As the mechanisms leading to the persistence of hepatitis B virus (HBV) infection are poorly understood and as the histocompatibility leucocyte antigen (HLA)‐G is well described as a tolerogenic ...molecule, we evaluated HLA‐G expression in 74 specimens of HBV liver biopsies and in 10 specimens obtained from previously healthy cadaver liver donors. HBV specimens were reviewed and classified by the METAVIR score, and HLA‐G expression was assessed by immunohistochemistry. No HLA‐G expression was observed in control hepatocytes. In contrast, 57 (77%) of 74 HBV specimens showed soluble and membrane‐bound HLA‐G expression in hepatocytes, biliary epithelial cells or both. No associations between the intensity of HLA‐G expression and patient age or gender, HBeAg status, severity of liver fibrosis, and grade of histological findings were observed. Although significance was not reached (P = 0.180), patients exhibiting HLA‐G expression presented a higher median HBV DNA viral load (105 copies/mL) than those who did not express HLA‐G (103.7 copies/mL). These results indicate that HLA‐G is expressed in most cases of chronic HBV infection in all stages and may play a role in the persistency of HBV infection.
•In more than 85% of cancer cells, unlike normal cells, telomerase activity is continuously expressed, and telomere lengths remain constant due to telomerase reactivation.•Are viruses capable of ...developing cancer by interacting with telomerase, and can target the telomerase activated cancer cells for cancer treatment?•Several DNA and RNA oncoviruses can integrate their genome sequence within the host cell telomeres or interact with telomerase through viral oncoproteins.•These can increase telomerase activity, and cells continue to proliferate which ultimately lead to cancer development.•There are several strategies for targeting cancer cell telomerase to overcome tumor-mediated toleration mechanisms and induce apoptosis, such as virotherapy, telomerase-targeted peptide vaccines, hTERT-targeting dendritic cells (DCs), hTERT-targeting gene therapy, and CRISPR/Cas9 system.
Human telomerase reverse transcriptase (hTERT) is an enzyme that is critically involved in elongating and maintaining telomeres length to control cell life span and replicative potential. Telomerase activity is continuously expressed in human germ-line cells and most cancer cells, whereas it is suppressed in most somatic cells. In normal cells, by reducing telomerase activity and progressively shortening the telomeres, the cells progress to the senescence or apoptosis process. However, in cancer cells, telomere lengths remain constant due to telomerase's reactivation, and cells continue to proliferate and inhibit apoptosis, and ultimately lead to cancer development and human death due to metastasis. Studies demonstrated that several DNA and RNA oncoviruses could interact with telomerase by integrating their genome sequence within the host cell telomeres specifically. Through the activation of the hTERT promoter and lengthening the telomere, these cells contributes to cancer development. Since oncoviruses can activate telomerase and increase hTERT expression, there are several therapeutic strategies based on targeting the telomerase of cancer cells like telomerase-targeted peptide vaccines, hTERT-targeting dendritic cells (DCs), hTERT-targeting gene therapy, and hTERT-targeting CRISPR/Cas9 system that can overcome tumor-mediated toleration mechanisms and specifically apoptosis in cancer cells. This study reviews available data on the molecular structure of telomerase and the role of oncoviruses and telomerase interaction in cancer development and telomerase-dependent therapeutic approaches to conquest the cancer cells.
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Is cancer a contagious disease? In the late nineteenth century this idea, and attending efforts to identify a cancer "germ, " inspired fear and ignited controversy. Yet speculation that cancer might ...be contagious also contained a kernel of hope that the strategies used against infectious diseases, especially vaccination, might be able to subdue this dread disease. Today, nearly one in six cancers are thought to have an infectious cause, but the path to that understanding was twisting and turbulent. ? A Contagious Cause is the first book to trace the century-long hunt for a human cancer virus in America, an effort whose scale exceeded that of the Human Genome Project. The government's campaign merged the worlds of molecular biology, public health, and military planning in the name of translating laboratory discoveries into useful medical therapies. However, its expansion into biomedical research sparked fierce conflict. Many biologists dismissed the suggestion that research should be planned and the idea of curing cancer by a vaccine or any other means as unrealistic, if not dangerous. Although the American hunt was ultimately fruitless, this effort nonetheless profoundly shaped our understanding of life at its most fundamental levels. A Contagious Cause links laboratory and legislature as has rarely been done before, creating a new chapter in the histories of science and American politics.
The study of tumor viruses paves the way for understanding the mechanisms of virus pathogenesis, including those involved in establishing infection and dissemination in the host tumor affecting ...immune-compromised patients. The processes ranging from viral infection to progressing malignancy are slow and usually insufficient for establishment of transformed cells that develop cancer in only a minority of infected subjects. Therefore, viral infection is usually not the only cause of cancer, and further environmental and host factors, may be implicated. HTLV-I, in particular, is considered as an oncovirus cause of lymphoproliferative disease such as adult T cell leukemia/lymphoma (ATL) and disturbs the immune responses which results in HTLV-I associated meylopathy/tropical spastic parapresis (HAM/TSP). HTLV-I infection causes ATL in a small proportion of infected subjects (2-5%) following a prolonged incubation period (15-30 years) despite a strong adaptive immune response against the virus. Overall, these conditions offer a prospect to study the molecular basis of tumorgenicity in mammalian cells. In this review, the oncogencity of HTLV-I is being considered as an oncovirus in context of ATL.
Eight percent of our DNA contains retroviruses that are millions of years old. Anna Marie Skalka explains how our evolving knowledge of these particles has advanced genetic engineering, gene delivery ...systems, and precision medicine. Retroviruses cause disease but also hold clues to prevention and treatment possibilities that are anything but retro.
There are three major types of human retroviruses, namely HIV, HTLV, and endogenous human retroviruses. This book presents the latest findings on the replication of these human retroviruses. This ...book is unique in that there has been no comparable book that integrates the findings from the three known classes of human retroviruses. Other books have focused on one of the three classes of human retroviruses individually.An accomplished international team of contributing authors have combined their expertise to provide cutting-edge findings in this important field. The book will be a valuable reference for students, researchers and medical professionals.
Human oncogenic viruses Ou, Jing-Hsiung James; Yen, T.S. Benedict
2010., 2009, 2009-12-21
eBook
Viruses are the causes of approximately 25% of human cancers. Due to their importance in carcinogenesis, there is a desperate need for a book that discusses these viruses. This book is therefore ...timely, providing a comprehensive review of the molecular biology of oncogenic viruses and the cancers they cause. Viruses that are discussed in the individual chapters include hepatitis B virus, hepatitis C virus, human papilloma viruses, Epstein–Barr virus, Kaposi's sarcoma virus and human T-cell leukemia virus type 1.
The introduction of new HPV vaccines has garnered much research and media attention to the role of infectious agents in cancer. This current and comprehensive text provides an excellent review of the ...basic science and clinical implications of individual infectious agents in cancer. Covering HPV and five additional infectious agents, this text goes beyond a mere update of the literature to offer insights on the emerging possibilities for cancer prevention.
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