Inhibitors of apoptosis confer resistance to tumour suppression by adoptively transplanted cytotoxic T-lymphocytes in vitro and in vivo

Deregulation of apoptosis signalling is commonly found in cancer and results in resistance to cytotoxic therapies. Immunotherapy is a promising strategy to eliminate resistant cancer cells. The transfer of T-lymphocytes during allogeneic stem cell transplantation is clinically explored to induce a 'graft-versus-tumor' effect (GvT). Cytotoxic T-lymphocytes (CTL), which are major effectors of GvT, eliminate cancer cells by inducing apoptosis via multiple parallel pathways. Here, we study in vitro and in vivo the susceptibility of murine cancer cells engineered to express single antiapoptotic genes to CTL-mediated cytotoxicity. Interestingly, we find that single inhibitors of caspase activatio…

Gen-Immuntherapie zur Gen-Immuntherapie zur Behandlung von Malignomen Behandlung von Malignomen

Entartete Zellen unterliegen, so eine derzeitige Hypothese, der auseren Kontrolle durch das Immunsystem. Dies ist in der Lage, von Tumorzellen prozessierte und uber Haupthistokompatibilitatskomplexe (MHC) prasentierte Peptide via T-Zellen zu erkennen. Da Tumorzellen sich bei der Prasentation von Peptiden in den MHC-Komplexen durch Peptid-Quantitat und/oder Peptid-Qualitat (so genannte Tumorantigene) von den normalen Zellen unterscheiden, kann dies zu ihrer Erkennung und Zerstorung fuhren. Kommt es zur Manifestation eines Malignoms, so hat offensichtlich diese immunologische Kontrolle versagt. Die Grunde hierfur sind vielfaltig: Verlust der Fahigkeit zur Prasentation von Tumorantigenen, redu…

Blockade of PD-L1 (B7-H1) augments human tumor-specific T cell responsesin vitro

Human tumors frequently escape immune destruction, despite the presence of cytotoxic T cells (CTL) recognizing tumor-associated antigens (TAA). We have previously shown that programmed death ligand-1 (PD-L1), a recently identified ligand of the B7 superfamily, is expressed on murine tumors and can inhibit antitumor immune responses. To evaluate the clinical relevance of our animal model findings, we examined human tumors and tumor-specific T cells. We found PD-L1 to be constitutively expressed on human renal cell carcinoma (RCC) cell lines and upregulated on human melanoma cell lines upon exposure to interferon-gamma. Similarly, we found binding of anti-PD-L1 monoclonal antibody (mAb) on fr…

Vaccination with WT1 and PR3 Derived Peptides in Patients with AML/MDS and MUC1 Peptides in Patients with Multiple Myeloma - Preliminary Results.

Abstract Background: It has been demonstrated that the Wilms Tumor gene (WT1) is highly expressed in various types of leukaemia. WT1 expression level reflects the extent of minimal residual disease and significantly increases at relapse. Proteinase 3 (Pr3) is an aberrantly expressed myeloid leukaemia protein and T cells with specificity for both, Wt1 and Pr3 derived antigens, have been generated in vitro from healthy individuals and cancer patients and lysed myeloid leukaemic blasts. MUC1(CD227) is presented on a considerable amount of multiple myeloma cell lines and plasmocytoma cells. MUC1-derived HLA-class I/II epitopes represent universal tumor antigens, which are also expressed by mali…

Playing the Game Together: Coexpression of a Single Chain T Cell Receptor and a T Cell Receptor Constant-Alpha Domain Triggers Tumor Reactivity.

Abstract Grafting T cells by tumor-antigen specific T cell receptors (TCR) could trigger the initiation of effector function and redirect T cell cytotoxicity towards tumors. We utilized various HLA-A2.1 transgenic mice to bypass human MDM2- and p53-specific self-tolerance. In contrast to the use of HuCD8×A2Kb transgenic mice to generate an MDM2-specific CD8-dependent TCR, we generated a high-affinity, CD8-independent p53-specific TCR in single human A2.1 transgenic mice. The efficiency of double chain (dc) TCR modified T cells could be affected by the incorrect TCR α/β chain pairing between endogenous and transgenic TCR constructs to form hybrid TCR potentially leading to autoimmunity. To a…

Targeting Acute Leukemia and Cancer by High-Affinity T-Cell-Receptor Transfer

Accumulation and subsequent overexpression of human mdm2 (hdm2) and altered p53 protein is associated with high-level presentation of hdm2 and wild-type (wt) p53 derived peptides by major histocompatibility complex (MHC) class I molecules on a wide range of malignant cells. A major barrier to the design of broad-spectrum hdm2 and p53 specific immunotherapeutics for leukemia and cancer, however, has been the observation that low-level expression of hdm2 and wt p53 peptides by non-transformed tissues and cells results in self-tolerance of T-lymphocytes with high avidity for self-class I MHC / self-peptide complexes. Although the peripheral T-cell repertoire is mostly devoid of such high-avidi…

Generating p53-specific cytotoxic T lymphocytes by recombinant adenoviral vector-based vaccination in mice, but not man.

Mutations and aberrant expression of the p53 tumor suppressor protein are the most frequent molecular alterations in human malignancy. Peptides derived from the wild-type (wt) p53 protein and presented by major histocompatibility complex (MHC) molecules for T lymphocyte recognition are believed to serve as universal tumor-associated antigens for cancer immunotherapy. We studied the immunogeneicity of a recombinant replication-defective adenoviral vector encoding human full-length wt p53 (rAd/hup53) in human leukocyte antigen (HLA)-A2K(b)-transgenic (Tg) mice and man. The generation of p53 epitope-specific cytotoxic T lymphocytes (CTLs) in p53-proficient and p53-deficient A2K(b)-Tg mice was …

The Programmed Death (PD)‐1/PD‐Ligand 1 Pathway Regulates Graft‐Versus‐Host‐Reactive CD8 T Cells After Liver Transplantation

Acute graft-versus-host disease (aGVHD) is a life-threatening complication after solid-organ transplantation, which is mediated by host-reactive donor T cells emigrating from the allograft. We report on two liver transplant recipients who developed an almost complete donor chimerism in peripheral blood and bone marrow-infiltrating T cells during aGVHD. By analyzing these T cells directly ex vivo, we found that they died by apoptosis over time without evidence of rejection by host T cells. The host-versus-donor reactivity was selectively impaired, as anti-third-party and antiviral T cells were still detectable in the host repertoire. These findings support the acquired donor-specific allotol…

Gentherapeutischer T-Zell-Rezeptor-Transfer