Cervical Cancer Cofactors and HPV DNA Integration

描述(申请人提供)：人乳头瘤病毒(HPV)感染宫颈可导致鳞状上皮内病变(SIL)，可通过增加分化程度较低的阶段而进展，从而导致宫颈癌(CaCx)。绝大多数CaCx与高危HPV类型有关。HPV-16通过HPV E6干扰抑癌蛋白P53的功能，通过HPV E7蛋白干扰pRb的功能。HPV-16癌蛋白取消这些活性会导致突变的积累，最终导致CaCx。SIL向CaCx发展的早期事件尚不清楚。然而，很明显，病毒基因组物理状态的变化(从外体到整合体)可能会加速CaCx的发育。整合病毒DNA的转录本比异体病毒DNA的转录本更稳定，在整合序列的细胞中病毒癌蛋白水平更高。HPV-16的转录本是多顺反子的，所有早期的mRNAs都含有E7和E5序列。整合后，E5序列通过病毒基因组与宿主序列的融合而丢失。我们已经开发了一种简单的PCR测试来区分从ThlnPrep巴氏涂片的残留液中提取的RNA上的整合序列或附体序列获得的转录本。只有一小部分患有sIL的女性会患上CaCx。人们已经认识到，辅因与CaCx的风险增加有关。这些因素包括吸烟、亚甲基四氢叶酸还原酶(MTHFR)基因多态性、HPV-16变异、脆性组氨酸三联体(FHIT)基因表达缺失和沙眼衣原体感染。由于病毒基因组整合到宿主基因组是癌症进展的核心，那么具有一个或多个这些危险因素的女性应该在sIL中整合病毒DNA。我们已经证明，与E7转录本相比，大约22%含有HPV-16E7 RNA的ASCUS(意义不明的异常鳞状细胞)女性具有基于E5转录本缺失或低水平的整合序列。我们假设具有完整HPV-16序列的女性具有与宫颈癌风险增加相关的更多风险因素之一。整合如何通过这些辅助因子发生的机制尚不清楚。我们建议对携带整合DNA的女性的风险因素进行检测，以确定其中一个风险因素的存在是否与整合序列有关。这种联系将导致实验室研究宿主和病毒基因组之间的相互作用，让我们更好地了解导致恶性转化的事件。

DESCRIPTION (provided by applicant): Human papillomavirus (HPV) infection of the cervix can result in a squamous intraepithelial lesion (SIL) that can progress through increasing less differentiated stages giving rise to cervical cancer (CaCx). The vast majority of CaCx are associated with high risk HPV types. HPV-16 perturbs the function of the tumor suppressor proteins p53 by HPV E6 and pRB by HPV E7 proteins. Abrogation of these activities by HPV-16 oncoproteins can result in the accumulation of mutations and eventually CaCx. Early events in the progression of SIL to CaCx are not well understood. However, it is clear that a change in the physical state of the viral genome (episomal to integrated) likely precipitate CaCx development. Transcripts from integrated virus DNA are more stable than those from episomal virus DNA and the level of viral oncoproteins is higher in cells with integrated sequences. Transcripts of HPV-16 are polycistronic and all early mRNAs contain E7 and E5 sequences. After integration the E5 sequences are lost through fusion of the viral genome with host sequences. We have developed a simple PCR test to distinguish transcripts obtained from integrated or episomal sequences on RNA extracted from residual PreservCyt fluid of the ThlnPrep Pap smear. Only a small percentage of women with SIL will develop CaCx. It has been recognized that cofactors are associated with increased risk for CaCx. These include smoking, methylenetetrahydrofolate reductase (MTHFR) polymorphism, HPV-16 variants, loss of fragile histidine triad (FHIT) gene expression and ChIamydia trachomatis infection. Since integration of the viral genome into the host genome is central to progression to cancer, then women with one or more of these risk factors should have integrated virus DNA in SIL. We have shown that about 22% of women with ASCUS (abnormal squamous cells of undetermined significance) that contain HPV-16 E7 RNA have integrated sequences based on the absence or low levels of E5 transcripts compared to E7 transcripts. We hypothesize that women with integrated HPV-16 sequences have one of more risk factors that are associated with increased risk for cervix cancer. The mechanism of how integration occurs through these cofactors is unknown. We propose to assay for risk factors in women with integrated versus episomal DNA to determine whether the presence of one of more risk factors is associated with integrated sequences. An association will lead to laboratory studies investigating interactions between host and viral genomes giving us a better understanding of events leading to malignant transformation.