EXTH-27. TRANSLATABLE CCL3 THERAPY TO PROMOTE DC VACCINE MIGRATION AND EFFICACY AGAINST GLIOMA

Abstract

Abstract INTRODUCTION Prior evidence from our studies have identified chemokine ligand 3 (CCL3) as a key modulator to increase DC vaccine migration to vaccine draining lymph nodes (VDLNs) which is associated with improved long-term survival clinically. METHODS The effect of CCL3 treatment on DC vaccine migration ex vivo and in vivo (n=5), antigen-specific T cell responses (n=5), and efficacy against orthotopic GL261-OVA and SMA560 tumors (n=10) was studied in C57Bl/6 and VMdK mice. CCL3 treatment of mouse and human DC vaccines ex vivo was also tested in transwell assays. DCs were electroporated with OVA-mRNA or pulsed with ODC1 neoantigen peptide. DC migration and T cell responses were quantified by flow cytometry. Median overall survival (mOS) was measure in days (d) post-intracranial implantation. RESULTS Ex-vivo treatment of DC vaccines with 20ng/mL CCL3 (18 and 1hr pre-injection) increased transwell (mouse and human) migration and to VDLN. In vivo systemic CCL3 treatment also resulted in a dose-dependent increase in migration of DC vaccine to VDLN (10µg, 20µg, 50µg). CCL3 added to DC vaccination generated more tumor antigen-specific CD8+IFNγ+ T cells at 7-days. CCL3 with tumor antigen-DC treatment also resulted in significantly greater survival compared to OVA-DC alone (GL261-OVA: mOS DCvac: 19.5d, CCL3+DCvac 37d, p=0.0174; SMA560: mOS: DCvac: 25d, CCL3+DCvac: 48d, p=0.002). CONCLUSIONS These data combined with previous success of our DC vaccine clinical trials reflect the potency of CCL3 to enhance DC vaccine-specific migration, immune responses, and survival. CCL3 is a novel and safe adjuvant to overcome prior limitations in DC vaccine therapy and may be translatable to increase heterogeneous tumor antigen presentation following vaccine-targeted tumor killing. CCL3 used as a drug could increase vaccine migration without potential systemic toxicity in patients with glioblastoma.