correlated with pathological stage. Knockdown of TMPRSS4 in highly expressed colon cancer cell line HCT116 resulted in inhibition of cell proliferation, induction of cell apoptosis and suppression of invasion and migration; moreover, knockdown of TMPRSS4 suppressed the in vitro clone-formation ability of HCT116 and reduced the expressions of CD44 and CD133. The findings in this research showed that TMPRSS4 was associated with CRC stage and regulated the proliferation and self-renewal ability of colon cancer cells; TMRPSS4 was involved in the development and progression of CRC.     

PDCD2 functions in cancer cell proliferation and predicts relapsed leukemia

PDCD2 is an evolutionarily conserved eukaryotic protein with unknown function. The Drosophila PDCD2 ortholog Zfrp8 has an essential function in fly hematopoiesis. Zfrp8 mutants exhibit marked lymph gland hyperplasia that results from increased proliferation of partially differentiated hemocytes, suggesting Zfrp8 may participate in cell growth. Based on the above observations we have focused on the role of PDCD2 in human cancer cell proliferation and hypothesized that aberrant PDCD2 expression may be characteristic of human malignancies. We report that PDCD2 is highly expressed in human acute leukemia cells as well as in normal hematopoietic progenitors. PDCD2 knockdown in cancer cells impairs their proliferation, but not viability relative to parental cells, supporting the notion that PDCD2 overexpression facilitates cancer cell growth. Prospective analysis of PDCD2 in acute leukemia patients indicates PDCD2 RNA expression correlates with disease status and is a significant predictor of clinical relapse. PDCD2’s role in cell proliferation and its high expression in human malignancies make it an attractive, novel potential molecular target for new anti-cancer therapies.     

A novel approach to the identification and enrichment of cancer stem cells from a cultured human glioma cell line

Enrichment of cancer stem cells for studies of carcinogenesis remains a difficult issue. We hypothesized that the unique features of cancer stem cells (CSCs) may allow formation of their colonies in vitro with distinct morphology. We therefore investigated the possibility to use morphological diversity of colonies to identify and enrich CSCs from cultured malignant human glioma cells. We found that a small proportion of the cells from a human glioma cell line U251 formed tight and round-shaped colonies in culture. Most cells in such colonies were capable of self-renewal, generating tumor spheres and differentiating into lineages with markers for neurons, astrocytes and oligodendrocytes. In addition, several neural stem cell-related genes were highly expressed by tumor cells in those tight colonies. Our results thus demonstrate a novel approach to the identification and enrichment of CSCs based on unique morphology of their colonies formed in vitro.     

Targeting cancer stem cells: a new therapy to cure cancer patients

Cancer stem cells (CSCs) have been defined as cells within tumor that possess the capacity to self-renew and to cause the heterogeneous lineages of cancer cells that comprise the tumor. They have been identified in blood, breast, brain, colon, melanoma, pancreatic, prostate, ovarian, lung cancers and so on. It is often considered to be associated with chemo-resistance and radio-resistance that lead to the failure of traditional therapies. Most therapies are directed at the fast growing tumor mass but not the slow dividing cancer stem cells. Eradicating cancer stem cells, the root of cancer origin and recurrence, has been thought as a promising approach to improve cancer survival or even to cure cancer patients. Understanding the characteristics of cancer stem cells will help to develop novel therapies to eliminate the initiating cancer stem cell, and the relevant patents on the cancer stem cell and cancer therapy by cancer stem cells will be discussed.     

Role of microRNA221 in regulating normal mammary epithelial hierarchy and breast cancer stem-like cells

Increasing evidence suggests that lineage specific subpopulations and stem-like cells exist in normal and malignant breast tissues. Epigenetic mechanisms maintaining this hierarchical homeostasis remain to be investigated. In this study, we found the level of microRNA221 (miR-221) was higher in stem-like and myoepithelial cells than in luminal cells isolated from normal and malignant breast tissue. In normal breast cells, over-expression of miR-221 generated more myoepithelial cells whereas knock-down of miR-221 increased luminal cells. Over-expression of miR-221 stimulated stem-like cells in luminal type of cancer and the miR-221 level was correlated with clinical outcome in breast cancer patients. Epithelial-mesenchymal transition (EMT) was induced by overexpression of miR-221 in normal and breast cancer cells. The EMT related gene ATXN1 was found to be a miR-221 target gene regulating breast cell hierarchy. In conclusion, we propose that miR-221 contributes to lineage homeostasis of normal and malignant breast epithelium.     

To wake up cancer stem cells,or to let them sleep,that is the question

Cancer stem cells (CSCs) generate transient‐amplifying cells and thereby contribute to cancer propagation. A fuller understanding of the biological features of CSCs is expected to lead to the development of new anticancer therapies capable of eradicating this life‐threatening disease. Cancer stem cells are known to maintain a non‐proliferative state and to enter the cell cycle only infrequently. Given that conventional anticancer therapies preferentially target dividing cells, CSCs are resistant to such treatments, with those remaining after elimination of bulk cancer cells potentially giving rise to disease relapse and metastasis as they re‐enter the cell cycle after a period of latency. Targeting of the switch between quiescence and proliferation in CSCs is therefore a potential strategy for preventing the reinitiation of malignancy, underscoring the importance of elucidation of the mechanisms by which these cells are maintained in the quiescent state. The fundamental properties of CSCs are thought to be governed cooperatively by internal molecules and cues from the external microenvironment (stem cell niche). Several such intrinsic and extrinsic regulators are responsible for the control of cell cycle progression in CSCs. In this review, we address two opposite approaches to the therapeutic targeting of CSCs – wake‐up and hibernation therapies – that either promote or prevent the entry of CSCs into the cell cycle, respectively, and we discuss the potential advantages and risks of each strategy.     

Identification of a cancer stem-like population in the Lewis lung cancer cell line

Objective: Although various human cancer stem cells (CSCs) have been defined, their applications are restricted to immunocompromised models. Developing a novel CSC model which could be used in immunocompetent or transgenic mice is essential for further understanding of the biomolecular characteristics of tumor stem cells. Therefore, in this study, we analyzed murine lung cancer cells for the presence of CSCs. Methods: Side population (SP) cells were isolated by fluorescence activated cell sorting, followed by serum-free medium (SFM) culture, using Lewis lung carcinoma cell (LLC) line. The self-renewal, differentiated progeny, chemosensitivity, and tumorigenic properties in SP and non-SP cells were investigated through in vitro culture and in vivo serial transplantation. Differential expression profiles of stem cell markers were examined by RT-PCR. Results: The SP cell fraction comprised 1.1% of the total LLC population. SP cells were available to grow in SFM, and had significantly enhanced capacity for cell proliferation and colony formation. They were also more resistant to cisplatin in comparison to non-SP cells, and displayed increased tumorigenic ability. Moreover, SP cells showed higher mRNA expression of Oct-4, ABCG2, and CD44. Conclusion: We identified SP cells from a murine lung carcinoma, which possess well-known characteristics of CSCs. Our study established a useful model that should allow investigation of the biological features and pharmacosensitivity of lung CSCs, both in vitro and in syngeneic immunocompetent or transgenic/knockout mice.     

Characterization of sphere-forming cells with stem-like properties from the small cell lung cancer cell line H446

A relatively novel paradigm in tumor biology hypothesizes that cancer growth is driven by tumor cells with stem-like properties. However, direct proof of a population of stem cells in small cell lung cancer (SCLC) remains elusive. In this study, we enriched for stem-like cells from the SCLC cell line H446 by growing them as spheres in a defined serum-free medium. Sphere-derived cells have increased in vitro clonogenic and in vivo tumorigenic potentials as well as drug-resistant properties. After enrichment for stem-like cells, we used multiple candidate stem cell markers to examine the expression profile and found that the sphere-derived cells contained a higher proportion of cells expressing the stem cell surface markers uPAR and CD133 when compared with parental cells. To identify a selectable marker for the sphere-forming cells, we evaluated the sphere-forming abilities of uPAR(+) and uPAR(-) cells as well as the sphere-forming abilities of CD133(+) and CD133(-) cells. Both CD133(+) and CD133(-) cell fractions were capable of forming spheres, and no statistically significant difference was observed in the sphere-forming efficiency between these two populations. In contrast, cells derived from the uPAR(+) fraction were capable of forming spheres, whereas cells derived from the uPAR(-) fraction remained as single cells. Moreover, uPAR(+) cells efficiently formed transplantable tumors, whereas uPAR(-) cells were unable to initiate tumors when transplanted at equivalent cell numbers. In addition, uPAR(+) cells could differentiate into CD56(+)cells, CK(+) cells, and uPAR(-) cells. These data support the existence of a population of tumor sphere-forming cells with stem cell properties in the H446 SCLC cell line. Furthermore, the stem cell population may be enriched in cells expressing the uPAR cell surface marker.     

骨髓成纤维样基质细胞系对急性髓细胞白血病细胞系增殖与分化影响的研究

目的：以急性髓细胞白血病（acute myeloid leukaemia,AML）细胞系为研究对象,观察正常人骨髓成纤维样细胞系（human bone marrow fibro—blastoid stromal cell line,HFCL）对急性单核细胞白血病细胞系U937、急性粒细胞白血病敏感细胞HL-60和多药耐药细胞HL-60／VCR增殖和分化的影响。方法：建立U937、HL-60和HL-60／VCR细胞与HFCL细胞的共培养模型,实验分对照组、直接接触组和transwell组。采用台盼蓝拒染法测定生长曲线;硝基四氮唑蓝（NBT）确定细胞分化;流式细胞仪检测细胞周期和CD11b、CD13、CD14和CD33细胞表面抗原进一步鉴定细胞分化;west-ernblot检测增殖细胞核抗原（PCNA）和P-糖蛋白（P-gP）的表达。结果：与HFCL细胞共培养96h后,U937、HL-60和HL-60／VCR细胞的生长受抑,且与HFCL细胞直接接触组的抑制作用大于用tr-answell组,P〈0．01。同时发现AML细胞系与HFCL细胞共培养后,G0／G1期细胞比例均增高,而S期细胞均减少,P〈0．01;尤其是直接接触组CD11b和CD14表达也均增高（P〈0．01）,CD13和CD33变化不大,NBT阳性细胞轻度增高,且差异有统计学意义。Western blot检测结果显示,3种AML细胞系PCNA表达下调;以直接接触组为甚。提示介导着白血病细胞和骨髓基质细胞间的相互作用的整合素p1（VLA-4）和p2（LFA-1）,在HFCL细胞对AML细胞生长作用影响中起着不可忽视的作用。结论：HFCL对3种具有代表性的AML细胞系U937、HL-60和HL-60／VCR有增殖抑制和诱导分化作用,除了能抑制AML细胞的生长,抑制PCNA的表达,出现G0／G1期阻滞外,还能诱导其部分向单核细胞分化。     

结直肠癌肿瘤干细胞标志物的研究进展

近年来,肿瘤干细胞（CSC）学说得到越来越多的支持,识别CSC的关键就是寻找干细胞的表面特异性标志物.结直肠癌CSC的相关研究不断取得进展,文章综述了近几年发现的比较公认的干细胞标志物CD44、SOX9、ALDH1和OCT-4等的研究进展及其与结直肠癌的关系.     

小细胞肺癌干细胞信号通路的研究进展

小细胞肺癌是具有高度侵袭性的肺肿瘤,其主要临床特征是化疗有效率高但易在短时间内复发转移,这一特点可能与肿瘤干细胞的存在有关。肿瘤干细胞被认为是恶性肿瘤发生发展、耐药、复发及转移的根源。目前多认为肿瘤干细胞与正常干细胞有着相同的信号通路,如Hedgehog、Notch、Wnt等通路。本文就这几条信号通路在小细胞肺癌干细胞中所起的作用以及针对这几条信号通路治疗药物的研究进展和可能的信号通路交互作用等方面进行综述。     

肝癌干细胞与肝癌的研究进展

肿瘤起源于干细胞的假说已在人类许多实体瘤中得到证实,近来亦发现肝癌中存在肝癌干细胞.肿瘤干细胞被认为是肿瘤产生的根源,对肿瘤的发生、发展、转移、复发及耐药具有关键作用.因此,如何分离鉴定肝癌干细胞对于改善预防方法、促进早期检测以及研发新的治疗方法都是一个非常紧迫的课题.本文就肝癌干细胞的来源、表面标志、分选方法、应用前景及存在的问题作一综述.     

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.