Abstract 3035: Targeting of PDGFRβ with a novel RNA-aptamer inhibits glioma cell survival, growth, invasion and enhances antitumor activity of an anti-EGFR aptamer.
Authors: Camorani Simona , Esposito Carla Lucia , Catuogno Silvia , Rienzo Anna , Iaboni Margherita , Condorelli Gerolama , de Franciscis Vittorio , Cerchia Laura 
Published: August 2014

The platelet-derived growth factor receptor (PDGFR) is an important member of receptor tyrosine kinase (RTK) family. The activation of PDGFRβ signaling pathway induces various cellular responses, including cell proliferation, migration and angiogenesis. Preclinical studies have not only shown a central role for the overexpression and deregulated activation of PDGFRβ-mediated signaling in development of many tumors, including glioma, and the maintenance of the malignant phenotype, but have also demonstrated that the targeted inhibition of signaling cascades has significant anti-cancer effects. Also, several studies have reported that epidermal growth factor receptor (EGFR) cross-talk with PDGFRβ potentially leads to malignant glioblastoma resistance to anti-EGFR therapy and that EGFR transactivation contributes importantly to PDGFRß signal transduction. Overall these data indicate that PDGFRβ represents a valuable target for tumor therapeutic development. A number of tyrosine kinase inhibitors under development as anti-tumor agents have been found to inhibit the PDGFRβ. However, these compounds are not selective and have multiple tyrosine kinase targets. Aptamers are single-stranded oligonucleotides able to bind at high affinity to specific protein by folding into complex tertiary structures. Their high specificity and low toxicity render them a valid alternative to antibodies for in vivo targeted recognition as therapeutics or delivery agents for nanoparticles, small interfering RNAs, chemotherapeutics and molecular imaging probes. Here we report a novel PDGFRß-specific antagonist that is a nuclease resistant RNA-aptamer, named Gint4. The aptamer, generated by cell-SELEX on glioma U87MG cells, specifically binds to the extracellular domain of the human PDGFRß (Kd, 10.4 nM). Following binding, the aptamer inhibits ligand-dependent receptor activation, including Erk and Akt phosphorylation, cell growth, migration and invasion. Further, we demonstrated that stimulation of glioma cells with the PDGFRß specific ligand, PDGF-BB, caused EGFR transactivation that was hampered by treatment with both the Gint4 aptamer as well as with CL4, the RNA aptamer that we have previously generated as an high affinity inhibitor of EGFR. Interestingly, the combined treatment of glioma cells with the anti-PDGFRß Gint.4 aptamer together with the anti-EGFR CL4 aptamer strongly cooperates in inducing inhibition of cell survival and growth. Moreover, we demonstrated that Gint4 rapidly and specifically internalizes within the target cells thus it can be used as cargo for tissue specific internalization.

Citation Format: Simona Camorani, Carla Lucia Esposito, Silvia Catuogno, Anna Rienzo, Margherita Iaboni, Gerolama Condorelli, Vittorio de Franciscis, Laura Cerchia. Targeting of PDGFRβ with a novel RNA-aptamer inhibits glioma cell survival, growth, invasion and enhances antitumor activity of an anti-EGFR aptamer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3035. doi:10.1158/1538-7445.AM2013-3035