There is an utmost medical need to develop strategies for the elimination of cancer cells from the bone marrow (BM) because it represents the prime location in which cancer cells persist. Alarmingly, the mortality of early-stage breast cancer patients is twice as high when disseminated tumor cells (DTC) are present in their BM compared to patients without DTC. This means that approximately 50.000 women with curable breast cancer die per year in the EU because of relapse attributed to DTC. Similarly, in leukemia established treatments are unable to completely eradicate the neoplastic cells in many cases. This persistence of malignant cells is termed minimal residual disease (MRD). MRD represents a major health problem for millions of patients with solid tumors and leukemia alike because it mostly precludes cure. In light of the failure of conventional therapies it is therefore of paramount importance to develop novel strategies to eradicate cancer cells from the BM.
Hematologic and solid tumor cells abuse the BM as “safe haven” to survive anti-cancer treatments. Although these cells are of different tissue origin they use partially overlapping mechanisms to ensure their survival in the BM. The majority of existing literature refers to similar mechanisms between both malignant cell types regarding interaction with important cell populations implicated in bone remodelling. In contrast, we have very little knowledge whether solid and hematologic cancer cells differ in their interaction with immune cells in the BM. Gaining these insights is crucial for developing therapeutic approaches to enable the immune system to combat solid vs. hematologic cancer cells in the BM.
Very little knowledge exists about anti-cancer immune responses in the BM of cancer patients and the interaction between immune cells and immune-modulatory BM stroma cells. Furthermore a relevant knowledge gap is whether immune-checkpoint blockers can elicit anti-cancer immune responses in the BM. The challenge is to understand the specific immune microenvironment in the BM by integrating information from the hematology, oncology and basic research fields. Thus, this proposal aims to develop multidisciplinary bench-to-bedside and reverse approaches that will enable a comprehensive understanding of the immune microenvironment and novel strategies to harness the immune system to combat cancer in the BM will emerge.
