The dysregulation of the molecular events governing cell cycle control is emerging as a central theme of oral carcinogenesis. Regulatory pathways responding to extracellular signaling or intracellular stress and DNA damage converge on the cell cycle apparatus. Abrogation of mitogenic and anti-mitogenic response regulatory proteins, such as the retinoblastoma tumor suppressor protein (pRB), cyclin D1, cyclin-dependent kinase (CDK) 6, and CDK inhibitors (p21(WAF1/CIP1), p27(KIP1), and p16(INK4a)), occur frequently in human oral cancers. Cellular responses to metabolic stress or genomic damage through p53 and related pathways that block cell cycle progression are also altered during oral carcinogenesis. In addition, new pathways and cell cycle regulatory proteins, such as p12(DOC-1), are being discovered. The multistep process of oral carcinogenesis likely involves functional alteration of cell cycle regulatory members combined with escape from cellular senescence and apoptotic signaling pathways. Detailing the molecular alterations and understanding the functional consequences of the dysregulation of the cell cycle apparatus in the malignant oral keratinocyte will uncover novel diagnostic and therapeutic approaches. (+info)
Modulation of apoptosis by human papillomavirus (HPV) oncoproteins.
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The regulation of host-mediated apoptosis by the E6 and E7 oncoproteins has garnered attention because it is believed to be an important strategy employed by high-risk (HR)-human papillomaviruses (HPVs) to evade immune surveillance. Additionally, the revelation that E5 can protect cells from tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis suggests that it may also play a role in undermining host defense mechanisms. Cellular transformation is an unintended consequence of persistent infection by HR-HPVs, and it is therefore likely that the primary function of E5, E6 and E7 is to regulate cell survival throughout the normal viral life cycle in order to ensure viral replication and promote the spread of progeny. The purpose of this article is to review the literature on the regulation of host-mediated apoptosis by E5, E6 and E7 that describes the mechanisms employed by HR-HPVs to persist in the host and create the conditions necessary for cellular transformation. (+info)
Vaccines for the prevention of human papillomavirus infections.
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Human papillomavirus (HPV) infection is the known cause of almost all cases of cervical cancer. An understanding of the HPV genome has allowed the development of two prophylactic vaccines capable of protecting against both persistent HPV infection and cervical intraepithelial neoplasia (CIN) with 100% efficacy in fully vaccinated women. The vaccines, manufactured by Merck (Gardasil, which was approved by the US FDA in June, 2006) and GlaxoSmithKline (Cervarix, which will be submitted for US FDA approval by the end of 2006), both target HPV types 16 and 18, which together account for 70% of cervical cancer. Merck vaccine also targets HPV 6 and 11, covering =90% of genital warts. These vaccines are highly immunogenic and have an excellent safety profile. HPV vaccines promise to offer an exciting contribution to healthcare and cancer prevention. However, many questions remain concerning who to vaccinate, the duration of protection, cost, public acceptance, and the potential for worldwide distribution. (+info)
Prevalence of human papillomavirus (HPV) in oral cavity and oropharynx.
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The prevalence of human papillomavirus (HPV) in the oral cavity and oropharynx has not yet been as well studied as its infection of the vaginal tract. However, new study are emerge after the development of molecular biology techniques. The objective of this study is to show the prevalence of HPV in the oral cavity and the oropharynx. An ample bibliographic review was done showing a prevalence of HPV 6, 11 in a normal oral mucous membrane (latent infection). In oral benign lesions associated with HPV, a prevalence of HPV 6 and 11 was observed in squamous cell papilloma (SCP) and condylomas acuminatum, while HPV 2 and 57 were more prevalent in verruca vulgaris lesions. As for focal epithelial hyperplasia (FEH) and oral cancer, especially squamous cell carcinoma (SCC), the prevalence was of HPV 13 and 32, and HPV 16, respectively. The last findings are, nonetheless, controversial. The last findings are, nonetheless, controversial. Showed also discrepancy result the prevalence of human papillomavirus (HPV) in normal oral mucous (latent infection) and in oral cancer, however evidenced confirmatory result in oral benign lesions associated with virus. (+info)
Epidemiology and natural history of human papillomavirus infections in the female genital tract.
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Human papillomavirus (HPV) is the most common newly diagnosed sexually transmitted infection in the United States. Although the majority of sexually active adults will be infected with HPV at least once in their lives, it is sexually active women less than 25 years of age who consistently have the highest rates of infection. Besides youth and gender, common risk factors for HPV infection and clinical sequelae of infection include high number of sexual partners and coinfection with Chlamydia trachomatis or herpes simplex virus. Most HPV infections are cleared by the immune system and do not result in clinical complications. Clinical sequelae in cases of low-risk HPV infection consist of genital warts, and clinical manifestations of high-risk HPV infection include abnormal Pap test results, low-grade squamous intraepithelial lesions (LSIL), high-grade squamous intraepithelial lesions (HSIL), and cervical cancer. LSIL, HSIL, and cervical cancer carry significant morbidity and/or mortality; genital warts and abnormal Pap test results are often significant sources of psychosocial distress. Currently, there are neither effective means of preventing HPV transmission nor cures for clinical manifestations: infection can only be prevented via complete sexual abstinence, while treatment for clinical sequelae such as genital warts and cytologic abnormalities consists of removing the problematic cells and watching for recurrence; this method consumes significant health care resources and is costly. New prophylactic HPV vaccines promise to dramatically reduce the incidence of HPV infection, genital warts, and cytologic abnormalities. (+info)
Reducing the health burden of HPV infection through vaccination.
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Human papillomavirus (HPV), a sexually transmitted infection and the etiologic cause of genital warts and cervical cancer, is highly prevalent in sexually active men and women. Although cervical screening procedures have significantly reduced the disease burden associated with HPV infection, they are expensive and abnormal results cause significant emotional distress. Therefore, prevention may be an effective strategy for reducing the economic, psychosocial, and disease burden of HPV infection. Multivalent vaccines are now in clinical development. A bivalent vaccine that protects against HPV 16 and 18, and a quadrivalent vaccine which protects against HPV types 6, 11, 16, and 18, have been shown to significantly reduce the occurrence of incident and persistent HPV infections in phase 2 clinical trials; phase 3 trials are currently underway. HPV vaccines will be most effective when administered prior to initiation of sexual activity, and vaccination campaigns should aggressively target preadolescent and adolescent populations. (+info)
E6/E7 expression of human papillomavirus type 20 (HPV-20) and HPV-27 influences proliferation and differentiation of the skin in UV-irradiated SKH-hr1 transgenic mice.
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The functional role of UV irradiation, in combination with the E6 and E7 proteins of the cutaneous human papillomavirus (HPV) types in the malignant conversion of benign papillomatous lesions, has not been elucidated. Transgenic SKH-hr1 hairless mice expressing HPV-20 and HPV-27 E6 and E7 proteins in the suprabasal compartment were generated and exposed to chronic UV irradiation. Histological and immunohistochemical examination of skin samples revealed enhanced proliferation of the epidermal layers and papilloma formation in both transgenic strains in comparison to what was observed with nontransgenic mice. Squamous cell carcinoma developed in the HPV-20 E6/E7 transgenic line as well as in the HPV-27 E6/E7 transgenic line. Several weeks after cessation of UV-B exposure, enhanced proliferation, as measured by BrdU incorporation, was maintained only in HPV-20 transgenic skin. Keratin 6 expression was increased in the transgenic mice throughout all cell layers. Expression of the differentiation markers involucrin and loricrin was reduced and disturbed. p63alpha expression was differentially regulated with high levels of cytoplasmic expression in clusters of cells in the granular layer of the skin in the transgenic lines 20 weeks after cessation of UV-B exposure, in contrast to uninterrupted staining in the nontransgenic lines. p53 was expressed in clusters of cells in nontransgenic and HPV-27 transgenic mice, in contrast to an even distribution in a higher number of cells in HPV-20 transgenic animals. (+info)
Human papilloma virus and p53 expression in bladder cancer in Egypt: relationship to schistosomiasis and clinicopathologic factors.
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The aim of the current study was to compare the role of p53 and human papillomavirus (HPV) in schistosomiasis-related and schistosomiasis-unrelated carcinoma of the urinary bladder. To achieve this aim, we investigated 114 bladder carcinomas for p53 oncoprotein expression by immunohistochemistry and for human papillomavirus by in situ hybridization technique. The results revealed that 64 tumors (56.1%) were schistosomiasis-associated. Sixty seven (58.8%) were transitional cell carcinomas and 32 (28%) were squamous cell carcinomas. The remaining 15 tumors (13.2%) included adenocarcinomas and sarcomatoid carcinomas. In both schistosomiasis-associated and non-associated carcinomas, p53 oncoprotein expression was significantly higher in poorly differentiated tumors. However, it was significantly higher in locally more invasive tumors in the schistosomal carcinomas only. HPV types 16/18 could be detected in 1 of the 114 bladder carcinomas (0.95%), which was schistosomiasis-related squamous cell carcinoma in situ. These results suggest that p53 immunohistochemistry can be a prognostic factor in both schistosomal and nonschistosomal bladder cancer. More importantly, HPV does not seem to play a role in the pathogenesis of either type of bladder cancer in our country. (+info)