Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Hasahn Conway - Xavier University of LA
Co-Author(s): Tajhshea Walden, Magdalena Angelova, and Moamen Ismail, Aizaz Ahmad, and Harris McFerrin, Xavier University of Louisiana, New Orleans Kenneth Swan, MaryBeth Ferris, Cindy Morris, and Deborah Sullivan, Tulane University, Louisiana, New Orleans
Kaposi’s sarcoma-associated herpesvirus (KSHV/HHV8) has been identified as the etiologic agent of Kaposi’s sarcoma (KS). In its most aggressive form, KS is a multifocal highly vascularized neoplasm that is the most common malignancy associated with acquired immunodeficiency syndrome (AIDS). Although highly active anti-retroviral therapy has decreased the incidence of KS, it remains an incurable tumor for which there is no established treatment. Due to the vascular nature of KS, an anti-angiogenic therapeutic approach is attractive. Recent evidence suggests that inhibition of P-TEFb, a transcriptional elongation factor composed of cyclin dependent kinase 9 (CDK9) and its regulatory partner cyclin T, is anti-angiogenic. The KSHV-encoded G-protein-coupled receptor (vGPCR) is required for and sufficient to initiate angiogenesis and tumorigenesis. Expression of vGPCR in endothelial cells has been shown to induce the secretion of an array of growth factors and cytokines including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), both potent pro-angiogenic factors that enhance endothelial cell survival. We have also shown that expression of vGPCR in endothelial cells upregulates expression of the anti-apoptotic gene Bcl-2 and enhances their survival upon serum starvation. Based on these data, we hypothesized that flavopiridol, a specific inhibitor of CDK9, would inhibit vGPCR-induced angiogenesis by downregulating expression of angiogenic growth factors and/or Bcl-2. Using primary human umbilical vein endothelial cells (HUVEC) transduced with either a control or a vGPCR-expressing retroviral vector, we demonstrate that CDK9 is directly activated upon vGPCR expression. vGPCR-expressing HUVECs also show significantly enhanced ability to form capillary-like tubules on growth factor-reduced Matrigel as well as enhanced migration towards chemotactic stimuli. Treatment with 50nM flavopiridol prior to and during the migration and tubule formation assays inhibited the vGPCR-enhanced formation of tubules and reduced their migration ability. These results correlated with a significant decrease in expression of VEGF-A, VEGF-C and Bcl-2 mRNA. Together these results suggest that P-TEFb plays a role in mediating transcriptional regulation of vGPCR responsive genes and implicate CDK9 as a potential target to reduce vGPCR-enhanced endothelial cell survival, angiogenesis and tumorigenesis.
Funder Acknowledgement(s): NIH NIGMS 8P20GM03424; NIH NIGMS 5RL5GM118966-03; NIH NIGMS student TL4GM118968; NIH NIGMS UL1GM118967; Louisiana Cancer Research Consortium
Faculty Advisor: Harris McFerrin, email@example.com
Role: I participated in plating of cells, infecting cells, and analyzing data.