Stromal-cell and cancer-cell exosomes leading the metastatic exodus for the promised niche.

Exosomes are thought to play an important role in metastasis. Luga and colleagues have described the production of exosomes by stromal cells such as cancer-associated fibroblasts that are taken up by breast cancer cells and are then loaded with Wnt 11, which is associated with stimulation of the invasiveness and metastasis of the breast cancer cells. Previous studies have shown that exosomes produced by breast cancer cells are taken up by stromal fibroblasts and other stromal cells, suggesting that exosomes are agents of cross-talk between cancer and stromal cells to stimulate metastasis. Imaging of exosomes by labeling with fluorescent proteins will enlighten the process by which exosomes enhance metastasis, including premetastatic niche formation.