Anti-nucleolin aptamer AS1411: Applications in Kaposi's Sarcoma Associated Herpes Virus (KSHV) biology

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Kaposi’s sarcoma-associated herpesvirus (KSHV), a member of the human γ-herpesvirus family is also termed as human herpesvirus type 8 (HHV-8). KSHV is an etiological agent of an endothelial tumor called Kaposi’s sarcoma (KS) and a highly aggressive lymphoproliferative B cell lymphoma called primary effusion lymphoma (PEL). KS is the most common vascular malignancy causing high morbidity and mortality in HIV-infected patients. PEL is a rare tumor of hematopoietic and lymphoid tissues and is associated with a poor prognosis. PEL cases have been dramatically reduced in the US since the widespread use of combined antiretroviral therapy (cART) but KSHV still causes significant mortality in the developing world. There is a critical need in KSHV targeting specific antiviral drugs, which are very well tolerated with no severe adverse events for immunocompromised patients with KSHV associated malignancies. KSHV exhibits two distinct phases in its life cycle. During latency, a minimal number of latency genes such as vFLIP (ORF71), vCyclin (ORF72), latency-associated nuclear antigen-1 (LANA-1; ORF73), and Kaposin are expressed. By contrast, during the lytic phase, KSHV expresses a wide array of immediate-early (IE), delayed-early (DE), and late genes; undergo active replication and produce virion progeny. KSHV has been shown to utilize multiple host growth factors, cytokines, angiogenic factors, and cell signaling and metabolism-related proteins for creating a beneficial environment for its replication, survival, and latency. Our exciting studies discovered that: 1) KS skin lesions express remarkably robust expression of nucleolin compared to healthy skin tissue; 2) KSHV de novo infection in primary endothelial cells induced a high level of nucleolin and phospho-nucleolin, and more importantly, 3) Incubation of KSHV infected cells with G- quadruplex forming anti-nucleolin aptamer AS1411 reduced KSHV latent (ORF73) and increased lytic (ORF50) gene expression and we obtained similar results in nucleolin silenced KSHV infected PEL cells. 4) AS1411 treatment was efficacious in inducing cell death in KSHV infected PEL cell lines. Based on our preliminary results, we hypothesize that KSHV induces host factor nucleolin to support its latency and life cycle and targeting nucleolin with AS1411 would have therapeutic potential in KSHV associated malignancies. To test this hypothesis, we have formulated two specific aims in which we will 1) To determine the regulatory mechanisms of nucleolin expression upon KSHV infection and its role in KSHV latency, and 2) To evaluate the chemotherapeutic potential of using AS1411 to treat KS and PEL. Our studies are significant and will have a positive impact by advancing the unexplored and novel targeted theranostic field of aptamers in KSHV biology and understanding their antiviral and anticancer potential can also be applied to other viral malignancies.