miRNAs have emerged as master regulators of cancer-related events. miRNA dysregulation also occurs in Kaposi sarcoma (KS). Exploring the roles of KS-associated miRNAs should help to identify novel angiogenesis and lymphangiogenesis pathways. In the present study, we show that Kaposi sarcoma-associated herpesvirus (KSHV), the etiological agent of KS, induces global miRNA changes in lymphatic endothelial cells (LECs). Specifically, the miR-221/miR-222 cluster is down-regulated, whereas miR-31 is upregulated. Both latent nuclear antigen (LANA) and Kaposin B repress the expression of the miR-221/miR-222 cluster, which results in an increase of endothelial cell (EC) migration. In contrast, miR-31 stimulates EC migration, so depletion of miR-31 in KSHV-transformed ECs reduces cell motility. Analysis of the putative miRNA targets among KSHV-affected genes showed that ETS2 and ETS1 are the downstream targets of miR-221 and miR-222, respectively. FAT4 is one of the direct targets of miR-31. Overexpression of ETS1 or ETS2 alone is sufficient to induce EC migration, whereas a reduction in FAT4 enhances EC motility. Our results show that KSHV regulates multiple miRNAmRNA networks to enhance EC motility, which eventually contributes to KS progression by promoting the spread of malignant KS progenitor cells. Targeting
IntroductionKaposi sarcoma-associated herpesvirus (KSHV) was identified in 1994. 1 KSHV is also associated with 2 other human B-cell leukemias, primary effusion lymphoma (PEL) and multicentric Castleman disease. 2 Kaposi sarcoma (KS) is one of the few human cancers derived from a lymphatic endothelial cell (LEC) lineage, 3,4 and typically appears as colored lesions or patches on the skin, although it can spread to internal organs. 2 This disease has been recognized as a highly disseminated and angiogenic tumor. 4 Analyzing KSHV clonality at different stages of KS has shown that KS begins as a polyclonal disease and then evolves into a mono/oligoclonal disease involving infected spindle cells. 5 This model therefore implies that the spreading of a few malignant spindle cells in patients' bodies occurs during tumor progression. Moreover, distal metastasis, such as pulmonary KS, can be observed in AIDS-KS patients and causes diffused lung disease. Tumor cells of KSHV-associated B-cell neoplasias (PEL and multicentric Castleman disease) are also able to migrate into body cavities. 6 The ability of KSHV to induce cell migration and invasion is therefore important to disease progression.In vitro, KSHV infects both micro-and macrovascular endothelial cells (ECs), and these cells are useful when studying the role of KSHV in the pathogenesis of KS. 7,8 KSHV has also become a powerful tool that aids in the study of EC biology. 9 KSHV infects both LECs and blood vessel ECs (BECs) of microvascular origin in vitro. 3,4 After infection, KSHV stimulates EC invasiveness by inducing extracellular matrix metalloproteinases (MMPs) such as MMP-1, MMP-2, and MMP-9. 10 Because the majority of cells in KS lesions and in KSHV-infected...
