Cooperative roles of Tat & k-cyclin Kaposi's sarcoma

描述(申请人提供)：卡波西肉瘤是一种内皮来源的恶性肿瘤，也是艾滋病患者中最常见的癌症。60%与艾滋病相关的KS开始于口腔，这是一个严重的口腔健康问题。尽管人类疱疹病毒8型(HHV-8)被确认为所有形式的KS的病原体，但KS在HIV感染患者中的异常高患病率表明HIV和HHV-8在KS的发展过程中存在协同作用。HIV Tat是病毒基因表达的关键调控因子之一，在HIV相关致病机制中发挥着重要作用。TAT导致培养的内皮细胞功能障碍和转化，并在转基因动物中诱导KS样病变。HHV-8K-Cyclin是细胞周期蛋白D的同系物，通过异常激活CDK6，加速细胞周期的G1/S转换，扰乱细胞生长控制。K-Cyclin的表达促进内皮细胞的增殖。我们已经发现TAT在体内与k-Cyclin相互作用，为HIV和HHV-8之间的病理联系提供了证据。在这里，我们建议利用永生化的原代内皮细胞来研究TAT和k-Cyclin在KS发生中的协同作用。利用这个体外模型，我们将解剖导致HHV-8感染的内皮细胞向KS恶性发展的步骤。其具体目的是：(1)确定TAT和k-Cyclin之间的分子相互作用，并检测与这两种蛋白相关的激酶活性；(2)确定TAT和k-Cyclin在促进内皮细胞增殖中的协同作用；(3)证明TAT在促进HHV-8感染和HHV-8诱导的细胞转化中的作用。这些研究将增加我们对艾滋病相关KS的发病机制、TAT和k-Cyclin的协同作用的理解，并提出抗击这种肿瘤的策略。

DESCRIPTION (provided by applicant): Kaposi's sarcoma is a malignant tumor of endothelial origin and the most frequent cancer in AIDS patients. Sixty percent of AIDS-associated KS initiate in the oral cavity, representing a serious problem in oral health. Despite identification of human Herpesvirus 8 (HHV-8) as the etiological agent for all forms of KS, the extraordinarily higher prevalence of KS in HIV-infected patients suggests a cooperative interaction between HIV and HHV-8 in the development of KS. HIV Tat is one of the key regulating factors for viral gene expression and plays many roles in HIV-associated pathogenesis. Tat causes dysfunction and transformation of cultured endothelial cells and induces KS-like lesions in transgenic animals. HHV-8 k-cyclin, a homologue of cellular cyclin D, disrupts cell growth control by aberrantly activating Cdk6 and accelerating the G1/S transition of the cell cycle. The expression of k-cyclin promotes proliferation of endothelial cells. We have found that Tat interacts with k-cyclin in vivo, providing evidence of pathological links between HIV and HHV-8. Here, we propose to study the cooperative roles of Tat and k-cyclin in the development of KS by using immortalized primary endothelial cells. Using this in vitro model, we will dissect steps that are responsible for the HHV-8-infected endothelial cells to progress toward the development of KS malignancy. The specific aims are: (1) define the molecular interaction between Tat and k-cyclin and examine kinase activities associated with these two proteins, (2) determine cooperative effects of Tat and k-cyclin in promoting the proliferation of endothelial cells, (3) demonstrate roles of Tat in enhancing HHV-8 infection and HHV-8-induced cell transformation. These studies will increase our understanding of the pathogenesis of AIDS-associated KS, the cooperative role of Tat and k-cyclin, and suggest a strategy in combating this tumor.