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Mouse Mammary Tumour Virus (MMTV) in Human Breast Cancer—The Value of Bradford Hill Criteria. Viruses 2022; 14:v14040721. [PMID: 35458452 PMCID: PMC9028876 DOI: 10.3390/v14040721] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 03/24/2022] [Accepted: 03/25/2022] [Indexed: 01/27/2023] Open
Abstract
For many decades, the betaretrovirus, mouse mammary tumour virus (MMTV), has been a causal suspect for human breast cancer. In recent years, substantial new evidence has been developed. Based on this evidence, we hypothesise that MMTV has a causal role. We have used an extended version of the classic A. Bradford Hill causal criteria to assess the evidence. 1. Identification of MMTV in human breast cancers: The MMTV 9.9 kb genome in breast cancer cells has been identified. The MMTV genome in human breast cancer is up to 98% identical to MMTV in mice. 2. Epidemiology: The prevalence of MMTV positive human breast cancer is about 35 to 40% of breast cancers in Western countries and 15 to 20% in China and Japan. 3. Strength of the association between MMTV and human breast cancer: Consistency—MMTV env gene sequences are consistently five-fold higher in human breast cancer as compared to benign and normal breast controls. 4. Temporality (timing) of the association: MMTV has been identified in benign and normal breast tissues up to 10 years before the development of MMTV positive breast cancer in the same patient. 5. Exposure: Exposure of humans to MMTV leads to development of MMTV positive human breast cancer. 6. Experimental evidence: MMTVs can infect human breast cells in culture; MMTV proteins are capable of malignantly transforming normal human breast epithelial cells; MMTV is a likely cause of biliary cirrhosis, which suggests a link between MMTV and the disease in humans. 7. Coherence—analogy: The life cycle and biology of MMTV in humans is almost the same as in experimental and feral mice. 8. MMTV Transmission: MMTV has been identified in human sputum and human milk. Cereals contaminated with mouse fecal material may transmit MMTV. These are potential means of transmission. 9. Biological plausibility: Retroviruses are the established cause of human cancers. Human T cell leukaemia virus type I (HTLV-1) causes adult T cell leukaemia, and human immunodeficiency virus infection (HIV) is associated with lymphoma and Kaposi sarcoma. 10. Oncogenic mechanisms: MMTV oncogenesis in humans probably differs from mice and may involve the enzyme APOBEC3B. Conclusion: In our view, the evidence is compelling that MMTV has a probable causal role in a subset of approximately 40% of human breast cancers.
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Lawson JS, Glenn WK. Evidence for a causal role by mouse mammary tumour-like virus in human breast cancer. NPJ Breast Cancer 2019; 5:40. [PMID: 31728407 PMCID: PMC6838066 DOI: 10.1038/s41523-019-0136-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Accepted: 10/15/2019] [Indexed: 12/17/2022] Open
Abstract
We have reviewed the evidence relevant to mouse mammary tumour viruses (MMTV) and human breast cancer. The prevalence of MMTV- like gene sequences is 15-fold higher in human breast cancer than in normal human breast tissue controls and is present in up to 40% of human breast cancers. MMTV-like gene sequences can be identified in benign breast tissues 1-11 years before the development of positive MMTV-like breast cancer in the same women. The prevalence of MMTV antibodies in sera from women with breast cancer is 5-fold higher than in normal women. MMTV can infect human breast epithelial cells and integrate at random into the human genome located in those cells. MMTV-like gene sequences are present in human milk from normal lactating women and with increased prevalence in milk from women at risk of breast cancer. MMTV-like virus associated human breast cancer has strikingly similar features to MMTV-associated mouse mammary tumours. These features include almost identical nucleotide sequences and structure of the MMTV genome, histology, superantigen expression, MMTV infection of B and T lymphocytes and hormone dependence. MMTV-like gene sequences have also been identified in dogs, cats, monkeys, mice and rats. Saliva has been identified as the most plausible means of transmission from human to human and possibly from dogs to humans. The evidence meets the classic causal criteria. A causal role for MMTV-like viruses in human breast cancer is highly likely.
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Affiliation(s)
- James S. Lawson
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW Australia
| | - Wendy K. Glenn
- School of Biotechnology and Biomolecular Science, University of New South Wales, Sydney, NSW Australia
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3
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Lawson JS, Mazzanti C, Civita P, Menicagli M, Ngan CC, Whitaker NJ, Hochman J, Braitbard O, Yosufi B, Glenn WK. Association of Mouse Mammary Tumor Virus With Human Breast Cancer: Histology, Immunohistochemistry and Polymerase Chain Reaction Analyses. Front Oncol 2018; 8:141. [PMID: 29868468 PMCID: PMC5950654 DOI: 10.3389/fonc.2018.00141] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/18/2018] [Indexed: 12/18/2022] Open
Abstract
Purpose The purpose of this study is to determine whether mouse mammary tumor virus (MMTV)-associated human breast cancer has the same or similar histology to MMTV-associated mouse mammary tumors. Such associations may indicate a role for MMTV in human breast cancer. Methods Immunohistochemical techniques (using antibodies directed against the signal peptide p14 of the envelope precursor protein of MMTV) and polymerase chain reaction (PCR) analyses were used to identify MMTV proteins and MMTV-like envelope gene sequences in a series of breast cancers from Australian women. The histological characteristics of these human breast cancer specimens were compared with MMTV positive mouse mammary tumors. The same methods were used to study benign breast tissues which 1–11 years later developed into breast cancer. Results MMTV p14 proteins were identified in 27 (54%) of 50 human breast cancers. MMTV env gene sequences were identified by PCR in 12 (27%) of 45 human breast cancers. There was a significant correlation between the presence of MMTV (identified by p14 immunohistochemistry) in human breast cancers and histological characteristics similar to MMTV positive mouse mammary tumors (p = 0.001). There was a non-significant correlation between the presence of MMTV env gene sequences (identified by PCR) in human breast cancers and histological characteristics similar to MMTV positive mouse mammary tumors (p = 0.290). MMTV p14 proteins were identified in 7 (54%) of 13 benign breast specimens that later developed into human breast cancers. MMTV by PCR was identified in two benign specimens one of whom later developed MMTV positive breast cancer. Discussion These observations offer evidence that MMTV may be associated with characteristic human breast cancer histology. p14-based immunohistochemistry appears to be a more reliable technique than PCR for the identification of MMTV in human breast cancer. Identification of MMTV-associated p14 proteins in benign breast tissues confirms prior PCR-based studies that MMTV infection occurs before the development of MMTV positive breast cancer. Conclusion Many MMTV positive human breast cancers have similar histology to MMTV positive mouse mammary tumors. MMTV infection identified in benign breast tissues precedes development of MMTV positive human breast cancer. When considered in the context of prior studies, these observations indicate a likely role for MMTV in human breast cancer.
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Affiliation(s)
| | | | | | | | | | | | - Jacob Hochman
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Ori Braitbard
- Department of Cell and Developmental Biology, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Benafsha Yosufi
- Douglass Hanly Moir Pathology, Macquarie Park, NSW, Australia
| | - Wendy K Glenn
- University of New South Wales, Sydney, NSW, Australia
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Lawson JS, Salmons B, Glenn WK. Oncogenic Viruses and Breast Cancer: Mouse Mammary Tumor Virus (MMTV), Bovine Leukemia Virus (BLV), Human Papilloma Virus (HPV), and Epstein-Barr Virus (EBV). Front Oncol 2018; 8:1. [PMID: 29404275 PMCID: PMC5786831 DOI: 10.3389/fonc.2018.00001] [Citation(s) in RCA: 87] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 01/03/2018] [Indexed: 12/18/2022] Open
Abstract
Background Although the risk factors for breast cancer are well established, namely female gender, early menarche and late menopause plus the protective influence of early pregnancy, the underlying causes of breast cancer remain unknown. The development of substantial recent evidence indicates that a handful of viruses may have a role in breast cancer. These viruses are mouse mammary tumor virus (MMTV), bovine leukemia virus (BLV), human papilloma viruses (HPVs), and Epstein–Barr virus (EBV-also known as human herpes virus type 4). Each of these viruses has documented oncogenic potential. The aim of this review is to inform the scientific and general community about this recent evidence. The evidence MMTV and human breast cancer—the evidence is detailed and comprehensive but cannot be regarded as conclusive. BLV and human breast cancer—the evidence is limited. However, in view of the emerging information about BLV in human breast cancer, it is prudent to encourage the elimination of BLV in cattle, particularly in the dairy industry. HPVs and breast cancer—the evidence is substantial but not conclusive. The availability of effective preventive vaccines is a major advantage and their use should be encouraged. EBV and breast cancer—the evidence is also substantial but not conclusive. Currently, there are no practical means of either prevention or treatment. Although there is evidence of genetic predisposition, and cancer in general is a culmination of events, there is no evidence that inherited genetic traits are causal. Conclusion The influence of oncogenic viruses is currently the major plausible hypothesis for a direct cause of human breast cancer.
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Affiliation(s)
- James S Lawson
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
| | | | - Wendy K Glenn
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW, Australia
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Walsh SR, Linnerth-Petrik NM, Laporte AN, Menzies PI, Foster RA, Wootton SK. Full-length genome sequence analysis of enzootic nasal tumor virus reveals an unusually high degree of genetic stability. Virus Res 2010; 151:74-87. [PMID: 20398709 DOI: 10.1016/j.virusres.2010.04.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 04/01/2010] [Accepted: 04/05/2010] [Indexed: 12/18/2022]
Abstract
Enzootic nasal tumor virus (ENTV) is a betaretrovirus of sheep (ENTV-1) and goats (ENTV-2) associated with neoplastic transformation of epithelial cells of the ethmoid turbinate. Confirmation of the role of ENTV in the pathogenesis of enzootic nasal adenocarcinoma (ENA) has yet to be resolved due to the lack of an infectious molecular clone and the inability to culture the virus. Very little is known about the prevalence of this disease, particularly in North America, and only one full-length sequence is available for each of ENTV-1 and ENTV-2. In order to understand the molecular evolution of ENTV-1, the full-length genome sequence of ten ENTV-1 proviruses derived from clinical samples of ENA isolated from conventionally reared sheep in Canada and the United States was determined. The North American ENTV-1 (ENTV-1(NA)) genomes shared greater than 96% sequence identity with the European ENTV-1 sequence (ENTV-1(EU)). Most of the amino acid differences were found in Orf-x, which in the corresponding ENTV-1(EU) genome is truncated by 44 amino acids. Apart from Orf-x, the long terminal repeat (LTR) is where the majority of differences between ENTV-1(NA) and ENTV-1(EU) reside. Overall, there was an unusually high degree of amino acid conservation among the isolates suggesting that ENTV-1 is under stabilizing selection and K(a)/K(s) ratios calculated for each of the viral genes support this hypothesis. The unusually high degree of genetic stability of the ENTV-1 genome enabled us to develop a hemi-nested PCR assay for detection of ENTV-1 in clinical samples. Additionally, multiple nasal tumor cell clones were established and while most had lost the provirus by passage 5; one polyclonal line retained the provirus and attempts are being made to culture these cells. These tumor cells, the first of their kind, may provide a system for studying ENTV-1 in vitro. This work represents an important step in the study of ENTV and sets the foundation for the construction of an infectious molecular clone of ENTV-1.
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Affiliation(s)
- Scott R Walsh
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Zábranský A, Sakalian M, Pichová I. Localization of self-interacting domains within betaretrovirus Gag polyproteins. Virology 2005; 332:659-66. [PMID: 15680431 DOI: 10.1016/j.virol.2004.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 11/13/2004] [Accepted: 12/11/2004] [Indexed: 11/18/2022]
Abstract
The Betaretrovirus genus is characterized by the ability to preassemble immature capsids within the cytoplasm. For Mason-Pfizer monkey virus (M-PMV) this ability depends in part upon the unique Internal Scaffold Domain (ISD) within the p12 region of Gag. In this study, we have further characterized the ability of M-PMV p12 to promote Gag-Gag interaction and have examined the Gag polyprotein of the related mouse mammary tumor virus (MMTV) to potentially identify a region with equivalent function. Using the yeast two-hybrid system, we confirmed that both Gag polyproteins strongly interact, primarily through the CA-NC regions, but also through additional domains N-terminal to CA. For M-PMV, this auxiliary interaction domain was p12. For MMTV, no single strongly self-interacting protein was identified. Instead, MMTV Gag appears to utilize the weak contributions of several protein domains to support the main interaction of its CA-NC. Our findings suggest that, in addition to the canonical NC "I-domain" interaction, MMTV Gag self-association results from the concerted action of multiple regions of the polyprotein while M-PMV Gag relies mainly on its p12 domain.
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Affiliation(s)
- Ales Zábranský
- Department of Protein Biochemistry, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo n.2, Prague 6, 16610, Czech Republic.
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Etkind PR, Stewart AFR, Dorai T, Purcell DJ, Wiernik PH. Clonal isolation of different strains of mouse mammary tumor virus-like DNA sequences from both the breast tumors and non-Hodgkin's lymphomas of individual patients diagnosed with both malignancies. Clin Cancer Res 2005; 10:5656-64. [PMID: 15355890 DOI: 10.1158/1078-0432.ccr-03-0364] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE In a previous study, we had detected the presence of mouse mammary tumor virus (MMTV)-like envelope (ENV) gene sequences in both the breast tumors and non-Hodgkin's lymphoma tissue of two of our breast tumor patients who had been diagnosed simultaneously with both malignancies. The aim of this study was to determine if MMTV-like DNA sequences are present in the breast tumors and non-Hodgkin's lymphomas of additional patients suffering from both malignancies and if so to characterize these sequences in detail. EXPERIMENTAL DESIGN DNA was extracted from formalin-fixed, paraffin-embedded tissue sample blocks of breast tumors and non-Hodgkin's lymphomas from patients suffering from both malignancies. A 250-bp region of the MMTV ENV gene and a 630-bp region of the MMTV long terminal repeat (LTR) open reading frame (ORF) that encodes the MMTV superantigen (sag) gene were amplified by PCR from the isolated DNA. Amplified products were analyzed by Southern blotting, cloned, and sequenced. RESULTS MMTV-like ENV and LTR sequences were detected in both the breast tumors and non-Hodgkin's lymphomas of 6 of 12 patients suffering from both malignancies. A novel mutant of the MMTV ENV gene was identified in these patients. Characterization of the MMTV-like LTR highly variable sag sequences revealed total or nearly total identity to three distinct MMTV proviruses from two different branches of the MMTV phylogenetic tree. CONCLUSIONS The presence of MMTV-like ENV and LTR sequences in both the breast tumors and non-Hodgkin's lymphomas of 6 additional patients suggests a possible involvement of these sequences in these two malignancies. MMTV-like LTR sequence homology to different MMTV proviruses revealed the presence of more than one strain of MMTV-like sequences in each individual suggesting the possibility of multiple infections in these patients.
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MESH Headings
- Aged
- Aged, 80 and over
- Antigens, Viral/genetics
- Base Sequence
- Blotting, Southern
- Breast Neoplasms/complications
- Breast Neoplasms/virology
- DNA, Viral/genetics
- Female
- Genes, env/genetics
- Humans
- Lymphoma, Non-Hodgkin/complications
- Lymphoma, Non-Hodgkin/virology
- Mammary Tumor Virus, Mouse/genetics
- Mammary Tumor Virus, Mouse/isolation & purification
- Middle Aged
- Molecular Sequence Data
- Open Reading Frames
- Phylogeny
- Polymerase Chain Reaction
- Sequence Homology, Nucleic Acid
- Superantigens/genetics
- Terminal Repeat Sequences
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Affiliation(s)
- Polly R Etkind
- Our Lady of Mercy Medical Center-Comprehensive Cancer Center, New York Medical College, Bronx, New York, USA
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8
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Uz-Zaman T, Ignatowicz L, Sarkar NH. Mouse mammary tumor viruses expressed by RIII/Sa mice with a high incidence of mammary tumors interact with the Vβ-2- and Vβ-8-specific T cells during viral infection. Virology 2003; 314:294-304. [PMID: 14517082 DOI: 10.1016/s0042-6822(03)00429-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mouse mammary tumor viruses (MMTVs) that induce mammary adenocarcinomas in mice are transmitted from mother to offspring through milk. MMTV infection results in the deletion of specific T cells as a consequence of interaction between the MMTV-encoded superantigen (Sag) and specific V beta chains of the T cell receptor. The specificity and kinetics of T cell deletion for a number of highly oncogenic MMTVs, such as C3H- and GR-MMTVs, have been studied in great detail. Some work has also been done with the MMTVs expressed in two substrains of RIII mice, BR6 and RIIIS/J, but the nature of the interaction between T cells and the virus(es) that the parental RIII-strain of mice express has not been investigated. Since RIII mice (designated henceforth as RIII/Sa) have a very high incidence (90-98%) of mammary tumors, and they have been extensively used in studies of the biology of mammary tumor development, we have presently determined the pattern of V beta-T cell deletion caused by RIII/Sa-MMTV-Sag(s) during viral infection. T cells were isolated from lymph nodes and thymus of young RIII/Sa mice, as well as from BALB/c (BALB/cfRIII/Sa), C57BL (C57BLfRIII/Sa), and RIIIS/J (RIIIS/JfRIII/Sa) mice after they were infected with RIII/Sa-MMTV(s) by foster nursing. The composition of the T cells was analyzed by FACS using a panel of monoclonal antibodies specific to a variety of V betas. Our results show that milk-borne RIII/Sa-MMTV(s) infection leads to the deletion of CD4(+) V beta-2, and to a lesser extent V beta-8 bearing peripheral and central T cells in RIII/Sa, RIIIS/J, BALB/c, and C57BL mice. Our results are in contrast to the findings that C3H-, GR-, and BR6-MMTVs delete V beta-14- and/or V beta-15-specific T cells.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, Viral
- CD4-Positive T-Lymphocytes/metabolism
- Female
- Incidence
- Lactation
- Mammary Neoplasms, Experimental/virology
- Mammary Tumor Virus, Mouse/metabolism
- Mammary Tumor Virus, Mouse/pathogenicity
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Milk/virology
- Molecular Sequence Data
- Receptors, Antigen, T-Cell, alpha-beta/chemistry
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Retroviridae Infections/virology
- Tumor Virus Infections/virology
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Affiliation(s)
- Taher Uz-Zaman
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA
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Stewart TH, Sage RD, Stewart AF, Cameron DW. Breast cancer incidence highest in the range of one species of house mouse, Mus domesticus. Br J Cancer 2000; 82:446-51. [PMID: 10646903 PMCID: PMC2363264 DOI: 10.1054/bjoc.1999.0941] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Incidence of human breast cancer (HBC) varies geographically, but to date no environmental factor has explained this variation. Previously, we reported a 44% reduction in the incidence of breast cancer in women fully immunosuppressed following organ transplantation (Stewart et al (1995) Lancet 346: 796-798). In mice infected with the mouse mammary tumour virus (MMTV), immunosuppression also reduces the incidence of mammary tumours. DNA with 95% identity to MMTV is detected in 40% of human breast tumours (Wang et al (1995) Cancer Res 55: 5173-5179). These findings led us to ask whether the incidence of HBC could be correlated with the natural ranges of different species of wild mice. We found that the highest incidence of HBC worldwide occurs in lands where Mus domesticus is the resident native or introduced species of house mouse. Given the similar responses of humans and mice to immunosuppression, the near identity between human and mouse MTV DNA sequences, and the close association between HBC incidence and mouse ranges, we propose that humans acquire MMTV from mice. This zoonotic theory for a mouse-viral cause of HBC allows testable predictions and has potential importance in prevention.
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Affiliation(s)
- T H Stewart
- University of Ottawa at Ottawa Hospital, Ontario, Canada.
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10
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Acha-Orbea H, Finke D, Attinger A, Schmid S, Wehrli N, Vacheron S, Xenarios I, Scarpellino L, Toellner KM, MacLennan IC, Luther SA. Interplays between mouse mammary tumor virus and the cellular and humoral immune response. Immunol Rev 1999; 168:287-303. [PMID: 10399081 DOI: 10.1111/j.1600-065x.1999.tb01299.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Mouse mammary tumor virus has developed strategies to exploit the immune response. It requires vigorous immune stimulation to achieve efficient infection. The infected antigen-presenting cells present a viral superantigen on the cell surface which stimulates strong CD4-mediated T-cell help but CD8 T-cell responses are undetectable. Despite the high frequency of superantigen-reactive T cells, the superantigen-induced immune response is comparable to classical antigen responses in terms of T-cell priming, T-cell-B-cell collaboration as well as follicular and extra-follicular B-cell differentiation. Induction of systemic anergy is observed, similar to classical antigen responses where antigen is administered systemically but does not influence the role of the superantigen-reactive T cells in the maintenance of the chronic germinal center reaction. So far we have been unable to detect a cytotoxic T-cell response to mouse mammary tumor virus peptide antigens or to the superantigen. This might yet represent another step in the viral infection strategy.
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Affiliation(s)
- H Acha-Orbea
- Ludwing Institute of Cancer Research, Lausanne Branch, University of Lausanne, Epalinges, Switzerland.
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11
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Reuss FU, Coffin JM. Mouse mammary tumor virus superantigen expression in B cells is regulated by a central enhancer within the pol gene. J Virol 1998; 72:6073-82. [PMID: 9621071 PMCID: PMC110413 DOI: 10.1128/jvi.72.7.6073-6082.1998] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Expression of mouse mammary tumor virus (MMTV)-encoded superantigens in B lymphocytes is required for viral transmission and pathogenesis. The mechanism of superantigen expression from the viral sag gene in B cells is largely unknown, due to problems with detection and quantification of these low-abundance proteins. We have established a sensitive superantigen-luciferase reporter assay to study the expression and regulation of the MMTV sag gene in B-cell lymphomas. The regulatory elements for retroviral gene expression are generally located in the 5' long terminal repeat (LTR) of the provirus. However, we found that neither promoters nor enhancers in the MMTV 5' LTR play a significant role in superantigen expression in these cells. Instead, the essential regulatory regions are located in the pol and env genes of MMTV. We report here that maximal sag expression in B-cell lines depends on an enhancer within the viral pol gene which can be localized to a minimal 183-bp region. Regulation of sag gene expression differs between B-cell lymphomas and pro-B cells, where an enhancer within the viral LTRs is involved. Thus, MMTV sag expression during B-cell development is achieved through the use of two separate enhancer elements.
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Affiliation(s)
- F U Reuss
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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12
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Mouse Mammary Tumor Virus: Immunological Interplays between Virus and Host **This article was accepted for publication on 1 October 1996. Adv Immunol 1997. [DOI: 10.1016/s0065-2776(08)60743-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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13
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Abstract
The current knowledge of the distribution of the mouse mammary tumor virus (MMTV) proviral genomes and the mechanism of mammary tumorigenesis by MMTV in mice, with the main emphasis on Asian feral mice, is reviewed. The relevant earlier discoveries on the mode of MMTV transmission are summarized to provide an outline of the biology of MMTV. Finally, the viral etiology of human breast cancer will be discussed.
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MESH Headings
- Animals
- Animals, Wild/genetics
- Animals, Wild/virology
- Breast Neoplasms/genetics
- DNA, Neoplasm/genetics
- DNA, Viral/analysis
- Female
- Humans
- Mammary Neoplasms, Experimental/genetics
- Mammary Neoplasms, Experimental/virology
- Mammary Tumor Virus, Mouse/genetics
- Mammary Tumor Virus, Mouse/isolation & purification
- Mammary Tumor Virus, Mouse/ultrastructure
- Mice
- Retroviridae Infections/etiology
- Retroviridae Infections/genetics
- Retroviridae Infections/transmission
- Sequence Analysis, DNA
- Tumor Virus Infections/etiology
- Tumor Virus Infections/genetics
- Tumor Virus Infections/transmission
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Affiliation(s)
- S Imai
- Nara Prefectural Institute of Public Health, Japan
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