CXCL12 and breast cancer: Furthermore, CXCL12, an important promoter of bone metastasis in PCa, could be induced by an exosome-mediated HIF1α-dependent pathway, which created a pre-metastatic niche and promoted the progression of PCa metastasis.80 In breast cancer, large exosomes secreted from cancer cells were found to contain miR-122, which could remodel metabolism in the pre-metastatic niche to exacerbate metastasis.115 Breast cancer cells could suppress uptake of glucose by stromal cell in pre-metastatic niche of brain and lung, by transferring exosomes that carried enriched miR-122.