http://www.mdpi.com/journal/viruses/special_issues/cell-transformation/ Submission All manuscripts should be submitted to viruses@mdpi.com with a copy to the Guest Editor. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Viruses is an international peer-reviewed Open Access monthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. For the first couple of issues, to be published in 2009 and 2010, the Article Processing Charges (APC) in this Open Access journal will be waived for well-prepared manuscripts. English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections. http://www.mdpi.com/1999-4915/3/6/858/ Studies of oncogenic viruses have made seminal contributions to the molecular biology of cancer. Key discoveries include the identification of viral oncogenes and cellular proto-oncogenes, elucidation of signal transduction pathways, and identification of tumor suppressor genes. The origins of cancer virology began almost exactly one hundred years ago with the discovery of avian sarcoma and acute leukemia viruses—RNA-containing viruses of the retrovirus family. The study of animal cancer viruses accelerated beginning in the late 1960s and early 1970s, with the discovery of DNA viruses that could transform cells in culture, and the development of quantitative assays for transformation by DNA and RNA-containing tumor viruses. The discovery of reverse transcriptase in retroviruses in 1970 also greatly accelerated research on these viruses. Indeed RNA and DNA tumor viruses led the way in cancer molecular biology during this era before molecular cloning. It was possible to physically purify virus particles and generate specific hybridization probes for viral DNA and RNA at a time when it was not possible to analyze cellular genes in the same manner. [...] http://www.mdpi.com/1999-4915/3/6/858/ Wed, 15 Jun 2011 00:00:00 CEST Viruses 2011-06-15 3 6 Editorial 858 860 1999-4915 Cell Transformation by RNA Viruses: An Overview 2011-06-15 doi: 10.3390/v3060858 Hung Fan http://www.mdpi.com/1999-4915/3/4/398/ Retroviruses cause cancers in a variety of animals and humans. Research on retroviruses has provided important insights into mechanisms of oncogenesis in humans, including the discovery of viral oncogenes and cellular proto-oncogenes. The subject of this review is the mechanisms by which retroviruses that do not carry oncogenes (non-acute retroviruses) cause cancers. The common theme is that these tumors result from insertional activation of cellular proto-oncogenes by integration of viral DNA. Early research on insertional activation of proto-oncogenes in virus-induced tumors is reviewed. Research on non-acute retroviruses has led to the discovery of new proto-oncogenes through searches for common insertion sites (CISs) in virus-induced tumors. Cooperation between different proto-oncogenes in development of tumors has been elucidated through the study of retrovirus-induced tumors, and retroviral infection of genetically susceptible mice (retroviral tagging) has been used to identify cellular proto-oncogenes active in specific oncogenic pathways. The pace of proto-oncogene discovery has been accelerated by technical advances including PCR cloning of viral integration sites, the availability of the mouse genome sequence, and high throughput DNA sequencing. Insertional activation has proven to be a significant risk in gene therapy trials to correct genetic defects with retroviral vectors. Studies on non-acute retroviral oncogenesis provide insight into the potential risks, and the mechanisms of oncogenesis. http://www.mdpi.com/1999-4915/3/4/398/ Fri, 15 Apr 2011 00:00:00 CEST Viruses 2011-04-15 3 4 Review 398 422 1999-4915 Insertional Oncogenesis by Non-Acute Retroviruses: Implications for Gene Therapy 2011-04-15 doi: 10.3390/v3040398 Hung Fan Chassidy Johnson http://www.mdpi.com/1999-4915/2/12/2618/ Jaagsiekte sheep retrovirus (JSRV) is the causative agent of a lung cancer in sheep known as ovine pulmonary adenocarcinoma (OPA). The disease has been identified around the world in several breeds of sheep and goats, and JSRV infection typically has a serious impact on affected flocks. In addition, studies on OPA are an excellent model for human lung carcinogenesis. A unique feature of JSRV is that its envelope (Env) protein functions as an oncogene. The JSRV Env-induced transformation or oncogenesis has been studied in a variety of cell systems and in animal models. Moreover, JSRV studies have provided insights into retroviral genomic RNA export/expression mechanisms. JSRV encodes a trans-acting factor (Rej) within the env gene necessary for the synthesis of Gag protein from unspliced viral RNA. This review summarizes research pertaining to JSRV‑induced pathogenesis, Env transformation, and other aspects of JSRV biology. http://www.mdpi.com/1999-4915/2/12/2618/ Fri, 03 Dec 2010 00:00:00 CET Viruses 2010-12-03 2 12 Review 2618 2648 1999-4915 Jaagsiekte Sheep Retrovirus Biology and Oncogenesis 2010-12-03 doi: 10.3390/v2122618 Andrew Hofacre Hung Fan http://www.mdpi.com/1999-4915/2/10/2235/ Hematological malignancies in humans typically involve two types of genetic changes: those that promote hematopoietic cell proliferation and survival (often the result of activation of tyrosine kinases) and those that impair hematopoietic cell differentiation (often the result of changes in transcription factors). The multi-stage erythroleukemia induced in mice by Friend spleen focus-forming virus (SFFV) is an excellent animal model for studying the molecular basis for both of these changes. Significant progress has been made in understanding the molecular basis for the multi-stage erythroleukemia induced by Friend SFFV. In the first stage of leukemia, the envelope protein encoded by SFFV interacts with and activates the erythropoietin (Epo) receptor and the receptor tyrosine kinase sf-Stk in erythroid cells, causing their Epo-independent proliferation, differentiation and survival. In the second stage, SFFV integration into the Sfpi1 locus activates the myeloid transcription factor PU.1, blocking erythroid cell differentiation, and in conjunction with the loss of p53 tumor suppressor activity, results in the outgrowth of malignant cells. In this review, we discuss the current level of understanding of how SFFV alters the growth and differentiation of erythroid cells and results in the development of erythroleukemia. Our knowledge of how SFFV causes erythroleukemia in mice may give us clues as to how the highly related human retrovirus XMRV causes malignancies in humans. http://www.mdpi.com/1999-4915/2/10/2235/ Mon, 11 Oct 2010 00:00:00 CEST Viruses 2010-10-11 2 10 Review 2235 2257 1999-4915 Friend Spleen Focus-Forming Virus Activates the Tyrosine Kinase sf-Stk and the Transcription Factor PU.1 to Cause a Multi-Stage Erythroleukemia in Mice 2010-10-11 doi: 10.3390/v2102235 Joan Cmarik Sandra Ruscetti http://www.mdpi.com/1999-4915/2/9/2108/ Chronic hepatitis C virus (HCV) infection is a major risk factor for liver disease progression, and may lead to cirrhosis and hepatocellular carcinoma (HCC). The HCV genome contains a single-stranded positive sense RNA with a cytoplasmic lifecycle. HCV proteins interact with many host-cell factors and are involved in a wide range of activities, including cell cycle regulation, transcriptional regulation, cell proliferation, apoptosis, lipid metabolism, and cell growth promotion. Increasing experimental evidences suggest that HCV contributes to HCC by modulating pathways that may promote malignant transformation of hepatocytes. At least four of the 10 HCV gene products, namely core, NS3, NS5A and NS5B play roles in several potentially oncogenic pathways. Induction of both endoplasmic reticulum (ER) stress and oxidative stress by HCV proteins may also contribute to hepatocyte growth promotion. The current review identifies important functions of the viral proteins connecting HCV infections and potential for development of HCC. However, most of the putative transforming potentials of the HCV proteins have been defined in artificial cellular systems, and need to be established relevant to infection and disease models. The new insight into the mechanisms for HCV mediated disease progression may offer novel therapeutic targets for one of the most devastating human malignancies in the world today. http://www.mdpi.com/1999-4915/2/9/2108/ Mon, 27 Sep 2010 00:00:00 CEST Viruses 2010-09-27 2 9 Review 2108 2133 1999-4915 Oncogenic Potential of Hepatitis C Virus Proteins 2010-09-27 doi: 10.3390/v2092108 Arup Banerjee Ratna B. Ray Ranjit Ray http://www.mdpi.com/1999-4915/2/9/2037/ Human T lymphotropic viruses (HTLVs) are complex deltaretroviruses that do not contain a proto-oncogene in their genome, yet are capable of transforming primary T lymphocytes both in vitro and in vivo. There are four known strains of HTLV including HTLV type 1 (HTLV-1), HTLV-2, HTLV-3 and HTLV-4. HTLV-1 is primarily associated with adult T cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-2 is rarely pathogenic and is sporadically associated with neurological disorders. There have been no diseases associated with HTLV-3 or HTLV-4 to date. Due to the difference in the disease manifestation between HTLV-1 and HTLV-2, a clear understanding of their individual pathobiologies and the role of various viral proteins in transformation should provide insights into better prognosis and prevention strategies. In this review, we aim to summarize the data accumulated so far in the transformation and pathogenesis of HTLV-1, focusing on the viral Tax and HBZ and citing appropriate comparisons to HTLV-2. http://www.mdpi.com/1999-4915/2/9/2037/ Fri, 24 Sep 2010 00:00:00 CEST Viruses 2010-09-24 2 9 Review 2037 2077 1999-4915 Human T Lymphotropic Virus Type 1 (HTLV-1): Molecular Biology and Oncogenesis 2010-09-24 doi: 10.3390/v2092037 Priya Kannian Patrick L. Green http://www.mdpi.com/1999-4915/2/9/2000/ Mouse mammary tumor virus (MMTV), which was discovered as a milk‑transmitted, infectious cancer-inducing agent in the 1930s, has been used since that time as an animal model for the study of human breast cancer. Like other complex retroviruses, MMTV encodes a number of accessory proteins that both facilitate infection and affect host immune response. In vivo, the virus predominantly infects lymphocytes and mammary epithelial cells. High level infection of mammary epithelial cells ensures efficient passage of virus to the next generation. It also results in mammary tumor induction, since the MMTV provirus integrates into the mammary epithelial cell genome during viral replication and activates cellular oncogene expression. Thus, mammary tumor induction is a by-product of the infection cycle. A number of important oncogenes have been discovered by carrying out MMTV integration site analysis, some of which may play a role in human breast cancer. http://www.mdpi.com/1999-4915/2/9/2000/ Thu, 23 Sep 2010 00:00:00 CEST Viruses 2010-09-23 2 9 Review 2000 2012 1999-4915 Mouse Mammary Tumor Virus Molecular Biology and Oncogenesis 2010-09-23 doi: 10.3390/v2092000 Susan R. Ross http://www.mdpi.com/1999-4915/2/9/1984/ Retroviruses have been detected in most vertebrate species and are etiologic agents of a variety of neoplastic diseases. The study of retroviruses has been instrumental in uncovering the molecular mechanisms responsible for oncogenesis. Retroviruses have been isolated from three neoplastic diseases in fish, two of which affect the dermis and regress naturally coincident with spawning. This feature provides a unique model to study mechanisms of tumor development and regression. Three complex retroviruses, isolated from walleye (Sander vitreus) with dermal sarcoma and epidermal hyperplasia, are the members of the newest retroviral genus, Epsilonretrovirus. Three accessory proteins, encoded by walleye dermal sarcoma virus (WDSV), function in the regulation of host and viral gene expression and cell cycle, alter cell-signaling pathways to promote cell proliferation and block apoptosis, and, finally, induce apoptosis through dissipation of the mitochondrial membrane potential. http://www.mdpi.com/1999-4915/2/9/1984/ Wed, 22 Sep 2010 00:00:00 CEST Viruses 2010-09-22 2 9 Review 1984 1999 1999-4915 Walleye Dermal Sarcoma Virus: Molecular Biology and Oncogenesis 2010-09-22 doi: 10.3390/v2091984 Joel Rovnak Sandra L. Quackenbush