A Novel Treatment for Ocular Tumors that Terminates Immune Privilege and Activates Innate Immunity

Abstract

Abstract: : Purpose:Ocular immune privilege promotes tumor growth by hindering the development of innate and adaptive immunity. Previously, we demonstrated that ocular tumors expressing the membrane-only form of Fas Ligand (FasL) (i) terminate immune privilege, (ii) induce vigorous inflammation, (iii) are rejected, and (iv) induce systemic protective immunity. These experiments utilized tumor cells that were genetically engineered to express membrane FasL. In order to translate this research into a clinical treatment, the present study examined whether injection of microvesicles expressing membrane FasL into FasL negative ocular tumors would have a similar effect.Methods and Results:Microvesicles expressing either no FasL, or membrane-only Fas Ligand were co-injected with L5178Y-R lymphoma cells into the anterior chamber of DBA/2 mouse eyes. Microvesicles were prepared from Neuro-2A cells transfected with either murine membrane FasL, or a control vector. Western blot analysis of the microvesicles revealed a high level of membrane FasL protein. The membrane FasL on microvesicles was functional and triggered apoptosis in Fas receptor positive target cells. Tumor cells injected alone or in conjunction with control vesicles grew progressively in the anterior chamber and 100% of the mice succumbed to metastatic disease by day 13. By contrast, co-injection of tumor cells with membrane-Fas Ligand microvesicles induced a potent inflammatory response, resulting in a significant delay in tumor growth and metastatic disease in all mice. Tumor rejection resulting in phthisis occurred in 30% of the mice.Conclusions:Bioactive membrane FasL microvesicles co-injected with tumor cells induce a potent inflammatory response that terminates immune privilege, eliminates ocular tumors, and prevents metastatic disease.

Keywords: anterior chamber • tumors • inflammation