Mechanisms of metastatic outgrowth of spontaneous bone marrow metastases of human prostate cancer cells in vivo

• Applicant: Professor Tobias Lange, Ph.D.
• Subject Area: Hematology, Oncology ; Nuclear Medicine, Radiotherapy, Radiobiology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 491128300

In the first µBONE funding period, we developed a mouse model that goes beyond the state of the art and makes it possible for the first time to model the cascade of bone metastasis of human prostate carcinoma (PCa) cells in vivo as a whole, starting with the growth of primary tumors and ending with the spontaneous formation of disseminated tumor cells as well as outgrowing bone metastases. We want to use this model in the second funding period to further investigate the mechanisms of PCa bone metastasis. In our model, the xenograft primary tumors influence bone remodelling and changes in bone remodeling (e.g. due to castration) in turn influence the formation of bone metastases.Dickkopf-related protein 1 (DKK1) is a factor that both regulates bone remodelling and - according to previous work on other tumor entities - controls the outgrowth of metastases. In our preliminary work, shRNA-mediated depletion of DKK1 alters EMT/ MET gene expression in PCa cells and impairs their migration behavior in vitro. Knockout of DKK1 receptors Krm1 and Krm2 leads to high bone mass in NSG mice and promotes the growth of spontaneous PCa bone metastases in vivo. Xenograft sublines from primary tumors, lung metastases and bone metastases show divergent clonal heterogeneity and differential metastatic potential after re-xenografting into our model.Our goals for the second funding period are to further explore and translate our findings on the functional role of the DKK1 (co)-receptor axis in the metastatic outgrowth of human PCa bone metastases. After completion of the current experiments on the role of the DKK1 co-receptors Krm1 and Krm2, we will analyze the role of the main receptor Lrp5 for the outgrowth of bone metastases and furthermore inhibit DKK1 in the tumor cells themselves. This will be done using a humanized DKK1 monoclonal antibody (hDKN-01), which is currently being tested in a phase 1-2 clinical trial in PCa patients. In addition, we will validate our findings using a novel patient-derived xenograft (PDX) model recently established in our group in Krm1/2-KO and/or Lrp5 mutant mice and/or by treatment with hDKN-01. Furthermore, we will analyze in detail the functional and molecular differences of our xenograft primary tumor, lung metastasis and bone metastasis sublines. Finally, we will exploit our unique resource of xenograft primary tumors and corresponding spontaneous bone metastases by performing laser capture microdissections on primary tumor and metastatic lesions, followed by differential proteomics analyses. With the latter two approaches, we aim to identify new functional drivers of metastatic outgrowth of PCa bone metastases, which are planned to be clinically validated.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2084: µBONE: Colonization and interaction of tumor cells within the bone microenvironment
• International Connection: Australia
• Cooperation Partner: Dr. Arun Everest-Dass