Abstract LB-435: Regulation of emmprin in Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells: a novel strategy developed against KSHV-related diseases

Abstract

Abstract Purpose: KSHV is a common etiologic agent for cancers arising in the setting of immune suppression, including Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). We recently reported that the KSHV-encoded latency-associated nuclear antigen (LANA) upregulates expression of the multifunctional membrane glycoprotein emmprin (Extracellular Matrix MetalloPRoteinase Inducer) and associated cell invasiveness and colony formation (Qin et al. Cancer Res. 2010; 70(10): 3884–9). The purpose of this study was to determine mechanisms for KSHV/LANA-induced transcriptional activation of emmprin, and whether these interactions affect emmprin-mediated signal transduction. Experimental Design: We used co-IP, confocal microscopy, gene silencing, and overexpression of LANA deletion mutants to whether specific transcription factors (TF) interact with LANA and mediate LANA-initiated emmprin activation, as well as putative sites of LANA-TF interactions. Pharmacological inhibitors, gene transfer, immunoblots, qRT-PCR, ELISA and transwell assays were performed to assess how LANA-TF interactions impact emmprin-dependent intracellular signal transduction and downstream pathogenesis. Results: We found that Sp1, a Zn finger TF, mediates LANA activation of emmprin transcription/protein expression and cell invasiveness. The N-terminal domain of LANA, containing a nuclear localization sequence, is necessary and sufficient for Sp1 activation of emmprin and co-localizes with Sp1 in the nucleus. Interestingly, we also found that emmprin-dependent activation of pro-migratory cytokines/chemokines and endothelial cell invasiveness following de novo KSHV infection is dependent upon KSHV induction of PI3K/Akt and ERK signaling, but not NF-κB pathway. Conclusions: LANA interactions with Sp1, and KSHV induction of Akt- and MAPK-dependent signaling, initiate transcriptional activation of emmprin and emmprin-dependent activation of pro-migratory cytokines release and cell invasiveness following KSHV infection. Ongoing experiments to clarify regulatory networks for emmprin activation in KSHV-infected cells may lead to identification of novel therapeutic targets for KSHV-related diseases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-435. doi:10.1158/1538-7445.AM2011-LB-435