ARTICLE ABSTRACT
Purpose: Cultured tumor fragments from melanoma metastases have been used for years as a source of tumor-infiltrating lymphocytes (TIL) for adoptive cell therapy (ACT). The expansion of tumor-reactive CD8+ T cells with interleukin-2 (IL2) in these early cultures is critical in generating clinically active TIL infusion products, with a population of activated 4-1BB CD8+ T cells recently found to constitute the majority of tumor-specific T cells.Experimental Design: We used an agonistic anti–4-1BB antibody added during the initial tumor fragment cultures to provide in situ 4-1BB costimulation.Results: We found that addition of an agonistic anti–4-1BB antibody could activate 4-1BB signaling within early cultured tumor fragments and accelerated the rate of memory CD8+ TIL outgrowth that were highly enriched for melanoma antigen specificity. This was associated with NFκB activation and the induction of T-cell survival and memory genes, as well as enhanced IL2 responsiveness, in the CD8+ T cells in the fragments and emerging from the fragments. Early provision of 4-1BB costimulation also affected the dendritic cells (DC) by activating NFκB in DC and promoting their maturation inside the tumor fragments. Blocking HLA class I prevented the enhanced outgrowth of CD8+ T cells with anti–4-1BB, suggesting that an ongoing HLA class I–mediated antigen presentation in early tumor fragment cultures plays a role in mediating tumor-specific CD8+ TIL outgrowth.Conclusions: Our results highlight a previously unrecognized concept in TIL ACT that the tumor microenvironment can be dynamically regulated in the initial tumor fragment cultures to regulate the types of T cells expanded and their functional characteristics. Clin Cancer Res; 21(3); 611–21. ©2014 AACR.
