No abstract

Adoptive transfer of T cell receptor (TCR)-transduced T cells may be an attractive strategy to target both hematological malignancies and solid tumors. By introducing a TCR, large numbers of T cells with defined antigen (Ag) specificity can be obtained. However, by introduction of a TCR, mixed TCR dimers can be formed. Besides the decrease in TCR expression of the introduced and endogenous TCR, these mixed TCR dimers could harbor potentially harmful specificities. In this study, we demonstrate that introduction of TCRs resulted in formation of neoreactive mixed TCR dimers, composed of the introduced TCR chains pairing with either the endogenous TCR α or β chain. Neoreactivities observed were HLA class I or class II restricted. Most neoreactive mixed TCR dimers were allo-HLA reactive; however, neoreactive mixed TCR dimers with autoreactive activity were also observed. We demonstrate that inclusion of an extra disulfide bond between the constant domains of the introduced TCR markedly reduced neoreactivity, whereas enhanced effectiveness of the introduced TCR was observed. In conclusion, TCR transfer results in the formation of neoreactive mixed TCR dimers with the potential to generate off-target effects, underlining the importance of searching for techniques to facilitate preferential pairing.

Purpose: In human leukocyte antigen (HLA)–matched stem cell transplantation (SCT), it has been shown that beneficial immune response mediating graft-versus-tumor (GVT) responses can be separated from graft-versus-host disease (GVHD) immune responses. In this study, we investigated whether it would be possible to dissect the beneficial immune response of allo-HLA–reactive T cells with potent antitumor reactivity from GVHD-inducing T cells present in the detrimental immune response after HLA-mismatched SCT. Experimental Design: The presence of specific tumor-reactive T cells in the allo-HLA repertoire was analyzed at the time of severe GVHD after HLA-mismatched SCT, using tetramers composed of different tumor-associated antigens (TAA). Results: High-avidity allo-HLA-restricted T cells specific for the TAA preferentially expressed antigen on melanomas (PRAME) were identified that exerted highly single-peptide–specific reactivity. The T cells recognized multiple different tumor cell lines and leukemic cells, whereas no reactivity against a large panel of nonmalignant cells was observed. These T cells, however, also exerted low reactivity against mature dendritic cells (DC) and kidney epithelial cells, which was shown to be because of low PRAME expression. Conclusions: On the basis of potential beneficial specificity and high reactivity, the T-cell receptors of these PRAME-specific T cells may be effective tools for adoptive T-cell therapy. Clinical studies have to determine the significance of the reactivity observed against mature DCs and kidney epithelial cells. Clin Cancer Res; 17(17); 5615–25. ©2011 AACR.

T cell factor (Tcf) proteins bind ␤-catenin and are downstream effectors of Wnt/␤-catenin signals. A recently demonstrated interaction between ␤-catenin and the androgen receptor (AR) ligand binding domain has suggested that AR may be a Tcf-independent Wnt/␤-catenin effector. This study demonstrates that there is a direct interaction between the AR DNA binding domain (DBD) and Tcf4. Tcf4 bound specifically to a glutathione S-transferase-ARDBD fusion protein and could be coimmunoprecipitated with ␤-catenin and transfected AR or endogenous AR in prostate cancer cells. Transfected Tcf4 repressed the transcriptional activity of full-length AR and a VP16-ARDBD fusion protein, and this repression was only partially reversed by transfected ␤-catenin. AR activation by cyproterone acetate, a partial agonist that did not support ␤-catenin binding to the AR, was also repressed by Tcf4, further indicating that repression was not due to ␤-catenin sequestration. Tcf4 could recruit ␤-catenin to the AR DBD in vitro and to the cyproterone acetate-liganded AR in vivo. Chromatin immunoprecipitation experiments in LNCaP prostate cancer cells showed that endogenous AR was bound to a Tcf4-responsive element in the c-myc promoter. These findings indicate that AR and Tcf4 can interact directly and that this interaction may occur on the promoters or enhancers of particular genes. The direct AR-Tcf4 interaction, in conjunction AR-and Tcf4-␤-catenin binding, provides a mechanism for cooperative and selective gene regulation by AR and the Wnt/␤-catenin-Tcf pathway that may contribute to normal and neoplastic prostate growth. The androgen receptor (AR)1 is a steroid hormone receptor member of the larger nuclear receptor superfamily and plays a central role in normal male development and prostate cancer (1, 2). It contains a highly conserved central DNA binding domain (DBD), a C-terminal ligand binding domain (LBD), and a large N-terminal transactivation domain. AR activation by androgen binding causes a conformational change that enhances nuclear localization, homodimerization, and binding to specific sequences (androgen-responsive elements, AREs) located in androgen-regulated genes. The androgen-induced conformational change in the AR LBD also generates a binding site for a short hydrophobic motif (Leu-X-X-Leu-Leu or LXXLL) found in many transcriptional coactivator proteins, although the AR N terminus contains an LXXLL-like sequence that binds strongly to the liganded LBD and may compete for binding with other LXXLL-containing coactivators (3). Similarly to other steroid hormone and nuclear receptors, protein-protein interactions involving one or more domains of the AR mediate the recruitment of multiple transcription factors, with subsequent chromatin remodeling and transcription of androgen regulated genes (4).The binding of AR and other steroid hormone receptors to DNA can be enhanced by HMG-1 and HMG-2, related nonsequence-specific DNA binding proteins characterized by a high mobility group (HMG) box DBD (5-10). HMG box-containing prot...