Therapy resistance of melanoma through modulation of the tumor stroma by B cells

The tumor microenvironment (TME) critically controls therapy responses of tumors. B cells are part of the TME in melanomas and we have recently shown that, after state-of-the-art inhibitor therapies, tumor associated B cells (TAB) secrete inflammatory cytokines and growth factors to induce therapy resistance via a bi-directional communication with human melanoma cells. In a clinical pilot trial, we have shown anti-tumor responses through B cell-targeting in several end-stage metastatic melanoma patients who became resistant to inhibitor therapies. Cells of the TME not only signal to tumor cells but also to each other and we hypothesize that TAB profoundly change the TME via interactions with other cell types to indirectly induce therapy resistance in tumor cells. A deeper knowledge of these indirect mechanisms could contribute to improve state-of-the-art inhibitor therapies and to develop novel therapies, respectively. We will run state-of-the-art proteomics and genomics analyses and use novel bioinformatic algorithms and systems biology tools on therapy-resistant melanoma tumors to generate a systems biology map of the complex interactions of TAB with other cell types of the TME. This interaction map shall be refined by functional assays in cell culture models with 3D organotypic reconstructs, that simulate interaction of tumor cells, the TME and TAB in the context of the organ most frequently affected by melanoma, i.e. the skin. The most innovative aspect of the proposal includes the extraction of a functionally refined systems biology view of the TAB-modified TME in melanoma for prediction of novel therapy targets with improved analytical tools, an important contribution for the development of precision medicine approaches in the treatment of cancer. To accomplish our goal, we have set up an interdisciplinary team of investigators with complementary expertise that covers all aspects of the project. We have profound expertise in bioinformatics and systems biology analyses (Johannes Griss, Med. Univ. of Vienna; Jörg Menche, CeMM, Vienna); in secretomics, (phospho)proteomics (Markus Hartl, Univ. of Vienna); and RNAseq (Christoph Bock, CeMM) technologies; and in melanoma immunology, cell biology and 3D cell cultures and organotypic reconstructs (Stephan N. Wagner, Med. Univ. of Vienna, Meenhard Herlyn, Wistar Inst., Philadelphia).

In this project, we worked with numerous scientists using the latest methods of immunology, molecular biology and proteomics to identify and describe these complex interactions in more detail in order to find new ways to improve current immunotherapies. In a first analysis of the interaction of tumor cells, in this case human melanoma cells, with B cells, we were the first to show that melanoma cells alter the appearance type and function of B cells in such a way that they can attract and activate tumor-fighting immune cells, namely T cells. Thus, the presence of B cells in melanoma can not only enhance the effect of current immunotherapies, but also predict the response to these therapies. B cells are formed in mature lymphatic structures. This occurs either directly in the tumor or in the adjacent lymph node tissue, from where the B cells can migrate into the tumor. Our data indicate that most lymphoid structures in melanoma are not fully mature, in contrast to those in lymph node tissue. Thus, future approaches to improve immunotherapies should incorporate the full maturation of lymphoid structures in tumors. We have been able to publish this work in peer-reviewed publications in high-ranking, renowned journals. We are currently analyzing the interactions of B cells with other cell types from the melanoma microenvironment. Our work indicates a significant change in the phenotype and function of individual cell types, which may also be of great importance for the improvement of immunotherapies. We will be able to summarize these results in two further manuscripts in the near future.