Cancer Cell Dissemination and Homing to the Bone Marrow in a Zebrafish Model

Advancement of many solid tumors and hematologic malignancies is frequently characterized by dissemination and homing of cancer cells to the bone marrow (BM). Methods to quantitatively characterize these key steps of the metastatic cascade in mammalian models are currently limited and do not offer opportunities to perform rapid, large-scale genomic, or drug screening. Because of their optical clarity, we used zebrafish to develop an in vivo model of cancer cell dissemination and homing to the BM. We performed intracardiac injection of multiple myeloma (MM) cells derived from human BM or cell lines and monitored their migration to the caudal hematopoietic tissue (CHT), the region where hematopoiesis occurs in the zebrafish embryo, which recapitulates a BM-like niche. Transcriptomic analyses confirmed that MM cells homing to the CHT displayed gene-expression differences compared with MM cells outside of the CHT, including significant enrichment for genes known to regulate interleukin-6 (IL6) signaling, cell adhesion, and angiogenesis. Collectively, our findings point to the zebrafish as a valuable model in which to study cancer cell homing to the hematopoietic niche and to establish a screening platform for the identification of factors and mechanisms contributing to the early steps of bone metastasis.