Presentation of native TROP-2 tumor antigens to human cytotoxic T lymphocytes by engineered antigen-presenting cells.

Professional antigen-presenting cells (APC), e.g. dendritic cells, express immuno-proteasome components and process proteins for MHC presentation differently from non-immune cells. Thus, they induce reactivities against sets of peptides that do not overlap with those generated by non-professional APC, i.e., tumor cells, and stimulate cytotoxic T lymphocytes (CTL) that may not recognize them. The goal of this work was to establish a system for antigen presentation and in vitro stimulation of human CTL using "tumor-cell-like" engineered APC. Murine fibroblasts were transfected with human HLA Class I alleles, together with the B7.1, ICAM-1 and germ-line TROP2 genes. The last encodes a cell surface glycoprotein widely expressed by human cancers. Unseparated peripheral blood mononuclear cells from HLA Class I-matched individuals were stimulated in vitro by the engineered APC. These efficiently induced the activation and proliferation of antigen-specific HLA-restricted CTL lines and clones. The Trop-2-specific CTL demonstrated high specific cytotoxicity against the appropriate transfected target cells. They also efficiently lysed MCF-7 human tumor cells expressing endogenous HLA-A2.1, Trop-2 together with ICAM-1. These results demonstrate that Trop-2 is a target molecule recognized by human CTL. Moreover, they demonstrate that non-immune engineered APC efficiently process and present native tumor-specific proteins in the context of human MHC Class I, and stimulate the growth and cytotoxicity of specific anti-tumor CTL. Copyright 2002 Wiley-Liss, Inc.