Bone marrow microenvironment in cancer patients: immunological aspects and clinical implications

The bone marrow (BM) of cancer patients is considered an essential secondary lymphoid organ with substantial impact on tumor cell dissemination and tumor–immune responses. Recent advances in the understanding of BM/primary tumor crosstalk, homing processes, premetastatic niche formation, tumor cell dormancy, and ultimately, identification of the BM micromilieu cytokines, chemokines, and growth factors may provide the basis for the development of targeted therapeutic strategies potentially rendering primary cancers and cancer bone metastases more susceptible to chemotherapy. The present review aims to dissect the individual components of the BM microenvironment in cancer patients, compare it to the healthy BM, and discuss its impact on interactions between the tumor and the immune system.