Redirection of primary T lymphocytes towards HER2 by T cell receptor gene transfer

Abstract

3061 Background: The human epidermal growth factor receptor 2 (HER2) has been targeted as a breast cancer-associated antigen by T cell-based immunotherapeutical strategies. Until now several vaccination studies against HER2 which is overexpressed in about 25% of breast cancer were performed but the objective response rate achieved was only low. The goal of our studies is the adoptive transfer of primary T cells transduced with a HER2-specific T cell receptor (TCR) for patients with HER2-overexpressing breast cancer. Methods: CD8+ T cells isolated from an HLA-A2- donor were stimulated with allogeneic HLA-A2+ dendritic cells (DC) pulsed with the peptide HER2369–377 known to be naturally presented with HLA-A2. HER2369–377 specific T cells were screened via ELISpot and FACS sorting, respectively, cloned and further tested in 51Chromium release assays (51CRA) and ELISA using the corresponding HER3 and HER4 peptides pulsed on as well as HER2-, HER3- and HER4 overexpressing cell lines. Retroviral vectors containing the TCRα or β chain of a HER2-, HER3- and HER4 reactive cytotoxic T cell (CTL) clone were constructed. Following virus production in HEK293 T cells CD8+ T cells were transduced with the retrovirus and tested in IFN-γ ELISA and 51CRA. Results: The CD8+ T cells transduced with the HER2-specific TCR recognized the same panel of HLA-A2-matched, HER2-overexpressing cell lines as the parental CTL clone. As the parental CTL clone, the TCR- transduced T cells were not only able to recognize HER2369–377 but also the corresponding peptides from HER3 and HER4 as determined by lytic activity and cytokine secretion. Conclusions: The fine specificity of a HER2-reactive TCR which also cross-reacts with the corresponding peptides from HER3 and HER4 is conserved following its transduction into CD8+ T cells. This is a promising result for the HER2-directed design of immunotherapies based on TCR-transduced T cells. Cross-recognition especially of HER3 may be beneficial as HER2 and HER3 overexpressing tumors are particularly aggressive. No significant financial relationships to disclose.