|The development and implementation of novel technologies to investigate oxygenation initially requires in-depth correlative studies relative to standard experimental approaches. Current techniques (in relation to molecular and mechanistic effects of tumor oxygenation) include the invasive detection of endogenous hypoxia-induced marker proteins, such as HIF-1/2a, Glut1 and CAIX; exogenous hypoxia-tracers such as pimonidazole and misonidazole, probing tumor hypoxia below 10 mmHg; HypoxiSense680, probing hypoxia-induced CAIX; and genetically modified cells and mouse models to probe/visualize hypoxia in tumor cells and the stroma. These techniques are partly established in the preclinical KFSP-related laboratories. We will use tumor clamping of preclinical allo- and xenograft models to standardize the novel imaging technologies with the current technologies monitoring tumor oxygenation.|
Next to these validation/correlation-studies we aim for a better understanding of the interplay between tumor oxygenation and inflammation, two major environmental conditions that govern the "aggressiveness" of a tumor, resulting in increased metastasis and therapy resistance. Tumor angiogenesis, intravasation and extravasation, and even the preparation of the pre-metastatic niche in distal organs have been reported to be enhanced by tumor hypoxia. Interestingly, each of these processes is strongly enhanced by inflammation, another hallmark of cancer progression and a strong oxygen sink. Special emphasis will be put on the development of techniques to image the heterogeneous oxygenation of cancer cells, surrounding stroma cells and infiltrating leukocytes. We have established genetically-modified cancer cell lines to determine the relevance of major effectors of hypoxia (HIF-1a and HIF-2a subunits of hypoxia-inducible factor HIF) and inflammation (p65 subunit of nuclear factor NF-KB) and to monitor related signalling cascades with respective luciferase-based reporter genes. Using different transgenic mice models we will assess tumor stroma- and leukocyte-related hypoxia, estimate tumor macrophage infiltration and determine the contribution of inflammatory monocytes to deregulated tumor oxygenation in the growing tumor and in response to treatment. Indeed, the risk for a large number of cancers is known to be associated with chronic inflammation of the pre-neoplastic tissue. Leukocyte infiltration and changes in tumor oxygenation will also occur following cancer cell death in the course of tumor chemo- and radiotherapy. The effects of tumor-targeted chemotherapy or radiotherapy will be assessed both on tumor cell survival and changes in tumor stroma (in collaboration with M. Pruschy). We will use IVIS fluorescence and bioluminescence measurements next to the novel biophotonics methodologies to analyse tumor oxygenation, perfusion, progression, macrophage infiltrations and metastasis formation and will complement these dynamic in vivo-detection methodologies by classic immunohistochemistry and ex vivo FACS quantification.
The results of these studies will deepen the understanding of the results of the clinical studies and consequently will enable to formulate new hypotheses and to further improve therapy.