Abstract 2292: Reconstitution of myeloid derived suppressor cells after the induction of lymphopenia and TIL therapy

Abstract

Abstract Factors such as T regulatory (Treg) cells and myeloid derived suppressor cells (MDSC) limit the effectiveness of current immunotherapy protocols. Several reports have shown that administration of chemotherapeutic agents or total body irradiation (TBI) before adoptive transfer of tumor-specific T cells reduces or eliminates the immunosuppressive populations such as Tregs and MDSC. A previous study in our lab has shown that MDSC that reconstitute after lymphodepletion are highly suppressive compared to the endogenous MDSC in a B16 melanoma model. Blockade of MDSC expansion in combination with adoptive T cell transfer delayed tumor growth and improved survival rate. However, there is very little known about the MDSC reconstitution after the adoptive transfer of tumor infiltrating lymphocytes (TIL) in melanoma patients. Melanoma patients were treated with non- myeloablative therapy that included cyclophosphamide and fludarabine. At the time of TIL transfer, no circulating lymphoid or myeloid cells were detected in the PBMC. One day after completion of chemotherapy, up to 100 billion TIL were transferred followed by high dose bolus IL-2. At weeks 1-4 after TIL transfer, PBMC were collected and we investigated the reconstitution and the suppressive function of MDSC. MDSC were phenotyped by flow cytometry as HLA-DR− Lin− CD14+CD33+ or CD11b+CD14−CD33+. While 3-15% of MDSC was observed in the PBMC of melanoma patients as their baseline, after lymphodepletion and one week post TIL infusion, the percent of MDSC increased to 10-30% and gradually dropped to baseline by week 4. To examine suppressive function, MDSC were isolated from peripheral blood at 1-2 weeks after TIL infusion and co-cultured with healthy donor T cells or patient TIL. MDSC were highly suppressive and abrogated T cell proliferation and IFN-gamma secretion. Furthermore, in patients that responded to TIL therapy, the ratio of peripheral MDSC to total CD8+ T cells was lower. These studies demonstrate that MDSC that reconstitute post- lymphodepletion are suppressive and may potentially interfere with robust T cell function. Further studies are warranted to clarify the role of MDSC in the efficacy of TIL therapy. Blocking MDSC in combination with TIL therapies represent an improved strategy for the treatment of melanoma patients. Citation Format: Krithika N. Kodumudi, Doris Wiener, Amy Weber, Erica Royster, Linda Kelley, Amod Sarnaik, Shari Pilon-Thomas. Reconstitution of myeloid derived suppressor cells after the induction of lymphopenia and TIL therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2292.