Implantable pre-metastatic niches for the study of the microenvironmental regulation of disseminated human tumour cells

Survivors of cancer often carry disseminated tumour cells (DTCs); however, they do not relapse from treatment owing to DTC dormancy. Understanding how the local microenvironment regulates the transition of DTCs from a quiescent state to active proliferation could suggest new therapeutic strategies to prevent or delay the formation of metastases. Here, we show that implantable biomaterial microenvironments incorporating human stromal cells, immune cells and cancer cells can be used to examine the post-dissemination phase of tumour microenvironment evolution. After subdermal implantation in mice, porous hydrogel scaffolds seeded with human bone marrow stromal cells form a vascularized niche and recruit human circulating tumour cells released from an orthotopic prostate tumour xenograft. Systemic injection of human peripheral blood mononuclear cells slowed the progression of early metastatic niches. However, the rate of overt metastases did not change. Implantable pre-metastatic niches provide a new opportunity to study DTC activation and evolution to lethal metastasis, and could facilitate the development of effective anti-metastatic therapies.