CD133(+)EpCAM(+) phenotype possesses more characteristics of tumor initiating cells in hepatocellular carcinoma Huh7 cells

Background: EpCAM or CD133 has been used as the tumor initiating cells (TICs) marker in hepatocellular carcinoma (HCC). We investigated whether cells expressing with both EpCAM and CD133 surface marker were more representative for TICs in hepatocellular carcinoma Huh7 cells.Methods: Four different phenotypes of CD133⁺EpCAM⁺, CD133⁺EpCAM^-, CD133^-EpCAM⁺ and CD133^-EpCAM^- in Huh7 cells were sorted by flow cytometry. Then cell differentiation, self-renewal, drug-resistance, spheroid formation and the levels of stem cell-related genes were detected to compare the characteristics of TICs. The ability of tumorigenicity was measured in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice to verify TICs.Results: CD133⁺EpCAM⁺ cells have many characteristics of TICs in Huh7 cells compared with CD133⁺EpCAM^-, CD133^-EpCAM⁺, CD133^-EpCAM^- cells, including enrichment in side population cells, higher differentiation capacity, increased colony-formation ability, preferential expression of stem cell-related genes, appearance of drug-resistant to some chemotherapeutics, more spheroid formation of culture cells and stronger tumorigenicity in NOD/SCID mice.Conclusion: CD133⁺EpCAM⁺ phenotype is precisely represented TICs in Huh7 cells. It might be useful for studying biology mechanism of TICs in hepatocellular carcinoma and screening new targets for cancer therapy.     

Down‐expression of miR‐154 suppresses tumourigenesis in CD133+ glioblastoma stem cells

Glioblastoma multiforme (GBM) is the most common and aggressive form of brain cancer. Evidences have suggested that CD133 is a marker for a subset of glioblastoma cancer stem cells. However, whether miRNA plays a critical role in CD133⁺ GBM is poorly understood. Here, we identified that miR‐154 was upregulated in CD133⁺ GBM cell lines. Knockdown of miR‐154 remarkably suppressed proliferation and migration of CD133⁺ GBM cells. Further study found that PRPS1 was a direct target of miR‐154 in CD133⁺ GBM cells. Overexpression of PRPS1 exhibited similar effects as miR‐154 knockdown in CD133⁺ GBMs. Our study identified miR‐154 as a previously unrecognized positive regulator of proliferation and migration in CD133⁺ GBM cells and a potentially therapeutic target of GBMs. Copyright © 2016 John Wiley & Sons, Ltd.     

DEAD/H (Asp–Glu–Ala–Asp/His) box polypeptide 3, X-linked is an immunogenic target of cancer stem cells

Accumulating evidence suggests that most solid malignancies consist of heterogeneous tumor cells and that a relatively small subpopulation, which shares biological features with stem cells, survives through potentially lethal stresses such as chemotherapy and radiation treatment. Since the survival of this subpopulation of cancer stem cells (CSC) plays a critical role in recurrence, it must be eradicated in order to cure cancer. We previously reported that vaccination with CD133⁺ murine melanoma cells exhibiting biological CSC features induced CSC-specific effector T cells. These were capable of eradicating CD133⁺ tumor cells in vivo, thereby curing the parental tumor. In the current study, we indicated that DEAD/H (Asp–Glu–Ala–Asp/His) box polypeptide 3, X-linked (DDX3X) is an immunogenic protein preferentially expressed in CD133⁺ tumor cells. Vaccination with DDX3X primed specific T cells, resulting in protective and therapeutic antitumor immunity. The DDX3X-primed CD4⁺ T cells produced CD133⁺ tumor-specific IFNγ and IL-17 and mediated potent antitumor therapeutic efficacy. DDX3X is expressed in various human cancer cells, including lung, colon, and breast cancer cells. These results suggest that anti-DDX3X immunotherapy is a promising treatment option in efforts to eradicate CSC in the clinical setting.     

Radiation-induced glioblastoma signaling cascade regulates viability,apoptosis and differentiation of neural stem cells (NSC)

Ionizing radiation alone or in combination with chemotherapy is the main treatment modality for brain tumors including glioblastoma. Adult neurons and astrocytes demonstrate substantial radioresistance; in contrast, human neural stem cells (NSC) are highly sensitive to radiation via induction of apoptosis. Irradiation of tumor cells has the potential risk of affecting the viability and function of NSC. In this study, we have evaluated the effects of irradiated glioblastoma cells on viability, proliferation and differentiation potential of non-irradiated (bystander) NSC through radiation-induced signaling cascades. Using media transfer experiments, we demonstrated significant effects of the U87MG glioblastoma secretome after gamma-irradiation on apoptosis in non-irradiated NSC. Addition of anti-TRAIL antibody to the transferred media partially suppressed apoptosis in NSC. Furthermore, we observed a dramatic increase in the production and secretion of IL8, TGFβ1 and IL6 by irradiated glioblastoma cells, which could promote glioblastoma cell survival and modify the effects of death factors in bystander NSC. While differentiation of NSC into neurons and astrocytes occurred efficiently with the corresponding differentiation media, pretreatment of NSC for 8 h with medium from irradiated glioblastoma cells selectively suppressed the differentiation of NSC into neurons, but not into astrocytes. Exogenous IL8 and TGFβ1 increased NSC/NPC survival, but also suppressed neuronal differentiation. On the other hand, IL6 was known to positively affect survival and differentiation of astrocyte progenitors. We established a U87MG neurosphere culture that was substantially enriched by SOX2⁺ and CD133⁺ glioma stem-like cells (GSC). Gamma-irradiation up-regulated apoptotic death in GSC via the FasL/Fas pathway. Media transfer experiments from irradiated GSC to non-targeted NSC again demonstrated induction of apoptosis and suppression of neuronal differentiation of NSC. In summary, intercellular communication between glioblastoma cells and bystander NSC/NPC could be involved in the amplification of cancer pathology in the brain.     

miR-30 family promotes migratory and invasive abilities in CD133<Superscript>+</Superscript> pancreatic cancer stem-like cells

Pancreatic cancer is a deadly disease with a poor prognosis. Recently, miRNAs have been reported to be abnormally expressed in several cancers and play a role in cancer development and progression. However, the role of miRNA in cancer stem cells remains unclear. Therefore, our aim was to investigate the role of miRNA in the CD133⁺ pancreatic cancer cell line Capan-1M9 because CD133 is a putative marker of pancreatic cancer stem cells. Using miRNA microarray, we found that the expression level of the miR-30 family decreased in CD133 genetic knockdown shCD133 Capan-1M9 cells. We focused on miR-30a, -30b, and -30c in the miR-30 family and created pancreatic cancer cell sublines, each transfected with these miRNAs. High expression of miR-30a, -30b, or -30c had no effect on cell proliferation and sphere forming. In contrast, these sublines were resistant to gemcitabine, which is a standard anticancer drug for pancreatic cancer, and in addition, promoted migration and invasion. Moreover, mesenchymal markers were up-regulated by these miRNAs, suggesting that mesenchymal phenotype is associated with an increase in migration and invasion. Thus, our study demonstrated that high expression of the miR-30 family modulated by CD133 promotes migratory and invasive abilities in CD133⁺ pancreatic cancer cells. These findings suggest that targeted therapies to the miR-30 family contribute to the development of novel therapies for CD133⁺ pancreatic cancer stem cells.     

Uncoupling Warburg effect and stemness in CD133<Superscript>+ve</Superscript> cancer stem cells from Saos-2 (osteosarcoma) cell line under hypoxia

Cancer stem cells (CSCs) which are known to be residing deep inside the core of the tumor in its hypoxia niche is responsible for relapse of cancers. Owing to this hypoxic niche, the residing CSCs simultaneously fuel their stemness, cancerous and drug resistance properties. Attributes of CSCs are still not properly understood in its hypoxia niche. Addressing this, we sorted CSCs from Saos-2 (osteosarcoma) cell line using CD133 antibody. The CD133^+ve CSCs exhibited quiescent cell proliferation in DNA doubling, Ca²⁺ signaling and cell cycle analysis. CD133^+ve CSCs exhibited increased production of ATP and lactate dehydrogenase (LDH) activity under hypoxia. CD133^+ve cells exhibited decreased glucose uptake compared to ATP levels under hypoxia. Moreover, there was only negligible LDH activity in CD133^+ve cells under normoxia which do not rely on Warburg effect. Stemness markers (such as c-Myc, SOX2, Oct4 and TERT), metastasis marker (CD44) and drug resistance marker (ABCG2) were highly expressed in CD133^+ve cells. In summary, both CD133^+ve/?ve cells of Saos-2 (osteosarcoma) cell line did not exhibit Warburg effect under normoxic condition. Moreover, this significantly indicates an uncoupling between stemness and Warburg effect in CD133^+ve. This work provides a novel insight into the metabolic and functional features of CSCs in a hypoxic environment which could open new avenues for therapeutic strategies aimed to target CSCs.     

Differentiation potential of rabbit CD90-positive cells sorted from adipose-derived stem cells in vitro

To investigate the differentiation potential of purified CD90⁺ cells sorted from adipose-derived stem cells (ADSCs), CD90⁺ cells were sorted from rabbit ADSCs using flow cytometry. Then, cell expansion of CD90⁺ cells and unsorted ADSCs was observed using an inverted microscope. Furthermore, cell surface markers including CD40, CD105, and CD90 on CD90⁺ cells and unsorted ADSCs were quantified using flow cytometry. Additionally, multi-lineage differentiation ability between CD90⁺ cells and unsorted ADSCs was compared, and expression of adipocyte-related genes PPAR-r and CEBPA as well as stem cell-related gene SOX2 in CD90⁺ cells and unsorted ADSCs was determined using real-time quantitative PCR. We found that CD90⁺ cells had a stronger cell proliferation ability than unsorted ADSCs. CD90⁺ cells showed a stronger ability of osteoblast and chondrocyte differentiation than unsorted ADSCs and CD90^? cells, whereas the adipose differentiation ability of CD90⁺ cells was similar to that of ADSCs and CD90^? cells. CD14, CD105, and CD90 on CD90⁺ cells were expressed more highly than those on ADSCs. Additionally, the mRNA expression level of SOX2 in CD90⁺ cells was significantly higher than that in ADSCs, whereas the expression of PPAR-r and CEBPA was markedly lower than that in ADSCs. These results suggested that the purified CD90⁺ cells sorted from ADSCs exhibit a stronger differentiation potential than the unsorted ADSCs.     

CD98 Heavy Chain Is a Potent Positive Regulator of CD4+ T Cell Proliferation and Interferon-γ Production In Vivo

Upon their recognition of antigens presented by the MHC, T cell proliferation is vital for clonal expansion and the acquisition of effector functions, which are essential for mounting adaptive immune responses. The CD98 heavy chain (CD98hc, Slc3a2) plays a crucial role in the proliferation of both CD4⁺ and CD8⁺ T cells, although it is unclear if CD98hc directly regulates the T cell effector functions that are not linked with T cell proliferation in vivo. Here, we demonstrate that CD98hc is required for both CD4⁺ T cell proliferation and Th1 functional differentiation. T cell-specific deletion of CD98hc did not affect T cell development in the thymus. CD98hc-deficient CD4⁺ T cells proliferated in vivo more slowly as compared with control T cells. C57BL/6 mice lacking CD98hc in their CD4⁺ T cells could not control Leishmania major infections due to lowered IFN-γ production, even with massive CD4⁺ T cell proliferation. CD98hc-deficient CD4⁺ T cells exhibited lower IFN-γ production compared with wild-type T cells, even when comparing IFN-γ expression in cells that underwent the same number of cell divisions. Therefore, these data indicate that CD98hc is required for CD4⁺ T cell expansion and functional Th1 differentiation in vivo, and suggest that CD98hc might be a good target for treating Th1-mediated immune disorders.     

Prevention of lymph node metastases by adoptive transfer of CD4+ T lymphocytes admixed with irradiated tumor cells

CD4⁺8^– T lymphocytes with potent antitumor activity in vivo were obtained in peritoneal exudate cells by immunizing mice with irradiated MM48 tumor cells admixed with OK-432. These immune CD4⁺ T cells were used in adoptive immunotherapy for prevention of lymph node metastases after removal of the primary tumor. Complete cure of metastases was obtained by adoptive transfer of CD4⁺ T cells admixed with irradiated MM48 tumor cells, but not by CD4⁺ T cells alone. To analyze the curative effect of admixing tumor cells on the prevention of metastases, a model of 1-day tumor inoculated with macrophages was used. Administration of immune CD4⁺ T cells alone resulted in the regression of local tumor in more than half of the mice, although all of them eventually died of lymph node metastases. On the other hand, adoptive transfer of immune CD4⁺ T cells plus irradiated tumor cells resulted in the complete regression of local tumors in all the mice, which survived without any sign of metastasis. The curative effect of the immune CD4⁺ T cells obtained by admixing irradiated tumor cells was tumor-specific. Macrophages induced by OK-432 (tumoricidal), implanted together with tumor, assisted tumor regression more than did macrophages elicited by proteose peptone (nontumoricidal) in the same adoptive transfer system. Administration of recombinant interleukin-2 instead of stimulant tumor cells did not enhance, but rather eliminated the constitutive antitumor activity of CD4⁺ T cells. On the other hand, exogenous recombinant interleukin-1 was more effective in the enhancement of antitumor activity of the CD4⁺ T cells as compared with stimulant tumor cell administration. In this case, the activating states of macrophages at the implanted tumor site had no influence on the therapeutic efficacy. A possible role of macrophages for induction of tumor-specific cytotoxic T cells that were mediated by tumor-specific CD4⁺ T cells is discussed.     

Response to Stress in Early Tumor Colonization Modulates Switching of CD133-Positive and CD133-Negative Subpopulations in a Human Metastatic Colon Cancer Cell Line,SW620

According to the cancer stem cell (CSC) model, higher CD133 expression in tumor tissue is associated with metastasis and poor prognosis in colon cancer. As such, the CD133-positive (CD133⁺) subpopulation of cancer cells is believed to play a central role in tumor development and metastatic progression. Although CD133⁺ cells are believed to display more CSC-like behavior and be solely responsible for tumor colonization, recent research indicates that CD133⁻ cells from metastatic colon tumors not only also possess colonization capacity but also promote the growth of larger tumors in a mouse model than CD133⁺ cells, suggesting that an alternative mechanism of metastasis exists. This study investigated this possibility by examining the cell viability, tumorigenicity, and proliferation and growth capacity of the CD133⁺ and CD133⁻ subpopulations of the SW620 cell line, a human metastatic colon cancer cell line, in both an in vitro cell model and an in vivo mouse model. While both SW620 ^CD133− and SW620^CD133+ cells were found to engage in bidirectional cell-type switching in reaction to exposure to environmental stressors, including hypoxia, a cell adhesion-free environment, and extracellular matrix stimulation, both in vitro and in vivo, CD133⁻ cells were found to have a growth advantage during early colonization due to their greater resistance to proliferation inhibition. Based on these findings, a hypothetical model in which colon cancer cells engage in cell-type switching in reaction to exposure to environmental stressors is proposed. Such switching may provide a survival advantage during early colonization, as well as that explain previous conflicting observations.     

Enhanced radiosensitivity and radiation-induced apoptosis in glioma CD133-positive cells by knockdown of SirT1 expression

CD133-expressing glioma cells play a critical role in tumor recovery after treatment and are resistant to radiotherapy. Herein, we demonstrated that glioblastoma-derived CD133-positive cells (GBM-CD133⁺) are capable of self-renewal and express high levels of embryonic stem cell genes and SirT1 compared to GBM-CD133⁻ cells. To evaluate the role of SirT1 in GBM-CD133⁺, we used a lentiviral vector expressing shRNA to knock-down SirT1 expression (sh-SirT1) in GBM-CD133⁺. Silencing of SirT1 significantly enhanced the sensitivity of GBM-CD133⁺ to radiation and increased the level of radiation-mediated apoptosis. Importantly, knock-down of SirT1 increased the effectiveness of radiotherapy in the inhibition of tumor growth in nude mice transplanted with GBM-CD133⁺. Kaplan-Meier survival analysis indicated that the mean survival rate of GBM-CD133⁺ mice treated with radiotherapy was significantly improved by Sh-SirT1 as well. In sum, these results suggest that SirT1 is a potential target for increasing the sensitivity of GBM and glioblastoma-associated cancer stem cells to radiotherapy.     

Early expression of stem cell-associated genes within the CD8 compartment after treatment with a tumor vaccine

Using a mouse neuroblastoma cell line, we have demonstrated that vaccination of tumor-free mice with a cell-based vaccine leads to productive immunity and resistance to tumor challenge, while vaccination of tumor-bearing mice does not. The T cell immunity induced by this vaccine, as measured by in vitro assays, is amplified by the depletion of Treg. Our goal is to understand this barrier to the development of protective cellular immunity. mRNA microarray analyses of CD8⁺ T cells from naïve or tumor-bearing mice undergoing vaccination were carried out with or without administering anti-CD25 antibody. Gene-expression pathway analysis revealed the presence of CD8⁺ T cells expressing stem cell-associated genes early after induction of productive anti-tumor immunity in tumor-free mice, prior to any phenotypic changes, but not in tumor-bearing mice. These data demonstrate that early after the induction of productive immune response, cells within the CD8⁺ T cell compartment adopt a stem cell-related genetic phenotype that correlates with increased anti-tumor function.     

Simultaneous color‐coded imaging to distinguish cancer “stem‐like” and non‐stem cells in the same tumor

In this study, we demonstrate that the differential behavior, including malignancy and chemosensitivity, of cancer stem‐like and non‐stem cells can be simultaneously distinguished in the same tumor in real time by color‐coded imaging. CD133⁺ Huh‐7 human hepatocellular carcinoma (HCC) cells were considered as cancer stem‐like cells (CSCs), and CD133^? Huh‐7 cells were considered as non‐stem cancer cells (NSCCs). CD133⁺ cells were isolated by magnetic bead sorting after Huh‐7 cells were genetically labeled with green fluorescent protein (GFP) or red fluorescent protein (RFP). In this scheme, CD133⁺ cells were labeled with GFP and CD133^? cells were labeled with RFP. CSCs had higher proliferative potential compared to NSCCs in vitro. The same number of GFP CSCs and the RFP NSCCs were mixed and injected subcutaneously or in the spleen of nude mice. CSCs were highly tumorigenic and metastatic as well as highly resistant to chemotherapy in vivo compared to NSCCs. The ability to specifically distinguish stem‐like cancer cells in vivo in real time provides a visual target for prevention of metastasis and drug resistance. J. Cell. Biochem. 111: 1035–1041, 2010. © 2010 Wiley‐Liss, Inc.     

Development and characterization of cancer stem cell-based tumoroids as an osteosarcoma model

Three-dimensional (3D) cancer tumor models are becoming vital approaches for high-throughput drug screening, drug targeting, development of novel theranostic systems, and personalized medicine. Yet, it is becoming more evident that the tumor progression and metastasis is fueled by a subpopulation of stem-like cells within the tumor that are also called cancer stem cells (CSCs). This study aimed to develop a tumoroid model using CSCs. For this purpose CD133⁺ cells were isolated from SaOS-2 osteosarcoma cell line with magnetic-activated cell sorting. To evaluate tumoroid formation ability, the cells were incubated in different cell numbers in agar gels produced by 3D Petri Dish® method. Subsequently, CD133⁺ cells and CD133⁻ cells were co-cultured to investigate CD133⁺ cell localization in tumoroids. The characterization of tumoroids was performed using Live&Dead staining, immunohistochemistry, and quantitative polymerase chain reaction analysis. The results showed that, CD133⁺, CD133⁻ and SaOS-2 cells were all able to form 3D tumoroids regardless of the initial cell number, but, while 72 hr were needed for CD133⁺ cells to self-assemble, 24 hr were enough for CD133⁻ and SaOS-2 cells. CD133⁺ cells were located within tumoroids randomly with high cell viability. Finally, when compared to two-dimensional (2D) cultures, there were 5.88, 4.14, 6.95, and 1.68-fold higher messenger RNA expressions for Sox2, OCT3/4, Nanog, and Nestin, respectively, in CD133⁺ cells that were cultured within 3D tumoroids, showing longer maintenance of stem cell phenotype in 3D, that can allow more relevant screening and targeting efficiency in pharmaceutical testing. It was concluded that CSC-based tumoroids are propitious as 3D tumor models to fill the gap between conventional 2D in vitro culture and in vivo animal experiments for cancer research.     

Partition behavior of CD133+ stem cells from human umbilical cord blood in aqueous two‐phase systems: In route to establish novel stem cell primary recovery strategies

Aqueous two‐phase systems (ATPS) represent a promising strategy for the recovery of CD133⁺ stem cells. This particular type of stem cells has great potential for research and clinical applications. Traditional [polyethylene glycol (PEG), dextran (DEX), and ficoll] and novel (Ucon) polymer–polymer ATPS were exploited to study the partitioning behavior of CD133⁺ stem cells and contaminants from human umbilical cord blood (HUCB). The aim of the study was to select conditions under which the product of interest and the contaminants concentrate in opposite phases. To accomplish this, three independent samples were tested: (1) enriched CD133⁺ sample, (2) whole HUCB (contaminants), and (3) complex sample (CD133⁺ stem cells and contaminants). The objective of this research was to evaluate the partition behavior of CD133⁺ in ATPS in route to establish the basis for the development of a novel and scalable purification bioprocess. In conclusion, the partitioning behavior of CD133⁺ stem cells and contaminants from complex samples was as follows: 59% of CD133⁺ stem cells fractionated to the top phase when employing ficoll 400,000–DEX 70,000 or 100% to the bottom phase with Ucon‐DEX 75,000 and PEG 8,000‐DEX 500,000 ATPS. In average, 35% of the contaminants partitioned to the top phase of the ficoll 400,000‐DEX 70,000 ATPS, 99% to the dextran rich phase of the Ucon‐DEX 75,000 systems and 97% to the bottom phase of the PEG 8,000‐DEX 500,000. Cell viability was at least 98% after ATPS recovery. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:700–707, 2014     

Wnt/β-catenin Signaling Inhibitors suppress the Tumor-initiating properties of a CD44+CD133+ subpopulation of Caco-2 cells

Tumor-initiating cells or cancer stem cells are a subset of cancer cells that have tumorigenic potential in human cancer. Although several markers have been proposed to distinguish tumor-initiating cells from colorectal cancer cells, little is known about how this subpopulation contributes to tumorigenesis. Here, we characterized a tumor-initiating cell subpopulation from Caco-2 colorectal cancer cells. Based on the findings that Caco-2 cell subpopulations express different cell surface markers, we were able to discriminate three main fractions, CD44^-CD133^-, CD44^-CD133⁺, and CD44⁺CD133⁺ subsets, and characterized their biochemical and tumorigenic properties. Our results show that CD44⁺CD133⁺ cells possessed an unusual capacity to proliferate and could form tumors when transplanted into NSG mice. Additionally, primary tumors grown from CD44⁺CD133⁺ Caco-2 cells contained mixed populations of CD44⁺CD133⁺ and non-CD44⁺CD133⁺ Caco-2 cells, indicating that the full phenotypic heterogeneity of the parental Caco-2 cells was re-created. Notably, only the CD44⁺CD133⁺ subset of Caco-2-derived primary tumors had tumorigenic potential in NSG mice, and the tumor growth of CD44⁺CD133⁺ cells was faster in secondary xenografts than in primary transplants. Gene expression analysis revealed that the Wnt/β-catenin pathway was over-activated in CD44⁺CD133⁺ cells, and the growth and tumorigenic potential of this subpopulation were significantly suppressed by small-molecule Wnt/β-catenin signaling inhibitors. Our findings suggest that the CD44⁺CD133⁺ subpopulation from Caco-2 cells was highly enriched in tumorigenic cells and will be useful for investigating the mechanisms leading to human colorectal cancer development.     

Prominin 1/CD133 Endothelium Sustains Growth of Proneural Glioma

In glioblastoma high expression of the CD133 gene, also called Prominin1, is associated with poor prognosis. The PDGF-driven proneural group represents a subset of glioblastoma in which CD133 is not overexpressed. Interestingly, this particular subset shows a relatively good prognosis. As with many other tumors, gliobastoma is believed to arise and be maintained by a restricted population of stem-like cancer cells that express the CD133 transmembrane protein. The significance of CD133⁺ cells for gliomagenesis is controversial because of conflicting supporting evidence. Contributing to this inconsistency is the fact that the isolation of CD133⁺ cells has largely relied on the use of antibodies against ill-defined glycosylated epitopes of CD133. To overcome this problem, we used a knock-in lacZ reporter mouse, Prom1^lacZ/+, to track Prom1⁺ cells in the brain. We found that Prom1 (prominin1, murine CD133 homologue) is expressed by cells that express markers characteristic of the neuronal, glial or vascular lineages. In proneural tumors derived from injection of RCAS-PDGF into the brains of tv-a;Ink4a-Arf^−/− Prom1^lacZ/+ mice, Prom1⁺ cells expressed markers for astrocytes or endothelial cells. Mice co-transplanted with proneural tumor sphere cells and Prom1⁺ endothelium had a significantly increased tumor burden and more vascular proliferation (angiogenesis) than those co-transplanted with Prom1⁻ endothelium. We also identified specific genes in Prom1⁺ endothelium that code for endothelial signaling modulators that were not overexpressed in Prom1⁻ endothelium. These factors may support proneural tumor progression and could be potential targets for anti-angiogenic therapy.     

Rapid G0/1 transition and cell cycle progression in CD8+ T cells compared to CD4+ T cells following in vitro stimulation

T‐cell population consists of two major subsets, CD4⁺ T cells and CD8⁺ T cells, which can be distinguished by the expression of CD4 or CD8 molecules, respectively. Although they play quite different roles in the immune system, many of their basic cellular processes such as proliferation following stimulation are presumably common. In this study, we have carefully analyzed time–course of G0/1 transition as well as cell cycle progression in the two subsets of quiescent T‐cell population following in vitro growth stimulation. We found that CD8⁺ T cells promote G0/1 transition more rapidly and drive their cell cycle progression faster compared to CD4⁺ T cells. In addition, expression of CD25 and effects of its blockade revealed that IL‐2 is implicated in the rapid progression, but not the earlier G0/1 transition, of CD8⁺ T cells.