Malignant gliomas are aggressive brain tumors with limited therapeutic options, and improvements in treatment require a deeper molecular understanding of this disease. As in other cancers, recent ...studies have identified highly tumorigenic subpopulations within malignant gliomas, known generally as cancer stem cells. Here, we demonstrate that glioma stem cells (GSCs) produce nitric oxide via elevated nitric oxide synthase-2 (NOS2) expression. GSCs depend on NOS2 activity for growth and tumorigenicity, distinguishing them from non-GSCs and normal neural progenitors. Gene expression profiling identified many
NOS2-regulated genes, including the cell-cycle inhibitor cell division autoantigen-1 (
CDA1). Further, high
NOS2 expression correlates with decreased survival in human glioma patients, and NOS2 inhibition slows glioma growth in a murine intracranial model. These data provide insight into how GSCs are mechanistically distinct from their less tumorigenic counterparts and suggest that NOS2 inhibition may be an efficacious approach to treating this devastating disease.
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► Glioma stem cell proliferation is supported by nitric oxide synthase-2 (NOS2) ► Nonstem glioma cells and normal neural stem cells are not dependent on NOS2 ► NOS2 affects glioma stem cell gene expression, including cell-cycle inhibitor CDA1 ► Pharmacological inhibition of NOS2 attenuates glioma growth in vivo
Glioblastomas are the most common and most lethal primary brain tumor. Recent studies implicate an important role for a restricted population of neoplastic cells (glioma stem cells (GSCs)) in glioma ...maintenance and recurrence. We now demonstrate that GSCs preferentially express two interleukin 6 (IL6) receptors: IL6 receptor alpha (IL6Rα) and glycoprotein 130 (gp130). Targeting IL6Rα or IL6 ligand expression in GSCs with the use of short hairpin RNAs (shRNAs) significantly reduces growth and neurosphere formation capacity while increasing apoptosis. Perturbation of IL6 signaling in GSCs attenuates signal transducers and activators of transcription three (STAT3) activation, and small molecule inhibitors of STAT3 potently induce GSC apoptosis. These data indicate that STAT3 is a downstream mediator of prosurvival IL6 signals in GSCs. Targeting of IL6Rα or IL6 expression in GSCs increases the survival of mice bearing intracranial human glioma xenografts. IL6 is clinically significant because elevated IL6 ligand and receptor expression are associated with poor glioma patient survival. The potential utility of anti‐IL6 therapies is demonstrated by decreased growth of subcutaneous human GSC‐derived xenografts treated with IL6 antibody. Together, our data indicate that IL6 signaling contributes to glioma malignancy through the promotion of GSC growth and survival, and that targeting IL6 may offer benefit for glioma patients. STEM CELLS 2009;27:2393–2404
Glioblastomas display cellular hierarchies containing tumor-propagating glioblastoma stem cells (GSCs). STAT3 is a critical signaling node in GSC maintenance but molecular mechanisms underlying STAT3 ...activation in GSCs are poorly defined. Here we demonstrate that the bone marrow X-linked (BMX) nonreceptor tyrosine kinase activates STAT3 signaling to maintain self-renewal and tumorigenic potential of GSCs. BMX is differentially expressed in GSCs relative to nonstem cancer cells and neural progenitors. BMX knockdown potently inhibited STAT3 activation, expression of GSC transcription factors, and growth of GSC-derived intracranial tumors. Constitutively active STAT3 rescued the effects of BMX downregulation, supporting that BMX signals through STAT3 in GSCs. These data demonstrate that BMX represents a GSC therapeutic target and reinforces the importance of STAT3 signaling in stem-like cancer phenotypes.
► BMX is preferentially expressed in glioblastoma stem cells ► BMX activates STAT3 signaling specifically in glioblastoma stem cells ► BMX controls the expression of key glioblastoma stem cell transcription factors ► Targeting BMX disrupts tumorigenic potential of glioblastoma stem cells
Glioblastomas are deadly cancers that display a functional cellular hierarchy maintained by self-renewing glioblastoma stem cells (GSCs). GSCs are regulated by molecular pathways distinct from the ...bulk tumor that may be useful therapeutic targets. We determined that A20 (TNFAIP3), a regulator of cell survival and the NF-kappaB pathway, is overexpressed in GSCs relative to non-stem glioblastoma cells at both the mRNA and protein levels. To determine the functional significance of A20 in GSCs, we targeted A20 expression with lentiviral-mediated delivery of short hairpin RNA (shRNA). Inhibiting A20 expression decreased GSC growth and survival through mechanisms associated with decreased cell-cycle progression and decreased phosphorylation of p65/RelA. Elevated levels of A20 in GSCs contributed to apoptotic resistance: GSCs were less susceptible to TNFalpha-induced cell death than matched non-stem glioma cells, but A20 knockdown sensitized GSCs to TNFalpha-mediated apoptosis. The decreased survival of GSCs upon A20 knockdown contributed to the reduced ability of these cells to self-renew in primary and secondary neurosphere formation assays. The tumorigenic potential of GSCs was decreased with A20 targeting, resulting in increased survival of mice bearing human glioma xenografts. In silico analysis of a glioma patient genomic database indicates that A20 overexpression and amplification is inversely correlated with survival. Together these data indicate that A20 contributes to glioma maintenance through effects on the glioma stem cell subpopulation. Although inactivating mutations in A20 in lymphoma suggest A20 can act as a tumor suppressor, similar point mutations have not been identified through glioma genomic sequencing: in fact, our data suggest A20 may function as a tumor enhancer in glioma through promotion of GSC survival. A20 anticancer therapies should therefore be viewed with caution as effects will likely differ depending on the tumor type.
Cancer stem cells (CSCs) are a subpopulation of tumor cells suggested to be critical for tumor maintenance, metastasis, and therapeutic resistance. Prospective identification and targeting of CSCs ...are therefore priorities for the development of novel therapeutic paradigms. Although CSC enrichment has been achieved with cell surface proteins including CD133 (Prominin-1), the roles of current CSC markers in tumor maintenance remain unclear. We examined the glioblastoma stem cell (GSC) perivascular microenvironment in patient specimens to identify enrichment markers with a functional significance and identified integrin α6 as a candidate. Integrin α6 is coexpressed with conventional GSC markers and enriches for GSCs. Targeting integrin α6 in GSCs inhibits self-renewal, proliferation, and tumor formation capacity. Our results provide evidence that GSCs express high levels of integrin α6, which can serve not only as an enrichment marker but also as a promising antiglioblastoma therapy.
► Integrin α6 marks glioblastoma cells in the perivascular niche ► Integrin α6 selection enriches for glioblastoma stem cells ► Tumor cells with high integrin α6 expression are highly tumorigenic ► Targeting integrin α6 attenuates glioblastoma stem cell growth
Nontyphoidal Salmonella (NTS) invasive infections are an important cause of morbidity and mortality in sub-Saharan Africa. Several vaccines are in development to prevent these infections. We describe ...an NTS opsonophagocytic killing assay that uses HL-60 cells and baby rabbit complement to quantify functional antibodies elicited by candidate NTS vaccines.
Glioblastomas are deadly cancers that display a functional cellular hierarchy maintained by self-renewing glioblastoma stem cells (GSCs). GSCs are regulated by molecular pathways distinct from the ...bulk tumor that may be useful therapeutic targets. We determined that A20 (TNFAIP3), a regulator of cell survival and the NF-κB pathway, is overexpressed in GSCs relative to non-stem glioblastoma cells at both the mRNA and protein levels. To determine the functional significance of A20 in GSCs, we targeted A20 expression with lentiviral-mediated delivery of short hairpin RNA (shRNA). Inhibiting A20 expression decreased GSC growth and survival through mechanisms associated with decreased cell-cycle progression and decreased phosphorylation of p65/RelA. Elevated levels of A20 in GSCs contributed to apoptotic resistance: GSCs were less susceptible to TNFα-induced cell death than matched non-stem glioma cells, but A20 knockdown sensitized GSCs to TNFα-mediated apoptosis. The decreased survival of GSCs upon A20 knockdown contributed to the reduced ability of these cells to self-renew in primary and secondary neurosphere formation assays. The tumorigenic potential of GSCs was decreased with A20 targeting, resulting in increased survival of mice bearing human glioma xenografts. In silico analysis of a glioma patient genomic database indicates that A20 overexpression and amplification is inversely correlated with survival. Together these data indicate that A20 contributes to glioma maintenance through effects on the glioma stem cell subpopulation. Although inactivating mutations in A20 in lymphoma suggest A20 can act as a tumor suppressor, similar point mutations have not been identified through glioma genomic sequencing: in fact, our data suggest A20 may function as a tumor enhancer in glioma through promotion of GSC survival. A20 anticancer therapies should therefore be viewed with caution as effects will likely differ depending on the tumor type.
Abstract
Although current therapeutic strategies for malignant gliomas are non-specifically directed against the tumor bulk, increasing evidence suggests that a single glioma contains a range of ...phenotypically disparate cell populations with differential capacity for tumor maintenance and initiation. Recent work in brain tumors suggests the existence of cellular sub-populations (known as cancer stem cells, or CSCs) that possess stem cell-like behaviors and a potent capacity for tumor initiation in transplantation assays relative to non-CSCs. Specifically targeting the highly tumorigenic CSCs has the potential to improve the prognosis of malignant glioma patients, but many molecularly-directed anti-CSC agents may also compromise the survival of normal neural stem cells due to molecular similarities between CSCs and normal stem cells. Here we demonstrate that malignant glioma CSCs express high levels of a particular protein relative to non-CSCs. Glioma CSC growth and tumorigenic capacity were abrogated by multiple strategies interfering with the expression and activity of this protein, including RNA interference, pharmacological inhibition, and heterologous expression of a prokaryotic enzyme that specifically consumes the enzymatic product of this critical protein. Importantly, tumor growth was inhibited by systemic treatment of xenograft-bearing mice with a well-studied small molecule inhibitor of this protein that has already demonstrated low toxicity in clinical trials for other diseases. Though the activity of this protein appears critical for the maintenance of highly tumorigenic glioma CSCs, our examination of both normal human neural progenitor cells and neural stem cells derived from genetically disrupted mice indicate no substantial role for this protein in normal neural stem cells. Our findings identify a novel glioma therapeutic target with a negligible role in normal neural stem cells, suggesting clinical utility for selective inhibitors of this CSC-specific molecular target.
Citation Format: {Authors}. {Abstract title} abstract. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3318.
Glioblastomas display cellular hierarchies containing tumor-propagating glioblastoma stem cells (GSCs). STAT3 is a critical signaling node in GSC maintenance but molecular mechanisms underlying STAT3 ...activation in GSCs are poorly defined. Here we demonstrate that the non-receptor tyrosine kinase BMX activates STAT3 signaling to maintain self-renewal and tumorigenic potential of GSCs. BMX is differentially expressed in GSCs relative to non-stem cancer cells and neural progenitors. BMX knockdown potently inhibited STAT3 activation, expression of GSC transcription factors, and growth of GSC-derived intracranial tumors. Constitutively active STAT3 rescued the effects of BMX downregulation, supporting that BMX signals through STAT3 in GSCs. These data demonstrate that BMX represents a GSC therapeutic target and reinforces the importance of STAT3 signaling in stem-like cancer phenotypes.
The Cancer Stem Cell Paradigm Eyler, Christine E.; Heddleston, John M.; Hitomi, Masahiro ...
Adult Stem Cells
Book Chapter
Following the discovery that leukemic cells exhibit properties of hematopoietic stem cells, the prospective isolation of stem-like cells with high tumorigenicity has been reported for a variety of ...tumors. These “cancer stem cells” (CSCs) are so named because they exhibit the capacity for sustained self-renewal and possess the ability to regenerate transplanted tumor masses resembling the primary tumor in immunodeficient mice. However, the existence of CSCs remains contentious in the field of cancer biology, in part because of the application of inconsistent and inaccurate definitions and disputes over terminology. Herein, we review the discovery of CSCs, examine in detail their physical and functional characteristics, the mechanisms that lead to their formation, and how their contribution to solid tumor formation impacts cancer therapies.
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