Immune-Based Therapies Targeting Mage-A4 for Relapsed/Refractory Hodgkin's Lymphoma After Stem Cell Transplant.

Abstract 4089

Poster Board III-1024

Stem cell transplantation (SCT) from autologous and, recently, allogeneic (unrelated adult donor and umbilical cord blood) sources is the treatment of choice for patients with relapsed/refractory Hodgkin's Lymphoma (HL). However, HL patients who relapse after SCT have limited options for long-term cure – necessitating the development of novel therapies for the treatment of this disease. We have previously shown that infusion of cytotoxic T cells (CTLs) targeting Epstein Barr virus (EBV)-derived proteins induced complete remissions in EBV+ HL patients. Unfortunately, approximately 70% of relapsed HL tumors are EBV-negative. Therefore, we investigated another promising T cell target, the cancer/testis antigen (CTA) MAGE-A4 as a potential target for CTL therapy. We hypothesize that adoptive transfer of MAGE-A4-specific T cells may be a feasible therapeutic strategy for patients with relapsed HL after SCT. MAGE-A4 is expressed by >30% of EBV antigen-negative HL tumors and expression can be enhanced in MAGE-A4-negative tumors by epigenetic modification using HDAC inhibitors/demethylating agents that are currently in clinical use. We therefore determined whether MAGE-A4-specific cytotoxic T lymphocytes (CTL) could be expanded from healthy adult donor peripheral blood (PB) (n=9), cord blood (CB) (n=2) and HL patient blood (n=3). Dendritic cells (DCs) pulsed with overlapping peptides spanning MAGE-A4 were used as antigen presenting cells to stimulate peripheral blood mononuclear cells in the presence of IL-7, IL-12, and IL-15. After 9-12 days in culture, cells were stimulated weekly (with at least one additional stimulation) with MAGE-A4 peptide-pulsed DCs in the presence of IL7 and IL2. Analysis of the stimulated T cells using interferon gamma (IFN-γ) ELISPOT assays showed high specificity against MAGE-A4 with mean 96.6 (range 11-716) IFNγ-secreting spot forming cells (SFC)/10e5 cells in response to MAGE-A4 peptides compared to a mean of 7.8 (range 0-46.5) SFC/10e5 cells in response to irrelevant peptides. In addition, specific killing was measured in chromium (Cr51) release assays following co-culture with MAGE-A4 positive targets, showing that we successfully generated cytotoxic T cells. All evaluable T cell lines generated from healthy adult donors were predominantly CD8+, and 4 of the 8 showed specificity for a single, previously uncharacterized MAGE A4 epitope (aa266-285, NPARYEFLWGPRALAETSYV). In contrast, 6/8 T-cell lines derived from HL patients and CB were predominantly CD4+, and showed a range of MAGE-A4 epitope specificities. Mechanisms for these differences are now being investigated. These early results suggest that strategies using healthy donor cord blood and patient T cells for adoptive immunotherapy may be a novel and feasible approach for the treatment of relapsed HL post SCT.