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Ismail F, Winkler DA. Getting to the Source: Selective Drug Targeting of Cancer Stem Cells. ChemMedChem 2014; 9:885-98. [DOI: 10.1002/cmdc.201400068] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 04/02/2014] [Indexed: 12/22/2022]
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Xie J, Ma YH, Wan M, Zhan RY, Zhou YQ. Expression of dedifferentiation markers and multilineage markers in U251 glioblastoma cells with silenced EGFR and FGFR genes. Oncol Lett 2013; 7:131-136. [PMID: 24348834 PMCID: PMC3861577 DOI: 10.3892/ol.2013.1685] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 10/31/2013] [Indexed: 11/22/2022] Open
Abstract
Epithelial growth factor (EGF) and basic fibroblast growth factor (bFGF), and their receptors, epithelial growth factor receptor (EGFR) and bFGF receptor (bFGFR), are frequently overexpressed in high-grade gliomas. In the present study, the EGF and bFGF levels in U251 glioblastoma cell culture supernatants were determined by ELISA, and enhanced green fluorescent protein (EGFP)-labeled recombinant lentiviral expression vectors with small interfering RNA targeting the EGFR and bFGFR genes were constructed. The mRNA expression levels of EGFR, bFGFR, cluster of differentiation (CD)133, glial fibrillary acidic protein (GFAP), tubulin-β3 (TUBB3) and myelin basic protein (MBP) were determined using quantitative polymerase chain reactions in U251 cells prior to and following silencing of the EGFR and/or bFGFR genes. Prior to silencing, the U251 cells secreted EGF and bFGF, and expressed EGFR, bFGFR, CD133, GFAP, TUBB3 and MBP mRNA. Subsequent to silencing the EGFR and/or bFGFR gene, CD133 mRNA expression decreased and GFAP and TUBB3 mRNA expression increased. Silencing the EGFR and FGFR genes acted synergistically to downregulate CD133 expression. The downregulation of CD133 mRNA expression and the upregulation of GFAP and TUBB3 mRNA expression were not significantly different when blocking the EGFR and FGFR pathways. These results indicate that autocrine or paracrine EGF and/or FGF mechanisms exist in U251 cells. Knocking down the EGFR and/or FGFR genes downregulates CD133 mRNA expression and facilitates glial and neuronal differentiation in U251 cells.
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Affiliation(s)
- Jue Xie
- Department of Blood Transfusion, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
| | - Yue-Hui Ma
- Department of Neurosurgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
| | - Ming Wan
- Department of Neurosurgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
| | - Ren-Ya Zhan
- Department of Neurosurgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
| | - Yong-Qing Zhou
- Department of Neurosurgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang 310003, P.R. China
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Genome stability pathways in head and neck cancers. Int J Genomics 2013; 2013:464720. [PMID: 24364026 PMCID: PMC3834617 DOI: 10.1155/2013/464720] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 09/19/2013] [Accepted: 09/20/2013] [Indexed: 12/12/2022] Open
Abstract
Genomic instability underlies the transformation of host cells toward malignancy, promotes development of invasion and metastasis and shapes the response of established cancer to treatment. In this review, we discuss recent advances in our understanding of genomic stability in squamous cell carcinoma of the head and neck (HNSCC), with an emphasis on DNA repair pathways. HNSCC is characterized by distinct profiles in genome stability between similarly staged cancers that are reflected in risk, treatment response and outcomes. Defective DNA repair generates chromosomal derangement that can cause subsequent alterations in gene expression, and is a hallmark of progression toward carcinoma. Variable functionality of an increasing spectrum of repair gene polymorphisms is associated with increased cancer risk, while aetiological factors such as human papillomavirus, tobacco and alcohol induce significantly different behaviour in induced malignancy, underpinned by differences in genomic stability. Targeted inhibition of signalling receptors has proven to be a clinically-validated therapy, and protein expression of other DNA repair and signalling molecules associated with cancer behaviour could potentially provide a more refined clinical model for prognosis and treatment prediction. Development and expansion of current genomic stability models is furthering our understanding of HNSCC pathophysiology and uncovering new, promising treatment strategies.
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Wang ML, Chiou SH, Wu CW. Targeting cancer stem cells: emerging role of Nanog transcription factor. Onco Targets Ther 2013; 6:1207-20. [PMID: 24043946 PMCID: PMC3772775 DOI: 10.2147/ott.s38114] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The involvement of stemness factors in cancer initiation and progression has drawn much attention recently, especially after the finding that introducing four stemness factors in somatic cells is able to reprogram the cells back to an embryonic stem cell-like state. Following accumulating data revealing abnormal elevated expression levels of key stemness factors, like Nanog, Oct4, and Sox2, in several types of cancer stem cells; the importance and therapeutic potential of targeting these stemness regulators in cancers has turned to research focus. Nanog determines cell fate in both embryonic and cancer stem cells; activating Nanog at an inappropriate time would result in cancer stem cells rather than normal pluripotent stem cells or differentiated somatic cells. Upregulated Nanog is correlated with poor survival outcome of patients with various types of cancer. The discoveries of downstream regulatory pathways directly or indirectly mediated by Nanog indicate that Nanog regulates several aspects of cancer development such as tumor cell proliferation, self-renewal, motility, epithelial-mesenchymal transition, immune evasion, and drug-resistance, which are all defined features for cancer stem cells. The current review paper illustrates the central role of Nanog in the regulatory networks of cancer malignant development and stemness acquirement, as well as in the communication between cancer cells and the surrounding stroma. Though a more defined model is needed to test the therapeutic efficacy of targeting Nanog as a cancer treatment method, current animal experiments using siNanog or shNanog have shown the promising therapeutic potential of Nanog targeting in several types of cancer.
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Affiliation(s)
- Mong-Lien Wang
- Institute of Biochemistry and Molecular Biology, National Yang Ming University, Taipei, Taiwan
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Adams A, Warner K, Nör JE. Salivary gland cancer stem cells. Oral Oncol 2013; 49:845-853. [PMID: 23810400 DOI: 10.1016/j.oraloncology.2013.05.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 05/22/2013] [Accepted: 05/31/2013] [Indexed: 12/13/2022]
Abstract
Emerging evidence suggests the existence of a tumorigenic population of cancer cells that demonstrate stem cell-like properties such as self-renewal and multipotency. These cells, termed cancer stem cells (CSC), are able to both initiate and maintain tumor formation and progression. Studies have shown that CSC are resistant to traditional chemotherapy treatments preventing complete eradication of the tumor cell population. Following treatment, CSC are able to re-initiate tumor growth leading to patient relapse. Salivary gland cancers are relatively rare but constitute a highly significant public health issue due to the lack of effective treatments. In particular, patients with mucoepidermoid carcinoma or adenoid cystic carcinoma, the two most common salivary malignancies, have low long-term survival rates due to the lack of response to current therapies. Considering the role of CSC in resistance to therapy in other tumor types, it is possible that this unique sub-population of cells is involved in resistance of salivary gland tumors to treatment. Characterization of CSC can lead to better understanding of the pathobiology of salivary gland malignancies as well as to the development of more effective therapies. Here, we make a brief overview of the state-of-the-science in salivary gland cancer, and discuss possible implications of the cancer stem cell hypothesis to the treatment of salivary gland malignancies.
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Affiliation(s)
- April Adams
- Department of Restorative Sciences, University of Michigan School of Dentistry, United States
| | - Kristy Warner
- Department of Restorative Sciences, University of Michigan School of Dentistry, United States
| | - Jacques E Nör
- Department of Restorative Sciences, University of Michigan School of Dentistry, United States; Department of Biomedical Engineering, University of Michigan College of Engineering, United States; Department of Otolaryngology, University of Michigan School of Medicine, United States.
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Ripamonti F, Albano L, Rossini A, Borrelli S, Fabris S, Mantovani R, Neri A, Balsari A, Magnifico A, Tagliabue E. EGFR through STAT3 modulates ΔN63α expression to sustain tumor-initiating cell proliferation in squamous cell carcinomas. J Cell Physiol 2013; 228:871-8. [PMID: 23018838 DOI: 10.1002/jcp.24238] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 09/24/2012] [Indexed: 01/01/2023]
Abstract
Many squamous cell carcinomas (SCCs) are characterized by high levels of EGFR and by overexpression of the ΔNp63α isoform. Here, we investigated the regulation of ΔNp63α expression upon EGFR activation and the role of the EGFR-ΔNp63α axis in proliferation of SCC tumor-initiating cells (TICs). SCC cell lines A-431, Cal-27, and SCC-25 treated with EGF showed a time-dependent increase in ΔNp63α expression at the protein and mRNA levels, which was blocked by the tyrosine kinase inhibitor (TKI) Lapatinib. RNA interference experiments suggested the role of STAT3 in regulating ΔNp63α expression downstream of EGFR. Inactivation of EGFR by the monoclonal antibody Cetuximab and RNA interference against STAT3 or ΔNp63α impaired the TICs ability to grow under non-differentiating conditions. Radiation treatment, which triggers EGFR activation, induced ΔNp63α accumulation without affecting TICs proliferation, whereas the combination Cetuximab plus radiation significantly reduced TICs growth under non-differentiating conditions. Together, our findings provide evidence that ΔNp63α expression is regulated by EGFR activation through STAT3 and that the EGFR-ΔNp63α axis is crucial for proliferation of TICs present in SCCs.
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Affiliation(s)
- Francesca Ripamonti
- Molecular Targeting Unit, Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy
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LRIG1 modulates aggressiveness of head and neck cancers by regulating EGFR-MAPK-SPHK1 signaling and extracellular matrix remodeling. Oncogene 2013; 33:1375-84. [PMID: 23624915 DOI: 10.1038/onc.2013.98] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 01/29/2013] [Accepted: 02/01/2013] [Indexed: 12/20/2022]
Abstract
EGFR overexpression and chromosome 3p deletion are two frequent events in head and neck cancers. We previously mapped the smallest region of recurrent copy-number loss at 3p12.2-p14.1. LRIG1, a negative regulator of EGFR, was found at 3p14, and its copy-number loss correlated with poor clinical outcome. Inducible expression of LRIG1 in head and neck cancer TW01 cells, a line with low LRIG1 levels, suppressed cell proliferation in vitro and tumor growth in vivo. Gene expression profiling, quantitative RT-PCR, chromatin immunoprecipitation, and western blot analysis demonstrated that LRIG1 modulated extracellular matrix (ECM) remodeling and EGFR-MAPK-SPHK1 transduction pathway by suppressing expression of EGFR ligands/activators, MMPs and SPHK1. In addition, LRIG1 induction triggered cell morphology changes and integrin inactivation, which coupled with reduced SNAI2 expression. By contrast, knockdown of endogenous LRIG1 in TW06 cells, a line with normal LRIG1 levels, significantly enhanced cell proliferation, migration and invasiveness. Such tumor-promoting effects could be abolished by specific MAPK or SPHK1 inhibitors. Our data suggest LRIG1 as a tumor suppressor for head and neck cancers; LRIG1 downregulation in cancer cells enhances EGFR-MAPK-SPHK1 signaling and ECM remodeling activity, leading to malignant phenotypes of head and neck cancers.
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Perez R, Crombet T, de Leon J, Moreno E. A view on EGFR-targeted therapies from the oncogene-addiction perspective. Front Pharmacol 2013; 4:53. [PMID: 23637683 PMCID: PMC3636470 DOI: 10.3389/fphar.2013.00053] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 04/04/2013] [Indexed: 12/28/2022] Open
Abstract
Tumor cell growth and survival can often be impaired by inactivating a single oncogen– a phenomenon that has been called as “oncogene addiction.” It is in such scenarios that molecular targeted therapies may succeed. among known oncogenes, the epidermal growth factor receptor (EGFR) has become the target of different cancer therapies. So far, however, the clinical benefit from EGFR-targeted therapies has been rather limited. a critical review of the large amount of clinical data obtained with anti-EGFR agents, carried out from the perspective of the oncogene addiction concept, may help to understand the causes of the unsatisfactory results. In this article we intend to do such an exercise taking as basis for the analysis a few case studies of anti-EGFR agents that are currently in the clinic. There, the “EGFR addiction” phenomenon becomes apparent in high-responder patients. We further discuss how the concept of oncogene addiction needs to be interpreted on the light of emerging experimental evidences and ideas; in particular, that EGFR addiction may reflect the interconnection of several cellular pathways. In this regard we set forth several hypotheses; namely, that requirement of higher glucose uptake by hypoxic tumor cells may reinforce EGFR addiction; and that chronic use of EGFR-targeted antibodies in EGFR-addicted tumors would induce stable disease by reversing the malignant phenotype of cancer stem cells and also by sustaining an anti-tumor T cell response. Finally, we discuss possible reasons for the failure of certain combinatorial therapies involving anti-EGFR agents, arguing that some of these agents might produce either a negative or a positive trans-modulation effect on other oncogenes. It becomes evident that we need operational definitions of EGFR addiction in order to determine which patient populations may benefit from treatment with anti-EGFR drugs, and to improve the design of these therapies.
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Affiliation(s)
- Rolando Perez
- Center of Molecular Immunology Havana, Cuba ; Biotech Pharmaceuticals Co. Ltd. Beijing, China
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Yang X, Sarvestani SK, Moeinzadeh S, He X, Jabbari E. Effect of CD44 binding peptide conjugated to an engineered inert matrix on maintenance of breast cancer stem cells and tumorsphere formation. PLoS One 2013; 8:e59147. [PMID: 23527117 PMCID: PMC3601067 DOI: 10.1371/journal.pone.0059147] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 02/11/2013] [Indexed: 01/09/2023] Open
Abstract
INTRODUCTION As cancer cells are affected by many factors in their microenvironment, a major challenge is to isolate the effect of a specific factor on cancer stem cells (CSCs) while keeping other factors unchanged. We have developed a synthetic inert 3D polyethylene glycol diacrylate (PEGDA) gel culture system as a unique tool to study the effect of microenvironmental factors on CSCs response. We have reported that CSCs formed in the inert PEGDA gel by encapsulation of breast cancer cells maintain their stemness within a certain range of gel stiffness. The objective was to investigate the effect of CD44 binding peptide (CD44BP) conjugated to the gel on the maintenance of breast CSCs. METHODS 4T1 or MCF7 breast cancer cells were encapsulated in PEGDA gel with CD44BP conjugation. Control groups included dissolved CD44BP and the gel with mutant CD44BP conjugation. Tumorsphere size and density, and expression of CSC markers were determined after 9 days. For in vivo, cell encapsulated gels were inoculated in syngeneic Balb/C mice and tumor formation was determined after 4 weeks. Effect of CD44BP conjugation on breast CSC maintenance was compared with integrin binding RGD peptide (IBP) and fibronectin-derived heparin binding peptide (FHBP). RESULTS Conjugation of CD44BP to the gel inhibited breast tumorsphere formation in vitro and in vivo. The ability of the encapsulated cells to form tumorspheres in the peptide-conjugated gels correlated with the expression of CSC markers. Tumorsphere formation in vitro was enhanced by FHBP while it was abolished by IBP. CONCLUSION CD44BP and IBP conjugated to the gel abolished tumorsphere formation by encapsulated 4T1 cells while FHBP enhanced tumorsphere formation compared to cells in the gel without peptide. The PEGDA hydrogel culture system provides a novel tool to investigate the individual effect of factors in the microenvironment on CSC maintenance without interference of other factors.
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Affiliation(s)
- Xiaoming Yang
- Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America
- Dorn Research Institute, Columbia, South Carolina, United States of America
| | - Samaneh K. Sarvestani
- Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America
| | - Seyedsina Moeinzadeh
- Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America
| | - Xuezhong He
- Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America
| | - Esmaiel Jabbari
- Biomimetic Materials and Tissue Engineering Laboratory, Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States of America
- * E-mail:
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Chen X, Chen L, Chen J, Hu W, Gao H, Xie B, Wang X, Yin Z, Li S, Wang X. ADAM17 promotes U87 glioblastoma stem cell migration and invasion. Brain Res 2013; 1538:151-8. [PMID: 23470260 DOI: 10.1016/j.brainres.2013.02.025] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 02/07/2013] [Accepted: 02/15/2013] [Indexed: 12/18/2022]
Abstract
Glioblastoma stem cells (GSCs) are thought to contribute to the diffuse invasiveness of malignant gliomas. Emerging evidence supports a role for a disintegrin and metalloproteinase 17 (ADAM17) in proteolytic ectodomain shedding of several EGFR-binding ligands, which subsequently activate PI3K/AKT and MEK/ERK pathways through EGFR phosphorylation thus mediating glioma invasiveness. However, it is not clear if ADAM17 also plays important roles in promoting GSC invasion. In this study, we isolated CD133+ GSCs from the human glioblastoma cell line U87 using fluorescence-activated cell sorting and demonstrated their increased invasive potential compared with matched non-stem tumor cells. Furthermore, we showed that CD133+ GSCs expressed higher levels of ADAM17. Immunofluorescence staining revealed that high expression levels of ADAM17 at the invasive front were correlated with the presence of CD133+ GSCs in human glioblastoma specimens. Stimulation with the ADAM17 agonist chemokine phorbol myristate acetate increased migration and invasion of GSCs, which was counteracted by ADAM17 knockdown. In addition, ADAM17 also induced CD133+ GSC invasion via activation of the EGFR/PI3K/AKT signaling pathway. These findings suggest that ADAM17 is involved in U87 GSC invasive process and may provide a potential therapeutic target for glioma treatment.
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Affiliation(s)
- Xiangrong Chen
- Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou 510282, Guangdong Province, China; Department of Neurosurgery, the Second Affiliated Hospital, Fujian Medical University, Quanzhou 362000, Fujian Province, China
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Kuo SZ, Blair KJ, Rahimy E, Kiang A, Abhold E, Fan JB, Wang-Rodriguez J, Altuna X, Ongkeko WM. Salinomycin induces cell death and differentiation in head and neck squamous cell carcinoma stem cells despite activation of epithelial-mesenchymal transition and Akt. BMC Cancer 2012; 12:556. [PMID: 23176396 PMCID: PMC3522015 DOI: 10.1186/1471-2407-12-556] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 11/21/2012] [Indexed: 01/06/2023] Open
Abstract
Background Cancer stem cells (CSC) are believed to play a crucial role in cancer recurrence due to their resistance to conventional chemotherapy and capacity for self-renewal. Recent studies have reported that salinomycin, a livestock antibiotic, selectively targets breast cancer stem cells 100-fold more effectively than paclitaxel. In our study we sought to determine the effects of salinomycin on head and neck squamous cell carcinoma (HNSCC) stem cells. Methods MTS and TUNEL assays were used to study cell proliferation and apoptosis as a function of salinomycin exposure in JLO-1, a putative HNSCC stem cell culture. MTS and trypan blue dye exclusion assays were performed to investigate potential drug interactions between salinomycin and cisplatin or paclitaxel. Stem cell-like phenotype was measured by mRNA expression of stem cell markers, sphere-forming capacity, and matrigel invasion assays. Immunoblotting was also used to determine expression of epithelial-mesenchymal transition (EMT) markers and Akt phosphorylation. Arrays by Illumina, Inc. were used to profile microRNA expression as a function of salinomycin dose. Results In putative HNSCC stem cells, salinomycin was found to significantly inhibit cell viability, induce a 71.5% increase in levels of apoptosis, elevate the Bax/Bcl-2 ratio, and work synergistically with cisplatin and paclitaxel in inducing cell death. It was observed that salinomycin significantly inhibited sphere forming-capability and repressed the expression of CD44 and BMI-1 by 3.2-fold and 6.2-fold, respectively. Furthermore, salinomycin reduced invasion of HNSCC stem cells by 2.1 fold. Contrary to expectations, salinomycin induced the expression of EMT markers Snail, vimentin, and Zeb-1, decreased expression of E-cadherin, and also induced phosphorylation of Akt and its downstream targets GSK3-β and mTOR. Conclusions These results demonstrate that in HNSCC cancer stem cells, salinomycin can cause cell death and decrease stem cell properties despite activation of both EMT and Akt.
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Affiliation(s)
- Selena Z Kuo
- Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of California, San Diego, San Diego, CA, USA
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Feng Y, Dai X, Li X, Wang H, Liu J, Zhang J, Du Y, Xia L. EGF signalling pathway regulates colon cancer stem cell proliferation and apoptosis. Cell Prolif 2012; 45:413-9. [PMID: 22925500 DOI: 10.1111/j.1365-2184.2012.00837.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
OBJECTIVES Cancer stem cells (CSCs) compose a subpopulation of cells within a tumour that can self-renew and proliferate. Growth factors such as epidermal growth factor (EGF) and basic fibroblast growth factor (b-FGF) promote cancer stem cell proliferation in many solid tumours. This study assesses whether EGF, bFGF and IGF signalling pathways are essential for colon CSC proliferation and self-renewal. MATERIAL AND METHODS Colon CSCs were cultured in serum-free medium (SFM) with one of the following growth factors: EGF, bFGF or IGF. Characteristics of CSC gene expression were evaluated by real time PCR. Tumourigenicity of CSCs was determined using a xenograft model in vivo. Effects of EGF receptor inhibitors, Gefitinib and PD153035, on CSC proliferation, apoptosis and signalling were evaluated using fluorescence-activated cell sorting and western blotting. RESULTS Colon cancer cell HCT116 transformed to CSCs in SFM. Compared to other growth factors, EGF was essential to support proliferation of CSCs that expressed higher levels of progenitor genes (Musashi-1, LGR5) and lower levels of differential genes (CK20). CSCs promoted more rapid tumour growth than regular cancer cells in xenografts. EGFR inhibitors suppressed proliferation and induced apoptosis of CSCs by inhibiting autophosphorylation of EGFR and downstream signalling proteins, such as Akt kinase, extracellular signal-regulated kinase 1/2 (ERK 1/2). CONCLUSIONS This study indicates that EGF signalling was essential for formation and maintenance of colon CSCs. Inhibition of the EGF signalling pathway may provide a useful strategy for treatment of colon cancer.
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Affiliation(s)
- Y Feng
- Department of Gastroenterology, Ruijin Hospital, Shanghai Jiaotong University of Medicine, Shanghai, China
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