Lipid Metabolism and KSHV-associated Lymphoma Pathogenesis

描述（由申请方提供）：卡波西肉瘤相关疱疹病毒（KSHV）是优先在免疫受损宿主（包括感染HIV的患者）中发生的癌症的病原体。这些癌症之一，称为原发性渗出性淋巴瘤（PEL）的克隆B细胞恶性肿瘤，与显著的死亡率相关，目前没有有效的治疗方法来减少PEL的进展或延长生存期。PEL的发病机制涉及KSHV基因表达和激活特异性信号转导通路，从而诱导肿瘤细胞增殖和延长存活。因此，开发针对KSHV特异性激活的这些途径的新型化合物可能会为PEL提供更有效和安全的治疗选择。具有生物活性的鞘脂在许多生理过程中发挥重要作用，但与鞘氨醇激酶（SK）的作用和鞘氨醇-1-磷酸（S1 P）的产生相关的异常鞘脂代谢也有助于癌症的进展。我们已经产生了一种活性化合物，ABC 294640，它特异性靶向多种SK亚型，并有效地削弱S1 P介导的信号转导，同时在体外和体内诱导肿瘤细胞死亡。由于ABC 294640抑制与PEL发病机制相关的信号转导，我们进行了初步研究以确定ABC 294640是否抑制PEL细胞生长。我们的体外研究表明，ABC 294640选择性抑制KSHV感染的淋巴瘤细胞生长，但不抑制KSHV阴性淋巴瘤细胞的生长。这些数据补充了我们的额外数据，其中ABC 294640在KSHV感染的原代细胞中诱导凋亡，而不是未感染的细胞。此外，ABC 294640诱导已知在其他癌细胞系中诱导凋亡的神经酰胺-脂质部分的剂量依赖性增加。ABC 294640还上调凋亡前JNK活化，同时减少PEL细胞中的组成性NF-κ B活化，这两个事件先前与癌细胞凋亡的起始有关。最后，ABC 294640诱导了PEL细胞中的裂解性KSHV基因表达，这是一个已知导致细胞死亡的过程。因此，我们假设ABC 294640通过神经酰胺的积累和/或诱导裂解性KSHV基因表达和下游促凋亡信号传导优先诱导PEL细胞的凋亡和细胞死亡，并且ABC 294640减少体内PEL的进展。为了评价全身给予ABC 294640在体内减少PEL形成的可行性并更好地理解ABC 294640如何选择性靶向KSHV感染的细胞，我们提出了三个目标：1）合成足够量的ABC 294640用于体内研究; 2）评价ABC 294640抑制免疫缺陷小鼠中PEL形成的能力;和3）确定ABC 294640减少KSHV感染的细胞生长和存活的机制。通过完成这些研究，我们希望能够进行临床试验，以评估ABC 294640给药在HIV感染的PEL患者中的疗效和安全性。我们额外的机制研究也应该为未来的研究提供进展，以解决ABC 294640在选择性靶向病毒感染细胞中的作用。 公共卫生相关性：与卡波西肉瘤相关疱疹病毒（KSHV/HHV 8）病因相关的肿瘤，包括原发性渗出性淋巴瘤（PEL），是HIV相关疾病之一，预示着HIV感染患者的预后不良。目前的PEL疗法是无效的，并产生显著的毒性。因此，在动物模型中对抑制PEL细胞生长并选择性靶向KSHV感染细胞的有前景的化合物进行临床前测试将为在将来的PEL临床试验中测试这些化合物提供基础。

DESCRIPTION (provided by applicant): The Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of cancers arising preferentially within immune compromised hosts, including patients infected with HIV. One of these cancers, a clonal B-cell malignancy known as primary effusion lymphoma (PEL), is associated with significant mortality, and there are currently no effective therapies for reducing the progression of PEL or prolonging survival. Pathogenesis of PEL involves KSHV gene expression and activation of specific signal transduction pathways which induce proliferation and prolong survival of tumor cells. Therefore, the development of novel compounds targeting these pathways specifically activated by KSHV may result in more effective and safe treatment options for PEL. Bioactive sphingolipids play an important role in many physiologic processes, but aberrant sphingolipid metabolism related to the action of sphingosine kinase (SK) and the generation of sphingosine-1-phosphate (S1P) also contribute to cancer progression. We have generated an active compound, ABC294640, that specifically targets multiple SK isoforms and effectively impairs S1P- mediated signal transduction while inducing tumor cell death in vitro and in vivo. With the knowledge that ABC294640 inhibits signal transduction relevant to PEL pathogenesis, we performed preliminary studies to determine whether ABC294640 inhibits PEL cell growth. Our in vitro studies revealed that ABC294640 selectively inhibits KSHV-infected lymphoma cell growth but not the growth of KSHV-negative lymphoma cells. These data compliment our additional data wherein ABC294640 induces apoptosis in KSHV-infected primary cells but not uninfected cells. Moreover, ABC294640 induced a dose-dependent increase in ceramides-lipid moieties known to induce apoptosis in other cancer cell lines. ABC294640 also upregulated proapoptotic JNK activation while reducing constitutive NF-kB activation in PEL cells, two events previously implicated in the initiation of cancer cell apoptosis. Finally, ABC294640 induced lytic KSHV gene expression in PEL cells-a process known to cause cell death. Therefore, we hypothesize that ABC294640 induces apoptosis and cell death preferentially in PEL cells through the accumulation of ceramides and/or the induction of lytic KSHV gene expression and downstream proapoptotic signaling, and that ABC294640 reduces progression of PEL in vivo. To evaluate the feasibility of reducing PEL formation in vivo with the systemic administration of ABC294640 and to better understand how ABC294640 selectively targets KSHV-infected cells, we propose three aims: 1) to synthesize sufficient amounts of ABC294640 for in vivo studies; 2) to evaluate the ability of ABC294640 to inhibit PEL formation in immune deficient mice; and 3) to determine mechanisms for ABC294640 reduction of KSHV-infected cell growth and survival. Through the completion of these studies, we hope to move toward the performance of clinical trials to evaluate the efficacy and safety of ABC294640 administration in HIV-infected patients with PEL. Our additional mechanistic studies should also provide inroads for future studies to address the role of ABC294640 in selectively targeting virus-infected cells. PUBLIC HEALTH RELEVANCE: Tumors etiologically linked to the Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8), including primary effusion lymphoma (PEL), are among those HIV-associated illnesses which portend a poor prognosis for HIV-infected patients. Current PEL therapies are not efficacious and incur significant toxicity. Therefore, preclinical testing of promising compounds in animal models which inhibit PEL cell growth and which selectively target KSHV-infected cells would provide a basis for testing these compounds in future clinic trials for PEL.