Exosomal miR-19a and IBSP cooperate to induce osteolytic bone metastasis of estrogen receptor-positive breast cancer

Bone metastasis is a major complication of breast cancer (BC) and ER+ tumors have a higher incidence of bone metastasis than ER− tumors. Here, the authors report that miR‐19a in exosomes and the bone matrix protein, IBSP, are upregulated and secreted by bone tropic ER+ BC cells, where they cooperatively induce osteoclastogenesis and promote bone colonization.