Effects of Ritonavir on HHV-8 vGPCR signaling and tumorigenesis

描述(申请人提供)：人类疱疹病毒8型(HHV-8)是卡波西肉瘤(KS)的主要病原体，编码vGPCR，是人IL-8受体的同源物，是G蛋白偶联受体(GPCR)家族的成员。VGPCR由HHV-8开放阅读框74编码，激活转录因子NFkappaB和NF-AT，并诱导受这些因子调控的细胞因子和细胞表面黏附分子的表达。在TG小鼠体内表达vGPCR会导致KS样肿瘤，我们从其中一个肿瘤中获得了一种细胞系，该细胞系在裸鼠体内保留了vGPCR的表达和致瘤性。我们之前已经证明，利托那韦是一种用于治疗HIV感染的蛋白酶抑制剂，它可以抑制NFkappaB的激活。初步研究表明，利托那韦也能抑制核因子-AT的激活。利托那韦使用人KS来源的HHV-8阴性细胞株抑制裸鼠异种移植模型中的肿瘤形成。我们建议表征利托那韦抑制vGPCR介导的信号转导和肿瘤发生的机制。这些研究将包括确定利托那韦抑制NFkappaB和NF-AT激活的信号通路，以及确定利托那韦抑制NFkappaB和/或NF-AT激活是否抑制vGPCR依赖的裸鼠肿瘤形成。这些研究将显示利托那韦是否在体外和体内阻断HHV-8vGPCR的活性，以及它是否具有独立于其抗逆转录病毒活性的抗KS活性。因此，这一结果可能为开发新的KS治疗替代方案提供理论依据。这些发现可能对其他癌症具有更广泛的适用性。

DESCRIPTION (provided by applicant): Human herpesvirus 8 (HHV-8), the primary etiologic agent of Kaposi's sarcoma (KS), encodes vGPCR, a homologue of the human IL-8 receptor and a member of the G protein coupled receptor (GPCR) family. vGPCR, encoded by HHV-8 open reading frame 74, activates transcription factors including NFkappaB and NF- AT and induces expression of cytokines and cell surface adhesion molecules regulated by these factors. Expression of vGPCR in Tg mice causes KS-like tumors, and we have derived a cell line from one of these tumors that retains expression of vGPCR and tumorigenicity in nude mice. We have previously shown that ritonavir, a protease inhibitor used to treat HIV infection, inhibits NFkappaB activation. Preliminary studies suggest that ritonavir also inhibits NF-AT activation. Ritonavir inhibits tumorigenesis in a nude mouse xenotransplant model using human KS-derived HHV-8-negative cell lines. We propose characterizing the mechanisms of inhibition by ritonavir of vGPCR-mediated signaling and tumorigenesis. These studies will include identifying the signaling pathways through which ritonavir inhibits NFkappaB and NF-AT activation and determining whether inhibition of NFkappaB and/or NF-AT activation by ritonavir inhibits vGPCR-dependent tumorigenesis in nude mice. These studies will show whether ritonavir blocks the activities of HHV-8 vGPCR in vitro and in vivo and whether it has an anti-KS activity independent of its anti-retro viral activity. Consequently, the results may provide a rationale for developing new therapeutic alternatives for KS. The findings could have a more general applicability to other cancers.