Presentation Abstract

Abstract Number: 630
Presentation Title: Induction of anti-melanoma immunity after intralesional ablative therapy
Presentation Time: Sunday, Apr 06, 2014, 1:00 PM - 5:00 PM
Location: Hall A-E, Poster Section 27
Poster Board Number: 5
Author Block: Hao Liu, Krithika Kodumudi, Amy Weber, Amod A. Sarnaik, Shari Pilon-Thomas. Moffitt Cancer Center, Tampa, FL
Abstract Body: Immunotherapeutic strategies incorporating intralesional (IL) ablative therapy to elicit a tumor specific immune response are under investigation as a non-surgical option to induce tumor regression of cutaneous neoplasms. Rose Bengal (RB) is a water-soluble xanthene dye that was originally used as an intravenous liver diagnostic and is in use by ophthalmologists to stain damaged cells in the eye. In murine models of breast cancer and melanoma, we have shown that IL injection of PV-10 (10% RB in saline solution) leads to ablation of injected tumors and regression of non-injected bystander tumors. In these models, increased anti-tumor T cell responses were measured, supporting the induction of systemic anti-tumor immunity after tumor ablation with PV-10. In our ongoing phase I clinical trial exploring melanoma regression in patients, IL PV-10 has led to a significant decrease of melA positive melanoma cells in the biopsies of both PV10-injected and non-injected lesions. This regression correlated with increased circulating CD3+T cells (p=0.03) in peripheral blood mononuclear cells (PBMC). T cells purified from PBMC from a melanoma patient produced increased IFN-gamma in response to autologous tumor after treatment with PV-10. Ex vivo models implemented to investigate this phenomenon indicate that the cytotoxicity induced by PV-10 is not apoptosis-dependent as evidenced by Annexin staining of melanoma cells following PV-10 treatment. PV-10 directly induced necrosis of melanoma cells at 50 uM, but was not toxic to healthy fibroblasts at the same dose. Further preclinical translational testing has shown that treatment of murine B16 cells with PV-10 leads to release of HMGB1, a soluble Damage Associated Molecule Pattern (DAMP) that is important for activation of dendritic cells (DCs). In the murine B16 melanoma model, there is a significant increase in the number of DCs infiltrating the tumor-draining lymph nodes after IL injection of PV-10. These findings suggest that PV-10 treatment leads to the release of DC activating factors and DC recruitment. Further studies to determine the role of PV-10 on T cell activation are ongoing. In sum, these clinical and preclinical results increase our understanding of the cytotoxic and immunological mechanisms that may play a role in systemic immunity induced by PV-10 tumor ablation.