ROLE OF Rac AND REACTIVE OXYGEN SPECIES IN KAPOSI'S SARCOMA VIRAL ONCOGENESIS

描述(申请人提供)：卡波西肉瘤(KS)，由卡波西肉瘤相关疱疹病毒(KSHV)引起，是一种与艾滋病相关的主要癌症，是全球卫生挑战。肿瘤的特点是强烈的血管生成和梭形细胞的增殖，这些细胞可以影响皮肤、粘膜和内脏，导致显著的发病率。了解病毒和细胞基因导致KS癌变的作用对于开发合理设计的KS治疗方法至关重要。Mesri和Goldschmidt实验室之间的合作导致了rac1 GTPase的确定，该酶是一种信号媒介，可以触发非吞噬细胞NADPH-氧化酶(NOX)产生活性氧物种(ROS)，是KS中潜在的主要参与者。我们发现，在转基因小鼠中，由平滑肌肌动蛋白(-SMA)启动子驱动的结构性活性rac1突变体(RACCA)的表达导致了与卡波西肉瘤非常相似的病变的形成。值得注意的是，Racca-SMA肿瘤与KS肿瘤活检组织显示主要的转录组重叠。Racca肿瘤的发生与男性有关，并涉及血管生成和细胞增殖的ROS激活。此外，我们还发现我们的KS小鼠模型的AIDS-KS皮损和KSHV感染的肿瘤(小鼠内皮细胞KSHV Bac36-mECK36)在所有KSHV感染的(LANA+Ve)细胞中都过表达rac1。此外，我们发现KS病变和mECK36病变过度表达NOX家族的关键成员，并且mECK36肿瘤以KSHV依赖的方式上调NOX成员。这导致我们测试了N-乙酰半胱氨酸(NAC)--一种具有良好特性的抗氧化剂--抑制小鼠mECK36肿瘤的能力。我们发现NAC可以阻止KSHV诱导的肿瘤形成。有趣的是，我们还发现NAC通过与血小板衍生生长因子(PDGF)受体和配体下调有关的机制来抑制mECK36肿瘤中的VEGF、c-myc和病毒基因的表达。这些数据表明，rac1、NOx、ROS及其下游效应分子都是积极参与KS病毒致癌的分子，并提示rac1信号和氧化应激可能是诱人的KS化学预防和治疗靶点。我们建议：研究Rac1激活在KSHV肿瘤发生中的机制和作用(目标1)，研究ROS的NADPH氧化酶诱导在KSHV肿瘤发生中的作用(目标2)，并测试药物ROS抑制在预防和治疗RaccA和KSHV诱导的肿瘤中的效果(目标3)。

DESCRIPTION (provided by applicant): Kaposi's sarcoma (KS), caused by the Kaposi's sarcoma-associated herpes virus (KSHV), is a major cancer associated with AIDS and a global health challenge. The tumor is characterized by intense angiogenesis and the proliferation of spindle cells that can affect the skin, mucosa and viscera, causing significant morbidity. Understanding the role of viral and cellular genes leading to KS carcinogenesis is paramount to developing rationally designed therapies for KS. A collaboration between the Mesri and Goldschmidt labs has led to the identification of the Rac1 GTPase, a signaling mediator that triggers production of reactive oxygen species (ROS) by non-phagocytic NADPH-oxidase (NOX), as a potential major player in KS. We have found that expression of a constitutively-active Rac1 mutant (RacCA) driven by -smooth muscle actin (-SMA) promoter in transgenic mice led to the formation of lesions that strongly resemble those of Kaposi's sarcoma. Significantly, RacCA--SMA tumors revealed major transcriptome overlap with KS tumor biopsies. RacCA tumorigenesis was linked to male gender, and involved ROS activation of angiogenesis and cell proliferation. Furthermore, we found that AIDS-KS lesions and KSHV-infected tumors from our KS mouse model (mouse endothelial cell KSHV Bac36- mECK36) over-express Rac1 in all KSHV-infected (LANA+ve) cells. Moreover, we found that KS lesions and mECK36 lesions over-express key members of the NOX family and that mECK36 tumors upregulate NOX members in a KSHV dependent fashion. This led us to test the ability of N-acetyl cysteine (NAC), a well characterized antioxidant, to suppress mECK36 tumors in mice. We found that NAC prevented KSHV-induced tumor formation. Interestingly, we also found that NAC inibited VEGF, c-myc and viral gene expression in the mECK36 tumors through a mechanism involving platelet derived growth factor (PDGF) receptor and ligand downregulation. These data indicate that Rac1, NOX, ROS, and their downstream effectors are molecules actively involved in KS viral oncogenesis, and suggest that Rac1 signaling and oxidative stress could be attractive KS chemopreventive and therapeutic targets. We proposse to: Study mechanisms and role of Rac1 activation in KSHV oncogenesis (Aim 1), study the role of NADPH oxidase induction of ROS in KSHV oncogenesis (Aim 2) and to test the efficacy of pharmacologic ROS inhibition on prevention and treatment of RacCA and KSHV-induced tumors (Aim 3).