Background

The Research Group “GMP & T Cell Therapy” has been working on the identification of novel tumor antigen-specific CD4+ T cell epitopes that could be included as vaccine components in tumor immunotherapy approaches or used for immune-monitoring of cancer patients. Employing HLA transgenic mice, we were able to identify a panel HLA-DRB1*0301- and HLA-DRB1*0401-restricted CD4+ T cell epitopes specific for tumor associated differentiation antigens expressed in human melanoma and breast cancer, respectively. Moreover, a transplantable NY-BR-1 expressing breast cancer model could be established in HLA- DRB1*0401tg mice. Prompted by these studies we became interested in the interaction between tumor antigen specific CD4+ T cells and immune suppressive M2 like tumor associated macrophages (TAMs). We could demonstrate that activated CD4+ T cells when transferred into tumor bearing mice can repolarize M2 associated TAMs towards an immunostimulatory M1 phenotype, thus highlighting another tumor counteracting function of tumor antigen specific CD4+ T cells. Moreover, we noted that TAM polarization was accompanied by a change in the intracellular miRNA expression profiles and thus started to identify miRNAs involved in TAM polarization. Furthermore we have been investigating the function of miRNAs affecting the interaction between murine tumor cell lines and tumor antigen specific cytotoxic T cells (CTLs).

It has been shown that irradiation of a primary tumor can induce shrinkage of untreated tumors located outside of the irradiation field. This rarely, but consistently occurring “abscopal effect” can be reinforced upon combination of irradiation therapy with administration of antibodies against immunological checkpoint inhibitors. We are thus following the abscopal effects induced by combined radio-immunotherapy regimens in various murine tumor models.Importantly, we propose to extend these investigations to irradiation therapy with carbon ions. This novel irradiation modality is hallmarked by its focused release of destructive energy precisely on the targeted tumor, showing only minimal side effects on surrounding healthy tissue.

References

A complete and actualized listing of publications of the Eichmüller lab can be found on a separate website. PDF files are available on request for personal usage (see website).

Projects

The following projects are presently running in our lab.

Project 1: Targeting of M2-like TAMs by repolarizing miRNAs

Tumor associated macrophages (TAMs) are highlighted by functional plasticity enabling them to shift between various functional phenotypes ranging from M2-like macrophages with immunosuppressive function to immuno-stimulatory M1-like TAMs. Since the amount of intra-tumoral TAMs is generally dominated by M2-like macrophages, we propose to repolarize M2 like TAMs through introduction of M1-polarizing miRNAs directly into M2-like TAMs. For this purpose, two miRNA delivery systems are currently being developed: i) miRNA conjugated gold particles tagged with a M2 targeting structure and ii) viral delivery systems based on engineered measles virus strains recombinantly expressing the polarizing miRNAs. The miRNA delivery systems generated will be tested in vitro on M2-like bone marrow derived macrophages (BMDMs) and subsequently on TAMs isolated from tumor bearing mice. Finally, the therapeutic effect of the M2-targeting miRNA shuttle systems will be analyzed in tumor bearing mice after systemic administration.

Project 2: Boosting the abscopal effects of combined radio-immunotherapy approache

In this project, the radio-immunogenic effects of photon and carbonion irradiation are compared. First, both modalities are tested on various tumor cell lines in vitro. Therefore, alterations in the expression of immunomodulatory molecules in response to different irradiation regimens (various doses, fractionated or as single dose) are analyzed by qPCR and on protein level by FACS. Next, the abscopal effects induced among non-irradiated tumors upon irradiation of the primary tumor combined with systemic application of monoclonal antibodies against immune checkpoint inhibitors are investigated. Thus, the immune infiltrate of irradiated tumors and of non-irradiated regressing lesions will be analyzed in close detail applying FACS, qPCR, tetramer staining and singe cell sequencing. Boosting the abscopal effect by optimized radio-immunotherapy strategies might to improve the therapy of metastatic lesions making the application of chemotherapeutic drugs dispensable.

Project 3: miRNA impacting CTL susceptibility of melanoma cells

miRNAs are endogenous, small non-coding RNAs post-transcriptionally repressing gene expression by a mechanism known as RNA interference (RNAi). Thus, miRNAs can act as oncogenes or as tumor suppressors, respectively, depending on the gene encoded by the mRNA they target. We have shown that miR137 down regulates expression of the melanoma associated tumor antigen TRP-2 in human and murine melanoma cell lines. Notably, such modulation of tumor antigen expression might alter the susceptibility of the melanoma cell for recognition by tumor antigen-specific CTL, thereby creating link between miRNA expression in melanoma cells and tumor immuno-surveillance. Based on these results a miRNA library screen has been performed and identified miRNAs, which are able to modulate the susceptibility of tumor cells for CTL-mediated cytolysis. Presently, we determine the mRNA species targeted by the identified miRNAs. As result, miRNAs representing starting points for diagnostic and/or therapeutic interventions should become available.

Cooperations

Prof. Dr. Jessica Hassel / Prof. Dr. Enk (Dept. of Dermatology, University Hospital Heidelberg)
Prof. Dr. Magnus von Knebel-Döberitz (DKFZ, F210)
Prof. Dr. Rainer König (Jena University Hospital, Jena)
Prof. Dr. Dirk Jäger (NCT Heidelberg)
Prof. Dr. Martin Müller (DKFZ, F035)
Prof. Dr. Martin Löchelt (DKFZ, F030)
Prof. Dr. Rienk Offringa (DKFZ, D200)
Prof. Dr. Michael Platten & Dr. Isabel Poschke (DKFZ, D170, G808)
Prof. Dr. Stefan Rieken (University Hospital Göttingen, Radiology)
Prof. Dr. Florian Schütz / PD Dr. Christoph Domschke (Dept. of Gynecology, University Hospital Heidelberg)
Prof. Dr. Barbara Seliger (Inst. for Medical Immunology, University Hospital Halle)
Prof. Dr. Dr. Guy Ungerechts (DKFZ, F230)

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