The human epidermal growth factor receptor 2 (HER2) has been targeted as a breast cancer-associated antigen by immunotherapeutical approaches based on HER2-directed monoclonal antibodies and cancer vaccines. We describe the adoptive transfer of autologous HER2-specific T-lymphocyte clones to a patient with metastatic HER2-overexpressing breast cancer. The HLA/multimer-based monitoring of the transferred T lymphocytes revealed that the T cells rapidly disappeared from the peripheral blood. The imaging studies indicated that the T cells accumulated in the bone marrow (BM) and migrated to the liver, but were unable to penetrate into the solid metastases. The disseminated tumor cells in the BM disappeared after the completion of adoptive T-cell therapy. This study suggests the therapeutic potential for HER2-specific T cells for eliminating disseminated HER2-positive tumor cells and proposes the combination of T cell-based therapies with strategies targeting the tumor stroma to improve T-cell infiltration into solid tumors.

T cell receptor (TCR) gene transfer is a convenient method to produce antigen-specific T cells for adoptive therapy. However, the expression of two TCR in T cells could impair their function or cause unwanted effects by mixed TCR heterodimers. With five different TCR and four different T cells, either mouse or human, we show that some TCR are strong -in terms of cell surface expression -and replace weak TCR on the cell surface, resulting in exchange of antigen specificity. Two strong TCR are co-expressed. A mouse TCR replaces human TCR on human T cells. Even though it is still poorly understood why some TCRa/b combinations are preferentially expressed on T cells, our data suggest that, in the future, designer T cells with exclusive tumor reactivity can be generated by T cell engineering.

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The human epidermal growth factor receptor 2 (HER2) has been targeted as a breast cancer-associated Ag by T cell-based immunotherapeutical strategies such as cancer vaccines and adoptive T cell transfer. The prerequisite for a successful T cell-based therapy is the induction of T cells capable of recognizing the HER2-expressing tumor cells. In this study, we generated human cytotoxic T cell clones directed against the HER2369–377 epitope known to be naturally presented with HLA-A*0201. Those HER2-reactive CTLs, which were also tumor lytic, exhibited a similar lysis pattern dividing the targets in lysable and nonlysable tumor cells. Several HER2-expressing tumor cells became susceptible to CTL-mediated lysis after IFN-γ treatment and, in parallel, up-regulated molecules of the Ag-presenting machinery, indicating that the tumor itself also contributes to the success of CTL-mediated killing. Some of the HER2369–377-reactive T cells specifically cross-reacted with the corresponding peptides derived from the family members HER3 and/or HER4 due to a high sequence homology. The epitopes HER3356–364 and HER4361–369 were endogenously processed and contributed to the susceptibility of cell lysis by HER cross-reacting CTLs. The principle of “double” or “triple targeting” the HER Ags by cross-reacting T cells will impact the further development of T cell-based therapies.

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The gene transfer of alpha and beta chains derived from a defined TCR has been successfully applied to endow T cells with specificities directed against tumor-associated antigens. However, it is still unclear if the transfer of TCR genes into T cells that already express an endogenous TCRalpha and beta chain leads to engineered T cells expressing four different TCR complexes on their cell surface. Mixed TCR heterodimers composed of endogenous and exogenous TCR chains may acquire new specificities, which may cause unwanted reactions in patients following adoptive T cell transfer. We examined the possibility of mixed TCR heterodimer formation using defined conditions of single TCR chain transfer into human cytotoxic T cell (CTL) clones specific for CMV and Melan-A, respectively. After stimulation for three days CTLs were retrovirally transduced with the beta chain derived from a gp100-specific TCR. The expression of the exogenous (transduced) and the endogenous beta chain was distinguished by flow cytometry using antibodies against the different Vbeta motives. Indeed, CTLs that had been transduced with the single beta chain expressed this chain on the cell surface indicating the formation of mixed TCRs, because the expression of the exogenous TCRbeta chain requires the pairing with the endogenous TCRalpha chain. Furthermore, we transduced the CTL clones with both the TCRalpha and beta chain derived from a gp100-specific TCR. The transduced T cells were positively stained with an A2/gp100 multimer documenting the correct formation of the exogenous TCR chains. Functionality of transduced CTL clones was tested by antigen-specific IFN-gamma release and cytolytic activity. The TCR-transduced T cells were sorted with the A2/gp100 multimer and expanded for two weeks. Double staining with HLA multimers for the endogenous and the transduced TCRs showed the downregulation of the endogenous TCRs in three different CTL clones. In one CTL clone, the endogenous TCR was even replaced by the exogenous TCR as documented by flowcytometry and antigen-specific T cell function. In conclusion, transfer of single TCR chains in CTL clones can result in the formation of TCR heterodimers. However, our results also show that complete TCRs are predominantly expressed or can even replace other TCRs following transfer. The development of dominant TCRs will facilitate the therapeutical approaches of adoptive transfer regimens based on TCR-transduced T cells, because dominant TCRs can be selected or TCRs can be modified to be more dominant.

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Cancer testis (CT)-antigens belong to a class of tumor antigens that are aberrantly expressed in a variety of hematological malignancies including multiple myeloma. Owing to their restricted gene expression, CT-antigens represent potential target antigens for immunotherapeutical approaches such as vaccination and adoptive T cell transfer. As the CT-antigens are self antigens, the majority of CT-antigen-specific autologous T cells display a low avidity T cell receptor (TCR), which often results in a weak tumor recognition efficiency. Our group has been focusing on the isolation of highly avid T cells against CT-antigens that are expressed in multiple myeloma, in particular MAGE-C1, MAGE-C2, and NY-ESO-1. The experimental approach was based on the stimulation of allo-restricted cytotoxic T cells, because highly avid T cells recognizing peptide epitopes in context with foreign HLA-alleles are not depleted in the thymus. HLA-A2-negative T cells were stimulated with HLA-A2-positive allogeneic dendritic cells that had been exogenously loaded with HLA-A2-binding peptides derived from NY-ESO-1, MAGE-C1 or MAGE-C2. Using this technique we were able to isolate allo-HLA-A2-restricted cytotoxic T lymphocyte (CTL) clones with peptide-dominant binding against known and novel peptide epitopes derived from NY-ESO-1, MAGE-C1 and MAGE-C2. The expanded peptide-specific CTL clones lysed HLA-A2-positive myeloma cell lines expressing NY-ESO-1, MAGE-C1 and MAGE-C2, respectively. Of note, the MAGE-C1-specific T cells crossreacted with the corresponding MAGE-C2 peptide due to the existing sequence homology between MAGE-C1 and MAGE-C2. Current experiments focus on redirecting primary T cells toward myeloma cells by retroviral gene transfer of CT-antigen-specific TCRs. The establishment of a set of high avidity TCRs specific for CT-antigens facilitates the development of adoptive transfer regimens based on TCR-transduced T cells for the treatment of multiple myeloma.