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Bernal A, Zafon E, Domínguez D, Bertran E, Tusell L. Generation of Immortalised But Unstable Cells after hTERT Introduction in Telomere-Compromised and p53-Deficient vHMECs. Int J Mol Sci 2018; 19:ijms19072078. [PMID: 30018248 PMCID: PMC6073565 DOI: 10.3390/ijms19072078] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 07/11/2018] [Accepted: 07/13/2018] [Indexed: 01/08/2023] Open
Abstract
Telomeres, the natural ends of chromosomes, hide the linear telomeric DNA from constitutive exposure to the DNA damage response with a lariat structure or t-loop. Progressive telomere shortening associated with DNA replication in the absence of a compensatory mechanism culminates in t-loop collapse and unmasked telomeres. Dysfunctional telomeres can suppress cancer development by engaging replicative senescence or apoptosis, but they can also promote tumour initiation when cell cycle checkpoints are disabled. In this setting, telomere dysfunction promotes increasing chromosome instability (CIN) through breakage-fusion-bridge cycles. Excessive instability may hamper cell proliferation but might allow for the appearance of some rare advantageous mutations that could be selected and ultimately favour neoplastic progression. With the aim of generating pre-malignant immortalised cells, we ectopically expressed telomerase in telomere-compromised variant human mammary epithelial cells (vHMECs), proficient and deficient for p53, and analysed structural and numerical chromosomal aberrations as well as abnormal nuclear morphologies. Importantly, this study provides evidence that while immortalisation of vHMECs at early stages results in an almost stable karyotype, a transient telomere-dependent CIN period—aggravated by p53 deficiency—and followed by hTERT overexpression serves as a mechanism for the generation of immortal unstable cells which, due to their evolving karyotype, could attain additional promoting properties permissive to malignancy.
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Affiliation(s)
- Aina Bernal
- Unitat de Biologia Cel·lular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
| | - Elisenda Zafon
- Unitat de Biologia Cel·lular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
| | - Daniel Domínguez
- Unitat de Biologia Cel·lular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
| | - Enric Bertran
- Unitat de Biologia Cel·lular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
| | - Laura Tusell
- Unitat de Biologia Cel·lular, Facultat de Biociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.
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Bele A, Mirza S, Zhang Y, Ahmad Mir R, Lin S, Kim JH, Gurumurthy CB, West W, Qiu F, Band H, Band V. The cell cycle regulator ecdysoneless cooperates with H-Ras to promote oncogenic transformation of human mammary epithelial cells. Cell Cycle 2015; 14:990-1000. [PMID: 25616580 DOI: 10.1080/15384101.2015.1006982] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The mammalian ortholog of Drosophila ecdysoneless (Ecd) gene product regulates Rb-E2F interaction and is required for cell cycle progression. Ecd is overexpressed in breast cancer and its overexpression predicts shorter survival in patients with ErbB2-positive tumors. Here, we demonstrate Ecd knock down (KD) in human mammary epithelial cells (hMECs) induces growth arrest, similar to the impact of Ecd Knock out (KO) in mouse embryonic fibroblasts. Furthermore, whole-genome mRNA expression analysis of control vs. Ecd KD in hMECs demonstrated that several of the top 40 genes that were down-regulated were E2F target genes. To address the role of Ecd in mammary oncogenesis, we overexpressed Ecd and/or mutant H-Ras in hTERT-immortalized hMECs. Cell cycle analyses revealed hMECs overexpressing Ecd+Ras showed incomplete arrest in G1 phase upon growth factor deprivation, and more rapid cell cycle progression in growth factor-containing medium. Analyses of cell migration, invasion, acinar structures in 3-D Matrigel and anchorage-independent growth demonstrated that Ecd+Ras-overexpressing cells exhibit substantially more dramatic transformed phenotype as compared to cells expressing vector, Ras or Ecd. Under conditions of nutrient deprivation, Ecd+Ras-overexpressing hMECs exhibited better survival, with substantial upregulation of the autophagy marker LC3 both at the mRNA and protein levels. Significantly, while hMECs expressing Ecd or mutant Ras alone did not form tumors in NOD/SCID mice, Ecd+Ras-overexpressing hMECs formed tumors, clearly demonstrating oncogenic cooperation between Ecd and mutant Ras. Collectively, we demonstrate an important co-oncogenic role of Ecd in the progression of mammary oncogenesis through promoting cell survival.
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Affiliation(s)
- Aditya Bele
- a Departments of Genetics ; Cell Biology and Anatomy ; Nebraska Medical Center , Omaha , NE USA
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Walia V, Yu Y, Cao D, Sun M, McLean JR, Hollier BG, Cheng J, Mani SA, Rao K, Premkumar L, Elble RC. Loss of breast epithelial marker hCLCA2 promotes epithelial-to-mesenchymal transition and indicates higher risk of metastasis. Oncogene 2011; 31:2237-46. [PMID: 21909135 PMCID: PMC4154589 DOI: 10.1038/onc.2011.392] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Transition between epithelial and mesenchymal states is a feature of both normal development and tumor progression. We report that expression of chloride channel accessory protein hCLCA2 is a characteristic of epithelial differentiation in the immortalized MCF10A and HMLE models, while induction of EMT by cell dilution, TGFbeta, or mesenchymal transcription factors sharply reduces hCLCA2 levels. Attenuation of hCLCA2 expression by lentiviral shRNA caused cell overgrowth and focus formation, enhanced migration and invasion, and increased mammosphere formation in methylcellulose. These changes were accompanied by downregulation of E-cadherin and upregulation of mesenchymal markers such as vimentin and fibronectin. Moreover, hCLCA2 expression is greatly downregulated in breast cancer cells with a mesenchymal or claudin-low profile. These observations suggest that loss of hCLCA2 may promote metastasis. We find that higher-than-median expression of hCLCA2 is associated with a one-third lower rate of metastasis over an 18 year period among breast cancer patients compared to lower-than-median (n=344, unfiltered for subtype). Thus, hCLCA2 is required for epithelial differentiation, and its loss during tumor progression contributes to metastasis. Overexpression of hCLCA2 has been reported to inhibit cell proliferation and is accompanied by increases in chloride current at the plasma membrane and reduced intracellular pH (pHi). We found that knockdown cells have sharply reduced chloride current and higher pHi, both characteristics of tumor cells. These results suggest a mechanism for the effects on differentiation. Loss of hCLCA2 may allow escape from pHi homeostatic mechanisms, permitting the higher intracellular and lower extracellular pH that are characteristic of aggressive tumor cells.
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Affiliation(s)
- V Walia
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL 19629, USA
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Konishi H, Karakas B, Abukhdeir AM, Lauring J, Gustin JP, Garay JP, Konishi Y, Gallmeier E, Bachman KE, Park BH. Knock-in of mutant K-ras in nontumorigenic human epithelial cells as a new model for studying K-ras mediated transformation. Cancer Res 2007; 67:8460-7. [PMID: 17875684 DOI: 10.1158/0008-5472.can-07-0108] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The oncogenic function of mutant ras in mammalian cells has been extensively investigated using multiple human and animal models. These systems include overexpression of exogenous mutant ras transgenes, conditionally expressed knock-in mouse models, and somatic cell knockout of mutant and wild-type ras genes in human cancer cell lines. However, phenotypic discrepancies between knock-in mice and transgenic mutant ras overexpression prompted us to evaluate the consequences of targeted knock-in of an oncogenic K-ras mutation in the nontumorigenic human breast epithelial cell line MCF-10A and hTERT-immortalized human mammary epithelial cells. Our results show several significant differences between mutant K-ras knock-in cells versus their transgene counterparts, including limited phosphorylation of the downstream molecules extracellular signal-regulated kinase and AKT, minor proliferative capacity in the absence of an exogenous growth factor, and the inability to form colonies in semisolid medium. Analysis of 16 cancer cell lines carrying mutant K-ras genes indicated that 50% of cancer cells harbor nonoverexpressed heterozygous K-ras mutations similar to the expression seen in our knock-in cell lines. Thus, this system serves as a new model for elucidating the oncogenic contribution of mutant K-ras as expressed in a large fraction of human cancer cells.
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Affiliation(s)
- Hiroyuki Konishi
- The Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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Rao K, Alper Ö, Opheim KE, Bonnet G, Wolfe K, Bryant E, Larivee SO, Porter P, McDougall JK. Cytogenetic characterization and H-ras associated transformation of immortalized human mammary epithelial cells. Cancer Cell Int 2006; 6:15. [PMID: 16729884 PMCID: PMC1524989 DOI: 10.1186/1475-2867-6-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Accepted: 05/26/2006] [Indexed: 01/09/2023] Open
Abstract
INTRODUCTION Immortalization is a key step in malignant transformation, but immortalization alone is insufficient for transformation. Human mammary epithelial cell (HMEC) transformation is a complex process that requires additional genetic changes beyond immortalization and can be accomplished in vitro by accumulation of genetic changes and expression of H-ras. METHODS HMEC were immortalized by serial passaging and transduction with the catalytic subunit of the human telomerase gene (hTERT). The immortalized cells were passaged in vitro and studied by a combination of G-banding and Spectral Karyotyping (SKY). H-ras transduced, hTERT immortalized cells were cloned in soft agar and injected into nude mice. Extensive analysis was performed on the tumors that developed in nude mice, including immunohistochemistry and western blotting. RESULTS Immortal HMEC alone were not tumorigenic in gamma-irradiated nude mice and could not grow in soft agar. Late passage hTERT immortalized HMEC from a donor transduced with a retroviral vector containing the mutant, autoactive, human H-ras61L gene acquired anchorage independent growth properties and the capacity for tumorigenic growth in vivo. The tumors that developed in the nude mice were poorly differentiated epithelial carcinomas that continued to overexpress ras. These cells were resistant to doxorubicin mediated G1/S phase arrest but were sensitive to treatment with a farnesyltransferase inhibitor. CONCLUSION Some of the cytogenetic changes are similar to what is observed in premalignant and malignant breast lesions. Despite these changes, late passage immortal HMEC are not tumorigenic and could only be transformed with overexpression of a mutant H-ras oncogene.
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Affiliation(s)
- Krishna Rao
- Southern Illinois University School of Medicine Cancer Institute, P.O. Box 19678, Springfield, IL 62794-9678, USA
| | - Özge Alper
- National Institutes of Health, National Institute of Neurological Disorders, Surgical Neurology, Bldg 10, 5D37, Bethesda, MD 20892-1414, USA
| | - Kent E Opheim
- Children's Hospital and Regional Medical Center, Dept. of Laboratories, A-6901 4800 Sand Point Way, NE, Seattle, WA 98105, USA
| | - George Bonnet
- Cytogenetics Studio, Inc., 41 Myrtle Ave., Cambridge, MA 02138, USA
| | | | - Eileen Bryant
- Fred Hutchinson Cancer Research Center, Clinical Research Division, P.O. Box 19024, 1100 Fairview Avenue North, D2-190, Seattle, WA 98109-1024, USA
- Seattle Cancer Care Alliance, 825 Eastlake Avenue East, Mailstop G7500, Seattle, WA 98109, USA
| | - Siobhan O'Hara Larivee
- Seattle Cancer Care Alliance, 825 Eastlake Avenue East, Mailstop G7500, Seattle, WA 98109, USA
| | - Peggy Porter
- Fred Hutchinson Cancer Research Center, Cancer Biology Program, P.O. Box 19024, 1100 Fairview Avenue North, C1-015, Seattle, WA, 98109-1024, USA
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - James K McDougall
- Fred Hutchinson Cancer Research Center, Cancer Biology Program, P.O. Box 19024, 1100 Fairview Avenue North, C1-015, Seattle, WA, 98109-1024, USA
- Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA
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Abstract
A novel breast cancer cell line (RAO-3) was established by transduction of the Q61L mutant RAS into human mammary epithelial cells that were immortalized with catalytic subunit of telomerase (hTERT). The cells displayed anchorage-independent growth and proliferation, and formed human mammary spindle cell carcinoma when injected into nude mice. Chromosome locus 1q22-23 was partially duplicated and inverted on one of the 3 chromosomes present in the cell line. We report here that mutations of chromosome 1q22-23 locus have resulted in the loss of RAB25 expression in the breast cancer cell line. Transduction of RAB25 into the breast cancer cell line arrests anchorage-independent growth. We have also demonstrated loss of RAB25 in human breast tumor tissue. These data suggest that loss of RAB25 might contribute to tumorigenesis of breast cancer, and RAB25 is likely to be an important factor in the development of breast cancer. RAB25 could be used as biological marker of breast cancer and provides a target for gene replacement therapy.
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MESH Headings
- Animals
- Biomarkers, Tumor/analysis
- Blotting, Western
- Breast Neoplasms/chemistry
- Carcinoma/chemistry
- Cell Line, Tumor
- Chromosomes, Human, Pair 1
- Chromosomes, Human, Pair 3
- DNA-Binding Proteins
- Female
- Gene Expression Regulation, Neoplastic
- Genes, ras
- Glutamine
- Humans
- In Situ Hybridization, Fluorescence
- Leucine
- Mice
- Mice, Nude
- Mutation
- Plasmids
- Reverse Transcriptase Polymerase Chain Reaction
- Telomerase
- Transduction, Genetic
- rab GTP-Binding Proteins/analysis
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Affiliation(s)
- Ji-Ming Cheng
- Division of Hematology and Oncology, Department of Internal Medicine, Southern Illinois University School of Medicine, Springfield, 62794, USA
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