Biomedical subjects

Thomas Blankenstein

Publications and source records attributed to Thomas Blankenstein.

31 records · Page 2Linked to original sources

PubMed2004

The role of inflammation in tumour growth and tumour suppression.

The relationship between inflammation and tumour growth is poorly understood. The quality, quantity and time point of the inflammatory response may decide whether inflammation supports or inhibits tumour growth. Three examples are given that illustrate the different role of inflammation for tumour growth. It will be shown that tumour infiltrating macrophages can contribute to tumour rejection, can be essential for tumour growth or can occur as innocent bystander cells in tumours. Then it will be shown that the timely arrival of T cells at the tumour site is critical for tumour rejection and that non-bone marrow-derived tumour stromal cells are important targets during tumour rejection. Finally, a protective inflammatory response against the chemical carcinogen methylcholanthrene (MCA) will be discussed. This response is related to a tissue repair response induced by the tissue damaging effects of the carcinogen in the course of which MCA is encapsulated and no longer able to induce tumours.

Animals↗

PubMed2003

Tumor rejection by modulation of tumor stromal fibroblasts.

Interleukin (IL)-4-secreting tumors are rejected in mice, an effect that is thought to be immune mediated. However, solid tumors are embedded in a stroma that often contains tumor-promoting fibroblasts, a cell population whose function is also affected by IL-4. Here we show that IL-4-secreting tumors grew undiminished in IL-4 receptor (R)-deficient (IL-4R-/-) mice. In IL-4R+/+ mice they were long-term suppressed in the absence of T cells but complete rejection required T cells, compatible with the assumption that hematopoietic cells needed to respond to IL-4. Surprisingly, bone marrow (BM) chimeric mice revealed that IL-4R expression exclusively on non-BM-derived cells was sufficient for tumor rejection. Fibroblasts in the tumor stroma were identified as a target cell type for IL-4 because they accumulated in IL-4-secreting tumors and displayed an activated phenotype. Additionally, coinjection of IL-4R+/+ but not IL-4R-/- fibroblasts was sufficient for the rejection of IL-4-secreting tumors in IL-4R-/- mice. Our data demonstrate a novel mechanism by which IL-4 contributes to tumor rejection and show that the targeted modulation of tumor-associated fibroblasts can be sufficient for tumor rejection.

Animals↗

PubMed2003

Transduction efficiency of MLV but not of HIV-1 vectors is pseudotype dependent on human primary T lymphocytes.

The success of several gene therapeutic approaches requires efficient transduction of human primary T lymphocytes. For this it is important to enhance the transduction efficiency, and this can be achieved by various means, mainly technical development of transduction procedures and use of different vectors and vector pseudotypes. We analyzed the transduction efficiency of an HIV-1 vector encoding enhanced green fluorescent protein (GFP) as a marker gene and pseudotyped with the envelopes of MLV-A, MLV-10A1, GaLV, RD114, and VSV for human primary T lymphocytes in comparison to an MLV vector pseudotyped with the same envelopes. Pseudotyping of the MLV vector with the envelopes of 10A1 and GaLV resulted in efficient transduction of preactivated human primary T lymphocytes (32.4% and 32.7% CD3+/GFP+ cells, respectively) while MLV-A (14.0%), RD114 (8.8%), and VSV (1.5%) envelopes were less efficient when using titrated vector stocks equilibrated to a multiplicity of infection of 1. In contrast, the HIV-1 vectors pseudotyped with these envelope proteins transduced preactivated T lymphocytes with similar efficiency (approx. 20% CD3+/GFP+ cells). Thereby, CD4+ and CD8+ T lymphocyte subpopulations were transduced at equivalent levels. The similar performance of the different HIV-1 vector pseudotypes may be due in part to the similar half-lives of the vector particles. Independently of the envelope used for pseudotyping neither the MLV nor the HIV-1 vectors yielded any significant transduction in nonactivated T lymphocytes (below 0.55% of GFP+ cells)

CD4-CD8 Ratio↗

PubMed2003

Retroviral vectors for high-level transgene expression in T lymphocytes.

Efficient expression of genes transferred by retroviral vectors is a prerequisite for gene therapy, especially when the biological effect depends on the amount of transgene product. High-level gene expression is desirable for several gene therapy approaches involving T lymphocytes. We evaluated standard retroviral vectors with cis-regulatory control elements of the Moloney murine leukemia virus (Mo-MLV) with or without the human T cell-specific CD2 enhancer. For comparison, vectors containing the long terminal repeat (LTR) of myeloproliferative sarcoma virus (MPSV) and an improved 5' untranslated region were used (MP71 vectors), with or without the woodchuck hepatitis virus posttranscriptional regulatory element (PRE). All vectors expressed the enhanced green fluorescent protein (GFP) to measure transgene expression. In mouse T cells MP71 vectors with and without the PRE yielded an up to 10-fold higher expression level compared with the Mo-MLV-based vectors currently used for gene transfer into T lymphocytes. A high multiplicity of infection (MOI) of standard Mo-MLV vectors could not reach expression levels obtained with a low MOI of MP71 vector. Ex vivo-transduced mouse T lymphocytes maintained the vector-dependent differences in level of transgene expression in Rag-1-deficient mice when adoptively transferred. In four human T cell lines and human primary T lymphocytes MP71 vectors yielded an up to 75-fold higher GFP expression level in comparison with the standard Mo-MLV vector. In contrast to mouse T cells, the integration of the PRE into MP71 vectors induced in human T cells a further significant increase in transgene expression level. Southern blot analysis of CEM T cells revealed that the superior performance of MP71 vectors was not due to a higher rate of viral integration. In summary, MP71 vectors are useful tools for stable, high-level gene expression in T lymphocytes, for example, in the expression of T cell receptor genes.

3T3 Cells↗

PubMed2003

A critical requirement of interferon gamma-mediated angiostasis for tumor rejection by CD8+ T cells.

It is thought that tumor rejection by CD8(+) T-cell effectors is primarily mediated by direct killing. We show that rejection of different tumors (fibrosarcoma, ras-transformed fibroblasts, colon carcinoma, and plasmacytoma) by CD8(+) T cells is always preceded by inhibition of tumor-induced angiogenesis. Angiostasis and tumor rejection were observed in perforin but not in IFN-gamma-deficient mice. Furthermore, adoptive transfer of tumor-specific CD8(+) T cells from IFN-gamma-competent mice inhibited angiogenesis of lung metastases in comparison to those from IFN-gamma gene-deficient mice. Taken together with our previous findings, we conclude that IFN-gamma-dependent antiangiogenesis is a general mechanism involved in tumor rejection by CD4(+) and CD8(+) T-cell effectors.

3T3 Cells↗

PubMed2003

Cutting edge: CD8+ effector T cells reject tumors by direct antigen recognition but indirect action on host cells.

CD8(+) effector T cells recognize malignant cells by monitoring their surface for the presence of tumor-derived peptides bound to MHC class I molecules. In addition, tumor-derived Ags can be cross-presented to CD8(+) effector T cells by APCs. IFN-gamma production by CD8(+) T cells is often critical for tumor rejection. However, it remained unclear whether 1) CD8(+) T cells secrete IFN-gamma in response to Ag recognition on tumor cells or APCs and 2) whether IFN-gamma mediates its antitumor effect by acting on host or tumor cells. We show in this study that CD8(+) effector T cells can reject tumors in bone marrow-chimeric mice incapable of cross-presenting Ag by bone marrow-derived APCs and that tumor rejection required host cells to express IFN-gammaR. Together, CD8(+) effector T cells recognize Ag directly on tumor cells, and this recognition is sufficient to reject tumors by IFN-gamma acting on host cells.

Animals↗

PubMed2003

Overexpression of NPM-ALK induces different types of malignant lymphomas in IL-9 transgenic mice.

Anaplastic large-cell lymphoma (ALCL) comprises approximately 25% of all non-Hodgkin lymphomas (NHL) in children and young adults, and up to 15% of high-grade NHL in older patients. Over 50% of these tumours carry the translocation t(2;5)(p23;q35). The result of this translocation is the fusion of the nucleophosmin (NPM) gene to the anaplastic lymphoma kinase (ALK) gene. The resulting hybrid protein contains the ALK catalytic domain that consequently confers transforming potential, which contributes to the pathogenesis of ALCL. To further analyse the transforming activity in an animal model, a cDNA encoding the protein product, NPM-ALK, was inserted into the retrovirus vector pLXSN and transduced into mouse bone marrow progenitors. These cells were subsequently used in a bone marrow transplant with the aim of reconstituting the haematopoietic compartments of lethally irradiated recipients. IL-9 transgenic mice were chosen as the animal model system, because dysregulated expression of the IL-9 gene in transgenic mice results in the sporadic development of spontaneous thymic lymphomas. Moreover, IL-9 is known to be expressed in cases of human ALCL. We used 15 IL-9 transgenic mice and eight corresponding wild-type mice (FVB/N) and transplanted them with NPM/ALK infected bone marrow cells. Eight IL-9 transgenic mice, serving as a control group, received pLXSN (vector only)-infected marrow. Reconstituted mice developed NPM-ALK-positive lymphomas, including lymphoblastic lymphomas of T-cell type (T-LB), mature and immature plasmacytoma (PC), and plasmoblastic/anaplastic diffuse large-B-cell lymphoma after about 19-20 weeks. The combined overexpression of NPM-ALK and IL-9 led to the transformation of murine lymphoid cells with accelerated and enhanced development of T-LB in 46% of the mice, which only very rarely occurs in IL-9 transgenic mice only. Of the 15 animals, five (33%) developed plasmacytic/plasmoblastic neoplasms, of which the most aggressive tumours share many features with anaplastic/plasmoblastic diffuse large-B-cell lymphoma on the basis of morphology, a characteristic growth pattern and ALK expression.

Animals↗

PubMed2003

Chemical carcinogens as foreign bodies and some pitfalls regarding cancer immune surveillance.

Interferon-gamma-receptor (IFN-gammaR)-deficient mice are more susceptible to tumor induction by methylcholanthrene (MCA) in comparison to control littermates. The cellular source of IFNgamma is not known, but the absence of T cells does not significantly increase the incidence of MCA-induced tumors. However, it appears that the presence of T cells in combination with unknown, perhaps environmental, factors can decrease MCA-induced tumor incidence, indicating that IFN-gamma of unknown origin contributes to the protective response. The current knowledge of cancer biology, immune regulation, and tumor-promoting effects of inflammation are difficult to reconcile with the concept of immune surveillance against non-virus-associated cancer. Analysis of the primary MCA-treated mouse indicates, as one protective mechanism, a tissue repair response against MCA-induced damage, in the course of which MCA is encapsulated and persists for long time in tumor-free mice, termed foreign-body reaction. The protection from DNA damage could simultaneously diminish tissue injury and malignant transformation. We argue that inhibition of MCA-induced carcinogenesis is mechanistically different from tumor transplantation immunity and that a longer latency in MCA-treated mice is unlikely due to T cell-mediated tumor recognition and selection of less immunogenic variants. We discuss that the IFNgammaR-dependent mechanism against MCA is unrelated to the original concept of T cell-mediated immune surveillance and that the increased spontaneous tumor incidence observed in some immune-deficient mice is likely to be explained by opportunistic infection and tumor-promoting chronic inflammation.

Animals↗

PubMed2003

The role of IFN-gamma in tumor transplantation immunity and inhibition of chemical carcinogenesis.

IFN-gamma contributes to the rejection of transplantable tumors and the inhibition of methylcholanthrene (MCA)-induced carcinogenesis by different mechanisms. In most tumor transplantation models, tumor rejection requires IFN-gamma receptor expression by host cells, but not by tumor cells. IFN-gamma produced by either CD4+ or CD8+ T cells acts on non-hematopoietic tumor stroma cells and, either directly or indirectly, induces angiostasis. This prevents rapid tumor burden and allows residual tumor cells to be eliminated. In some models, IFN-gamma also contributes to the destruction of existing tumor blood vessels. During MCA-induced tumorigenesis IFN-gamma is involved in the inhibition of MCA diffusion by encapsulation and reduction of DNA damage. This mechanism may primarily protect tissue from damage and simultaneously inhibit tumor development.

Animals↗

PubMed2002

Naive CD8(+) but not CD4(+) T cells induce maturation of dendritic cells.

We have shown previously that the generation of tumor-reactive CD8(+) cytotoxic T lymphocytes require qualitatively different signals from CD4(+) and CD8(+) T cells that most likely are provided to dendritic cells (DCs). This raises the question of whether the two T cell subsets are equally able to deliver the initial activation signal to DCs. Using ovalbumin as a model antigen we show that naive CD4(+) T cells cannot activate immature DCs and do not become activated, even though they recognize antigen on immature DCs. In contrast, naive CD8(+) T cells rapidly activate DCs and subsequently start to proliferate. This suggests that CD8(+) T cells contribute to DC activation prior to CD4(+) T cells and implies that CD8(+) T cells can provide help to CD4(+) T cells.

Animals↗

PubMed2002

Inhibition of methylcholanthrene-induced carcinogenesis by an interferon gamma receptor-dependent foreign body reaction.

The foreign body reaction is one of the oldest host defense mechanisms against tissue damage which involves inflammation, scarring, and encapsulation. The chemical carcinogen methylcholanthrene (MCA) induces fibrosarcoma and tissue damage in parallel at the injection site. Tumor development induced by MCA but not due to p53-deficiency is increased in interferon-gamma receptor (IFN-gammaR)-deficient mice. In the absence of IFN-gammaR, MCA diffusion and DNA damage of surrounding cells is increased. Locally produced IFN-gamma induces the formation of a fibrotic capsule. Encapsulated MCA can persist virtually life-long in mice without inducing tumors. Together, the foreign body reaction against MCA prevents malignant transformation, probably by reducing DNA damage. This mechanism is more efficient in the presence of IFN-gammaR. Our results indicates that inflammation and scarring, both suspected to contribute to malignancy, prevent cancer in certain situations.

Age Factors↗

PubMed2002

Increased tumorigenicity, but unchanged immunogenicity, of transporter for antigen presentation 1-deficient tumors.

The lack of transporter-for-antigen-presentation (TAP)-1 expression by tumor cells prevents the processing and presentation of MHC class I-restricted tumor antigens. This could affect T-cell-dependent tumor immunity in either the priming or the effector phase. We have established TAP1(+) and TAP1(-) tumor cell lines using ras-transformed NIH3T3 fibroblasts. Impaired TAP1 expression by tumor cells increased their tumorigenicity in immunocompetent, but not in T-cell-deficient, mice. For the generation of tumor immunity, TAP1 expression was not necessary on tumor cells used for vaccination. However, in previously immunized mice TAP1(+) tumor cells were more efficiently rejected than were TAP1(-) tumor cells. CD8(+) T cells infiltrated both TAP1(+)- and TAP1(-)-challenge tumors and were required for tumor rejection. In mixed tumor/lymphocyte culture, TAP1 expression by tumor cells significantly increased the IFN-gamma production of antigen-specific spleen cells from immunized, but not from naive, mice. Thus, the lack of TAP1 expression did not change the immunogenicity of tumor cells. It may enable tumor cells to escape T-cell recognition during the effector phase of an antitumor immune response.

3T3 Cells↗

PubMed2002

Cross-priming versus cross-tolerance: are two signals enough?

Depending on their state of maturation, dendritic cells (DCs) can cross-prime or cross-tolerize T cells. Mature DCs provide T-cell-receptor ligands (signal 1) and costimulatory molecules (signal 2), and activate T cells. Immature DCs provide signal 1, but not signal 2, and tolerize T cells. However, new data show that it is not the expression of costimulatory molecules alone that determines whether DCs induce immunity or tolerance, because mature DCs can induce tolerance also.

Animals↗