Prof. Dr. Marina Kreutz
Department of Haematology and Oncology
University Hospital Regensburg
Franz-Josef-Strauss Allee 11
93042 Regensburg, Germany
Tel.: +49 (0)941 944 5587 Fax: +49 (0)941 944 5593
(for email please type firstname.lastname@example.org)
Area of Interest I: Tumor metabolism and immune cell function
As a consequence of malignant transformation tumor cells shown an altered metabolic phenotype. A link between tumor metabolism and cancer was first described many years ago by Warburg (aerobic glycolysis, "Warburg effect”) and this "glycolytic phenotype” seems to be necessary for the evolution of invasive human cancers. In addition, tumor cells have an altered amino acid metabolism, e.g. express high levels of tryptophan and L-arginine metabolizing enzymes. This leads to depletion of tryptophan and L-arginine and locally blocks T cell proliferation.
Our own findings indicate that the glycolysis end product lactate is found in the sera of tumor patients and inhibits immune cell function. In our laboratory, the interaction of immune cells with tumor cells is investigated in a tumor spheroid model. Spheroids are three dimensional tumor cultures and represent a model for non-vascularized tumor sites and metastases. We could show that different types of tumor spheroids suppress dendritic cell differentiation and T cell activation and identified lactic acid as one factor responsible for the modulation in the tumor environment. Therefore the characteristic energy metabolism of tumor cells leads to immune suppression and contributes to immune escape processes at the tumor site. We are currently characterizing the metabolom of different tumor entities and analyze the effects of tumor metabolites on immune cell function. A metabolic footprint of specific tumors will perhaps allow the identification of patient subsets responsive to immune therapy and modulation of the metabolic activity of tumor cells may increase T cell activation at the tumor site.
Area of Interest II: Vitamin D3 metabolism and immune cell differentiation
Blood monocytes migrate into the tissue where the specific microenvironment determines their fate, e.g., differentiation into the various types of tissue macrophages or dendritic cells. The active form of vitamin D, 1 alpha ,25-dihydroxyvitamin D3 ( 1,25 (OH)2 D3) is one possible factor which, at least in vitro, can induce the differentiation of macrophages, but inhibits dendritic cell differentiation. It also modulates the activity of B-and T-lymphocytes and seems to be involved in the generation of regulatory T cells.
The normal serum level of 1,25 (OH)2 D3 is relatively low (~10-10M), whereas that of 25-hydroxyvitamin D3 (25(OH)D3), the major circulating vitamin D metabolite, is about 1000-fold higher. Synthesis of 1,25 (OH)2 D3 from its precursor 25(OH)D3 normally occurs in the kidney, however, we and others have shown that macrophages and dendritic cells can also convert 25(OH)D3 into 1,25(OH)2D3. This production most likely does not exert systemic effects but rather has a local paracrine function. We are interested in the immune regulatory potential of 1,25 (OH)2 D3 and could show that low 25 (OH) D3 and 1,25 (OH)2 D3 serum levels are linked to the occurrence of graft versus host disease/GvHD. Currently we investigate polymorphisms of vitamin D metabolizing enzymes (CYP27A1 and CYP27B1) and their relevance for GvHD.
The group is supported by: Deutsche Forschungsgemeinschaft (German Research Society), Wilhelm Sander-Stiftung and the Regensburg Research Foundation (ReForM).