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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The first consistent observations that viruses could be associated with some types of cancer where made almost a century ago. Since then researchers have spent a great deal of effort to address the infectious origins of human cancer. As a result of these studies, a strong link between some viral agents and several human cancers has been established. Some viruses as the Epstein-Barr virus (EBV), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-cell lymphotropic virus type I (HTLV-I), immunodeficiency virus type I (HIV-I) and several human papillomavirus types (including types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 and 66) have been classified as group 1 carcinogens by the International Agency for Research in Cancer (IARC). Infection by these viruses constitutes a heavy burden for human populations as it accounts for almost 15% of all human malignancies. Furthermore, many other viral agents have been classified as possibly carcinogenic to humans and others have been occasionally found in human tumors suggesting that this figure may be an underestimation of virus involvement in the etiology of human cancer. Therefore, viral infection appears as one of the main preventable cancer risk factors. We summarize the current state of knowledge concerning virus-induced/associated cancers and discuss its significance in the context of human carcinogenesis. Prevention and control of infection by these agents could dramatically reduce the incidence of some prevalent cancers and, consequently, have a great impact on public health.
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PMID:Viral origins of human cancer. 1797 5

Infection by high risk papillomavirus causes various forms of anogenital cancer including squamous cell carcinoma of the cervix. A primary step in the carcinogenesis includes formation of a complex of viral E6 protein and a human E3 ubiquitin ligase. This complex is competent to cause degradation and inactivation of several target proteins including human tumor suppressors which contributes to hyperproliferation of infected cells. Great insight on the mechanism by which E6 binds target proteins has recently been provided by determination of structures of interacting peptides and a E6 domain. These data have also provided a basis for the discovery of small molecules that can inhibit E6. However, there is still a need to further solve the structures of additional interacting complexes to identify the structural relationship that exists between proteins that simultaneously bind E6, such as E6AP and p53 or E6AP and PDZ domain-containing proteins, and to provide a clear picture of the interface between E6 and its ubiquitin ligase.
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PMID:Structure and function of the papillomavirus E6 protein and its interacting proteins. 1798 32

Infection with HPV (human papillomavirus) 16 is the cause of 50% or more of cervical cancers in women. HPV16 infection, however, is very common in young sexually active women, but the majority mount an effective immune response and clear infection. Approx. 10% of individuals develop a persistent infection, and it is this cohort who are at risk of cancer progression, with the development of high-grade precursor lesions and eventually invasive carcinoma. Effective evasion of innate immune recognition seems to be the hallmark of HPV infections, since the infectious cycle is one in which viral replication and release is not associated with inflammation. Furthermore, HPV infections disrupt cytokine expression and signalling with the E6 and E7 oncoproteins particularly targeting the type I IFN (interferon) pathway. High doses of IFN can overcome the HPV-mediated abrogation of signalling, and this may be the basis for the therapeutic effects on HPV infections of immune-response modulators such as the imidazoquinolones that induce high levels of type I IFNs by activation of TLR (Toll-like receptor) 7. Using the unique W12 model of cervical carcinogenesis, some of these IFN-related interactions and their relevance in the selection of cells with integrated viral DNA in cancer progression have been investigated. Our data show that episome loss associated with induction of antiviral response genes is a key event in the spontaneous selection of cervical keratinocytes containing integrated HPV16. Exogenous IFN-beta treatment of W12 keratinocytes in which the majority of the population contain episomes results only in the rapid emergence of IFN-resistant cells, loss of episome-containing cells and a selection of cells containing integrated HPV16 in which the expression of the transcriptional repressor E2 is down-regulated, but in which E6 and E7 are up-regulated.
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PMID:HPV: from infection to cancer. 1803 Dec 45

Infection with high-risk human papillomaviruses (HPV) and in particular the expression of the viral proteins E6 and E7 have been associated with the etiology of a subset of head and neck squamous cell cancer (HNSCC). However, the individual consequences of E6 and E7 expression in an in vivo model have not been examined in these tissues. We have used transgenes that direct expression of the HPV16 E6 and E7 proteins to the head and neck tissues of mice to dissect the contribution of these proteins to head and neck carcinogenesis. We report here that E7 is the major transforming oncogene in HPV-associated HNSCC, whereas E6 is more likely to play a secondary role in contributing to later stages of carcinogenesis. Furthermore, a conditional deletion of Rb, a prominent target for E7, in the same tissues did not recapitulate all E7-mediated phenotypes. Although our results do not preclude an important role for the E7-pRb interaction, they highlight the importance of pRb-independent functions of E7 in head and neck carcinogenesis.
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PMID:Role of Rb-dependent and Rb-independent functions of papillomavirus E7 oncogene in head and neck cancer. 1808 87

Chronic gastritis induced by Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, yet the effects of bacterial eradication on carcinogenesis remain unclear. Animal models provide important insights into factors that are involved in gastric carcinogenesis, and we previously utilized such a model to demonstrate that an in vivo-adapted H. pylori strain, 7.13, rapidly and reproducibly induces inflammation-mediated gastric carcinoma. In the current study, we used this bacterial strain as a prototype to define the role of targeted antimicrobial therapy in gastric carcinogenesis. Mongolian gerbils were infected with H. pylori for 4 or 8 weeks, treated with antimicrobial agents or vehicle, and then euthanized at 8 weeks after the completion of therapy. All infected gerbils developed gastritis; however, inflammation was significantly attenuated in animals receiving antimicrobial therapy. Gastric dysplasia or cancer developed in >60% of the gerbils that remained persistently colonized with H. pylori, but in none of the animals treated with antibiotics following 4 weeks of infection. Infection with H. pylori for 8 weeks prior to therapy resulted in an attenuation, but not complete prevention, of pre-malignant and malignant lesions. Similarly, antibiotic therapy initiated at 4, but not 8, weeks after H. pylori challenge significantly reduced expression of the Th1 pro-inflammatory cytokine interferon-gamma within colonized gastric mucosa. These results indicate that treatment of H. pylori in this model decreases the incidence and severity of lesions with carcinogenic potential. The effectiveness of eradication is dependent upon the timing of intervention, providing insights into mechanisms that may regulate the development of malignancies arising within the context of inflammatory states.
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PMID:Effect of Helicobacter pylori eradication on gastric carcinogenesis. 1818 Jul

Gastrointestinal cancers account for 20% of all cancer incidences worldwide. Colorectal cancer is the second most common cause of all cancer-related mortality and is increasing in Western societies. Infection and inflammation contribute to 15-20% of all malignancies, and are predisposing risk factors for gastrointestinal cancers. Helicobacter pylori infection is commonly associated with gastric cancers, and chronic inflammation increases the risk of colorectal cancer by 1% per year. Micronutrient status and common genetic variations in human populations modify risk for gastrointestinal cancer. Chronic inflammation promotes carcinogenesis by inducing gene mutations, inhibiting apoptosis, and stimulating angiogenesis and cell proliferation. Inflammation also induces epigenetic alterations that are associated with cancer development. Two key genes in the inflammatory process, cyclooxygenase-2 (COX-2) and nuclear factor-kappa B (NF-kappaB), provide a mechanistic link between inflammation and cancer and are targets for chemoprevention. Dietary components, and human genetic variation that affects nutrient utilization, can directly modify inflammatory processes and/or suppress genomic alterations that are the molecular antecedents of cancers. The present report focuses on the convergence of genetic, nutritional, and inflammatory factors in the initiation and progression of gastrointestinal cancers, and the emerging dietary strategies for cancer prevention.
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PMID:Convergence of genetic, nutritional and inflammatory factors in gastrointestinal cancers. 1824 May 41

Infection load and the integration of human papillomaviruses (HPV) have been implicated as determinants for oncogenesis, but whether variation among different HPV types exists remains unclear. We investigated 91 women infected with HPV type 52 (HPV-52), a type that is rare worldwide but common in East Asia. The median viral load increased with the severity of the lesion (248 copies/cell equivalent for normal/cervical intraepithelial neoplasia [CIN] grade 1, 402 copies/cell equivalent for CIN 2, 523 copies/cell equivalent for CIN 3, and 1,435 copies/cell equivalent for invasive cancer). The proportion of specimens with integration increased significantly with the severity of the lesion (P < 0.001). The viral load was associated with the physical status of the viral genome, with higher levels for the pure episomal form (P = 0.001). Infection status should be considered when interpreting viral load data for HPV-52, as single infections with this HPV type were found to have marginally higher viral loads than coinfections (P = 0.051). All except one sample had E2 disruption restricted to only a part of the gene. Integration is a critical step in HPV-52-induced carcinogenesis. The profile of E2 disruption was different from that described for HPV-16, with the amino-terminal region being most frequently involved. Selecting the appropriate E2 region for amplification is critical in studying the integration of HPV-52. In summary, the HPV-52 viral load and the integrated proportion increased with the severity of the cervical lesions but had a different pattern than that of HPV-16.
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PMID:Increase of integration events and infection loads of human papillomavirus type 52 with lesion severity from low-grade cervical lesion to invasive cancer. 1827 18

Chronic and persistent inflammation contributes to cancer development and can predispose to carcinogenesis. Infection-driven inflammations are involved in the pathogenesis of approximately 15-20% of human tumors. However, even tumors that are not epidemiologically linked to pathogens are characterized by the presence of an inflammatory component in their microenvironment. Hallmarks of cancer-associated inflammation include the presence of infiltrating leukocytes, cytokines, chemokines, growth factors, lipid messengers, and matrix-degrading enzymes. Schematically, two interrelated pathways link inflammation and cancer: (1) genetic events leading to neoplastic transformation promote the construction of an inflammatory milieu; (2) tumor-infiltrating leukocytes, in particular macrophages, are prime regulators of cancer inflammation. Thus, an intrinsic pathway of inflammation (driven in tumor cells), as well as an extrinsic pathway (in tumor-infiltrating leukocytes) have been described and both contribute to tumor progression.
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PMID:Pathways connecting inflammation and cancer. 1832 55

Cervical cytology screening has reduced cervical cancer morbidity and mortality but shows important shortcomings in terms of sensitivity and specificity. Infection with distinct types of human papillomavirus (HPV) is the primary etiologic factor in cervical carcinogenesis. This causal relationship has been exploited for the development of molecular technologies for viral detection to overcome limitations linked to cytologic cervical screening. HPV testing has been suggested for primary screening, triage of equivocal Pap smears or low-grade lesions and follow-up after treatment for cervical intraepithelial neoplasia. Determination of HPV genotype, viral load, integration status and RNA expression could further improve the effectiveness of HPV-based screening and triage strategies. The prospect of prophylactic HPV vaccination stresses the importance of modification of the current cytology-based screening approach.
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PMID:Human papillomavirus in cervical cancer screening: important role as biomarker. 1839 22

Despite the progress in cancer therapeutics and chemotherapy development with the introduction of new drugs, advanced gastric cancer continues to have an extremely poor prognosis and with limited treatment options. The introduction of new antitarget drugs has introduced a new perspective in cancer treatment in general and gastric cancer in particular. Nevertheless, few studies have been developed with this generation of drugs. The monoclonal antibody antiepidermal growth factor receptor (EGFR) cetuximab and the antiangiogenic bevacizumab have been used in phase I and II studies with good results, which need to be confirmed in new phase III studies. The carcinogenesis of this tumor provides information regarding two transcription and signaling pathways of great interest and with therapeutic potential. Infection by Helicobacter pylori is recognized as the cause of gastric cancer development, and there are two elements that play an important role in this process: the CagA gene, whose protein is introduced in the cell by H. pylori initiates the process; and the hedgehog signaling pathway, which regulates the gastric mucosa and is very frequently activated in gastric cancer. Taking action on these agents may be a new and effective method of treating gastric cancer, and therefore must be researched.
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PMID:New drugs in the treatment of gastric tumors. 1849 Feb 41


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