Biomedical subjects

David Schrama

Publications and source records attributed to David Schrama.

At least 19 recordsLinked to original sources

PubMed2006

Dendritic cell based antitumor vaccination: impact of functional indoleamine 2,3-dioxygenase expression.

BACKGROUND: Recent reports have demonstrated that the enzyme indoleamine 2,3-dioxygenase (IDO) is upregulated in human dendritic cells (DCs) upon in vitro maturation. IDO is supposed to convey immunosuppressive effects by degrading the essential amino acid tryptophan, thereby downregulating T-cell functions. Hence, we evaluated IDO expression in DC preparations used for therapeutic DC vaccination and its in vivo effects. PATIENTS, METHODS AND RESULTS: IDO expression was detected by real-time-PCR in a series of human clinical grade DCs (n = 28) prior to vaccination of advanced melanoma patients (n = 11). These analyses revealed an intra- and interpersonal variation in IDO mRNA levels. IDO was strongly upregulated in human DCs on RNA and on protein level upon in vitro maturation by Interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha), Interleukin-6 (IL-6) and Prostaglandin E2 (PGE2) over a time course of 24 h. The enzymatic activity of induced IDO was demonstrated by measuring tryptophan degradation. Moreover, in biopsies obtained 24 h after application of the DC vaccine a prominent infiltrate of IDO-positive cells was observed by immunohistochemistry. The inflammatory infiltrate of these sites stained positive for the transcription factor Forkhead box P3 (FoxP3), suggesting an IDO-mediated induction of regulatory T-cells. All analysed melanoma patients (n = 11) receiving DC based immunotherapy exhibited rapid disease progression with a short overall survival due to advanced tumour stage. CONCLUSION: The presented observations suggest a potential clinical relevance of IDO expression in DC-based therapeutic vaccines via the attraction or induction of FoxP3(+) T-cells.

Adult↗

PubMed2006

Molecularly targeted therapy for melanoma: current reality and future options.

Effective therapy for melanoma remains an unmet goal, with most traditional therapies representing inadequate trade-offs among the several goals of specificity, efficacy, and toxicity. Targeted molecular therapeutics are tailored to genetic abnormalities that are associated with tumor progression. Modulation of aberrant signaling pathways in cancer cells has the potential to provide more effective and potentially nontoxic therapy for a broad range of cancers, including melanoma. Among the possible targets in melanoma are the Ras-MAPK and PI3K/AKT signal transduction pathways, the proteasome, histone deacetylases, methyltransferases, and melanoma-induced angiogenesis.

Angiogenesis Inhibitors↗

PubMed2006

Expression pattern of the lymphatic and vascular markers VEGFR-3 and CD31 does not predict regional lymph node metastasis in cutaneous melanoma.

Malignant melanoma of the skin preferentially metastasises via the lymphatic system. Novel molecular biomarkers, which are involved in malignant transformation, proliferation, angiogenesis and lymphangiogenesis, are currently under investigation to elucidate the risk for lymph node metastasis. To this end, the vascular endothelial growth factors VEGF-C and VEGF-D have been identified to promote lymphangiogenesis and lymphatic spread through activation of its receptor, Vascular endothelial growth factor receptor-3 (VEGFR-3). Prompted by this assumption, we estimated the degree of lymphangiogenesis by semiquantitative immunohistochemical analysis of the expression of VEGFR-3 and the panvascular marker CD31 in primary cutaneous melanoma (n=26) and correlated these findings with the sentinel lymph node (SLN) status. The cohort was selected for matched prognostic markers in SLN-positive and SLN-negative patients. In contrast to other studies, we observed an inverse correlation between expression of these markers with lymph node metastases. Additionally, no difference between intratumoral versus peritumoral CD31- or VEGFR-3 expression on blood vessels versus lymphatic capillaries could be detected. Interestingly, VEGFR-3 upregulation was not restrained to vascular structures but also appeared on tumor cells. In summary, in our series VEGFR-3/CD31 immunohistochemical staining of primary melanoma does not serve as a valid marker to predict lymph node involvement. As lymphatic spread is a complex, multi-step process, several different biomarkers have to be combined to define new prognostic subgroups in cutaneous melanoma.

Aged↗

PubMed2006

Expression of the NKG2D ligand UL16 binding protein-1 (ULBP-1) on dendritic cells.

Innate and adaptive immunity have not evolved separately. In this regard, the NKG2D molecule first identified on NK cells and classified as an activating NK cell receptor is also an important receptor for CD8(+) T cells. Functional analyses of human NKG2D and its ligands, i.e. UL16 binding proteins (ULBP) and MHC class I chain-related (MIC), have so far focused on immune cell-target cell situations because of the expression of NKG2D ligands on infected, stressed or transformed cells. Here, however, we address a possible function of NKG2D/ULBP-1 during the initiation of T cell responses. ULBP-1 can be detected on mature dendritic cells both in situ in the T cell areas of lymph nodes as well as in vitro after artificial maturation. FCM analysis further demonstrated that although NKG2D is expressed to some degree on all analyzed T cell subsets from peripheral blood, in vitro stimulation of T cells results in up-regulation of NKG2D on proliferating T cells. Using the sentinel lymph nodes of primary melanoma as a model for induction of defined T cell responses in vivo, we were able to demonstrate the expression of NKG2D on melanoma-associated antigen-specific T cells. Thus, our results suggest a role for NGK2D-ULBP-1 in the induction or reactivation of T cell responses.

CD8-Positive T-Lymphocytes↗

PubMed2006

Antibody targeted drugs as cancer therapeutics.

Treatment of cancer is a double-edged sword: it should be as aggressive as possible to completely destroy the tumour, but it is precisely this aggressiveness which often causes severe side effects - a reason why some promising therapeutics can not be applied systemically. In addition, therapeutics such as cytokines that physiologically function in a para- or autocrine fashion require a locally enhanced level to exert their effect appropriately. An elegant way to accumulate therapeutic agents at the tumour site is their conjugation/fusion to tumour-specific antibodies. Here, we discuss recent preclinical and clinical data for antibody-drug conjugates and fusion proteins with a special focus on drug components that exert their antitumour effects through normal biological processes.

Animals↗

PubMed2006

Cytotoxic T cells.

The immune system is a complex arrangement of cells and molecules that preserve the integrity of the organism by elimination of all elements judged dangerous. Within the immune system, a humoral and a cellular as well as an innate and an adaptive arm can be differentiated. The key players of adaptive cellular immune responses are T lymphocytes in general and, for the effector function, cytotoxic T lymphocytes (CTLs) in particular. T lymphocytes arise in the bone marrow and migrate to the thymus for maturation. During this process, T cells somatically rearrange gene segments, eventually leading to the expression of a unique antigen-binding molecule, the T-cell receptor (TCR). This receptor allows them to monitor all cells of the body, ready to destroy any cell posing a threat to the organism. Cytotoxicity is exerted directly through the Fas or perforin pathway and/or indirectly by the release of cytokines. Obviously, the activity of such a potent cell is tightly regulated. Indeed, a predominance of stimulatory over inhibitory signals is required for effective immune responses to pathogens, and a predominance of inhibitory over stimulatory signals is required for maintenance of self-tolerance. Still, several situations occur in which an inappropriate CTL response leads to either autoimmune disease or persistence of pathogens.

Autoimmune Diseases↗

PubMed2006

Absence of classical MAP kinase pathway signalling in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is a highly metastatic skin tumor. To assess the relevance of the Ras/Raf/MEK/MAP kinase pathway, we analyzed for activating B-Raf mutations and we elucidated the presence of the Raf Kinase Inhibitor Protein (RKIP) and extracellular signal-regulated kinase (ERK) as well as the phosphorylation status of ERK. All MCC samples were negative for the B-Raf(V600E) mutation. Remarkably, RKIP, which was shown to interfere with the activation of MEK by Raf, was highly expressed in primary as well as in metastatic MCC. Immunohistochemical analysis of the phosphorylation status of ERK revealed in 42 out of 44 samples a complete lack of activated ERK in the tumor cells although ERK is expressed; in the two positive cases phosphorylated ERK was restricted to a minor fraction of the tumor cells. Western blot analysis of three MCC-derived cell lines revealed in one case the pattern present in situ (i.e. high RKIP expression and complete absence of phosphorylated ERK). In summary, our data demonstrate the inactivity of the classical MAP kinase signal transduction pathway in MCC, which seems to be because of lack of activation as well as active deactivation. These findings should be accounted for in future therapeutic approaches for this tumor.

Androgen-Binding Protein↗

PubMed2006

[New therapeutic approaches for solid tumors: histone deacetylase, methyltransferase and proteasome inhibitors].

Recent results from basic and translational research on tumor genesis and progression establish the basis for future therapeutic approaches. Targeted therapeutics are tailored toward the molecular abnormalities that cause tumor progression and could potentially provide an effective, non-toxic therapeutic approach in a broad range of cancers including melanoma. Cancer is as much a (cyto)genetic disease as it is an epigenetic disease. Indeed, the fate of the cell depends on a delicate balance between expression and repression of genes. The notion that drastic changes in DNA methylation and histone modifications are present in a variety of human tumors has prompted the development and characterization of epigenetic drugs. Inhibitors of histone deacetylases and methyltransferases as well as of the proteasome are covered in this review.

Antineoplastic Agents↗

PubMed2006

New insights into the molecular biology and targeted therapy of cutaneous T-cell lymphomas.

Cutaneous T-cell lymphoma is an extra-nodal non-Hodgkin lymphoma of mature T cells. These tumor cells home to and persist in the skin,producing a broad spectrum of clinical entities. Recent results of basic research on tumor biology and tumor immunology as well as molecular genetics of cutaneous T-cell lymphoma have fostered the development of new therapeutic approaches. Several clinical trials testing these targeted therapies have shown encouraging results. This article provides an overview of recent research developments and therapeutic strategies for cutaneous T-cell lymphoma.

Animals↗

PubMed2005

Tumor stroma-associated antigens for anti-cancer immunotherapy.

Immunotherapy has been widely investigated for its potential use in cancer therapy and it becomes more and more apparent that the selection of target antigens is essential for its efficacy. Indeed, limited clinical efficacy is partly due to immune evasion mechanisms of neoplastic cells, e.g. downregulation of expression or presentation of the respective antigens. Consequently, antigens contributing to tumor cell survival seem to be more suitable therapeutic targets. However, even such antigens may be subject to immune evasion due to impaired processing and cell surface expression. Since development and progression of tumors is not only dependent on cancer cells themselves but also on the active contribution of the stromal cells, e.g. by secreting growth supporting factors, enzymes degrading the extracellular matrix or angiogenic factors, the tumor stroma may also serve as a target for immune intervention. To this end several antigens have been identified which are induced or upregulated on the tumor stroma. Tumor stroma-associated antigens are characterized by an otherwise restricted expression pattern, particularly with respect to differentiated tissues, and they have been successfully targeted by passive and active immunotherapy in preclinical models. Moreover, some of these strategies have already been translated into clinical trials.

Animals↗

PubMed2005

Therapeutic efficacy of tumor-targeted IL2 in LTalpha(-/-) mice depends on conditioned T cells.

An effective immunological eradication of tumors by the adaptive immune system depends on T cell priming, expansion of specific T cells and their effector function. It has been shown that either step may be impaired in the tumor-bearing host, and several strategies have been used to improve antitumor immune responses. In this regard, tumor-targeted IL2 therapy leads to the destruction of established melanoma metastases in fully immune competent mice as previously demonstrated. This effect has been attributed, but never directly confirmed, to the boost of antigen-experienced T cells. To this end, we demonstrate the absence of any antitumor effect of targeted IL2 in mice characterized by an impaired priming of T cell responses. Notably, in these animals tumor-targeted IL2 therapy induced tumor regression only after adoptive transfer of tumor-conditioned splenocytes. A detailed analysis revealed that T cells present within the transferred splenocytes were actively participating in the immune response as these were clonally expanded after targeted IL2 therapy. In summary, we demonstrate here that in LTalpha(-/-) mice lacking sufficient numbers of tumor-specific T cells only the passive transfer of such cells prior to therapy restores the efficacy of tumor-targeted IL2 therapy. Thus, the antitumor effect of tumor-targeted IL2 is indeed based on the boost of pre-existing T cell responses.

Animals↗

PubMed2005

Identification of identical TCRs in primary melanoma lesions and tumor free corresponding sentinel lymph nodes.

It is generally believed that priming of efficient T-cell responses takes place in peripheral lymphoid tissues. Although this notion has been rigidly proven for infectious diseases, direct evidence for lymph node priming of in vivo T-cell responses against tumors is still lacking. In the present study, we conducted a full and nonbiased comparison of T-cell clonotypes in melanoma lesions and corresponding sentinel lymph nodes. Whereas most tumor lesions comprised a high number of T-cell clonotypes, only a small number of clonally expanded T cells were detected in the draining lymph nodes. Comparative clonotype mapping demonstrated the presence of identical T-cell clonotypes in the tumors and the respective sentinel lymph nodes, only when tumor cells were present in the latter. However, taking advantage of clonotype specific PCR amplification, TCR sequences representing clonally expanded T cells at the tumor site could be detected in the lymph nodes draining the tumors even in the absence of tumor cells. Evidence for the tumor-specific characteristics of these cells was obtained by in situ staining with peptide/HLA class I complexes demonstrating the presence of MART-1/HLA-A2- and MAGE-3/HLA-A2-reactive T cells at the tumor site, as well as in the draining lymph node. Our data indicate that T-cell responses to melanoma are primed in the sentinel lymph node by cross presentation of tumor antigens by dendritic cells.

Adult↗

PubMed2005

Cytoplasmic and nuclear expression of survivin in melanocytic skin lesions.

Survivin, a member of the inhibitors of apoptosis protein family, regulates both cellular proliferation and apoptotic cell death. While the human survivin gene is highly expressed in the developing fetus, in adults its expression is restricted to highly proliferating normal tissues and neoplastic tumors tissues. In the present study, we compared the expression of survivin in melanoma and benign melanocytic lesions such as junctional, compound, dermal, congenital, blue and spitz nevi. This analysis reveals a heterogeneous expression of survivin with respect to both the intensity, frequency and cellular localization. In junctional, compound and blue nevi, survivin was present in nuclear localization, whereas in spitz nevi survivin was detectable in the cytoplasm. In dermal and congenital nevi, survivin was present in both localizations with predominance of the nuclear compartment. Interestingly, this distribution was similar to that observed in primary melanoma; whereas in metastatic melanoma the predominance of the nuclear localization of survivin was lost. Our data demonstrate that although survivin is expressed in a large number of benign nevi, the balance between its cytoplasmic and nuclear expression was immensely heterogeneous between lesions with suspected different developmental origins.

Cell Nucleus↗

PubMed2005

[Kinase inhibitors for the therapy of malignant melanoma].

Recent results from basic and translational research on the causes and mechanisms of melanoma genesis and progression will impact on future therapeutic approaches. The increasing understanding of the molecular pathology of malignant disease and the detailed analysis of the signal transduction pathways involved allows specific intervention with these oncogenic events. These interventions address the molecules associated with or responsible for the malignant transformation and have therefore been termed "targeted therapy". The present review focuses on the therapeutic options involving modulation of the Ras/MAPK- and PI3K/AKT-signal transduction pathways.

Animals↗

PubMed2004

Circulation and homing of melanoma-reactive T cells to both cutaneous and visceral metastases after vaccination with monocyte-derived dendritic cells.

Anticancer immune therapies aim at the induction of tumor-specific T cells, which ultimately should kill tumor cells. The effector cells should, therefore, not only exert cytotoxic activity but also home to and infiltrate the tumor site. Hence, monitoring of immune modulating therapies should not be restricted to the circulating pool of peripheral blood mononuclear cells (PBMC) but also include tumor-infiltrating lymphocytes (TIL), as well as the correlation of these findings to the clinical course. We report here on the longitudinal immunologic workup of a melanoma patient who developed remarkably potent ex vivo detectable antimelanoma cytotoxic T-cell (CTL) responses after vaccinations with autologous peptide-pulsed dendritic cells. Such potent CTL responses to multiple tumor antigens have, to the best of our knowledge, not been described previously in melanoma patients, neither spontaneously nor after any therapy. This patient first experienced a transient response to therapy but finally succumbed to disease progression and died. Progression was associated with the decline of the numbers of tumor-reactive T cells in circulation and at skin metastases in addition to the loss of MHC class I antigens. The immunologic analysis revealed that fully functional tumor-specific T cells were present in the peripheral blood of this patient during the phase of a relatively stable disease, and in situ tetramer staining demonstrated that these cells were also accumulated at cutaneous and visceral tumor sites. Furthermore, comparative clonotype mapping of PBMC and TIL depicted an overlapping TCR repertoire usage among these 2 compartments. Since strong CTL responses as observed in this patient are the goal of cancer vaccination but are so far only rarely observed, the thorough analysis of patients exhibiting either exceptional clinical and/or immunologic responses appears critical to understanding how vaccine therapies work and can be further improved.

Aged↗

PubMed2004

Shift from systemic to site-specific memory by tumor-targeted IL-2.

IL-2 has been approved for treatment of patients with cancer. Moreover, it has been used as a component of vaccines against cancer. In this regard, we have recently demonstrated that dendritic cell-based peptide vaccination in mice required IL-2 to mount an effective immune response against established melanoma metastases. In this study, we confirm this observation by use of tumor-targeted IL-2. However, the development of a protective systemic memory was substantially impaired by this measure, i.e., mice, which successfully rejected s.c. tumors of B16 melanoma after vaccination with dendritic cells pulsed with tyrosinase-related protein 2-derived peptides plus a boost with targeted IL-2, failed to reject a rechallenge with experimental pulmonary metastases. Detailed analysis revealed a change in the distribution of the tumor-reactive T cell population: although targeted IL-2 expanded the local effector population, tyrosinase-related protein 2-reactive T cells were almost completely depleted from lymphatic tissues.

Animals↗

PubMed2004

T-cell clonotypes in cancer.

Cells of the immune system spontaneously recognize autologous tumor cells and T cells are believed to be the main effector cells for the immune surveillance of cancer. Recent advances in our understanding of basic and tumor immunology together with methodological developments implies that tumor specific T cells can now be studied functionally, phenotypically as well as molecularly. T cells recognize peptide antigens in the context of MHC molecules through the clonally distributed T-cell receptor (TCR), thus, the clonal distribution of the TCR offers the means to detect and track specific T cells based upon detection of the unique TCR. In this review, we present and discuss available data on TCR utilization of tumor specific T cells in murine models as well as spontaneous and treatment induced anti-tumor T-cell responses in humans.

Journal Article↗

PubMed2004

Characterization of mouse MAGE-derived H-2Kb-restricted CTL epitopes.

Immunogenic peptide epitopes from tumor-associated antigens serve as targets for cellular immune responses in numerous clinical trials for therapeutic vaccinations. From these it became evident that prevailing questions can only be addressed in animal models. Hence, problems arise from the fact that while for human melanoma many different immunogenic peptide epitopes are known, for mouse melanoma the available selection is very restricted. To overcome this limitation, we applied reverse immunology to identify Kb-restricted epitopes derived of mouse MAGE. Two epitopes which bind strongly to Kb were selected to test for their immunogenicity in vivo. Spleen cells from mice vaccinated by intradermal injection of mature dendritic cells pulsed with these peptides displayed reactivity to the respective epitopes as measured by enzyme-linked immunospot assays and tetramer staining. The processing and presentation of these epitopes was evident by the killing of melanoma cells by the vaccination-induced T cells. Moreover, intravenous challenge with syngeneic melanoma cells demonstrated the protective immunity induced by this vaccination. In summary, we demonstrate the immunogenicity of two Kb-restricted peptide epitopes derived from mouse MAGE proteins which may serve as valuable tool for preclinical evaluation of vaccination strategies.

Animals↗