RAB22A and cancer: It is well known that cancer cells secrete factors contributing to the formation of pre-metastatic niche by stimulating the bone marrow-derived cells (BMDCs) mobilization or inducing the extracellular matrix remodeling.14,23,24,30 To investigate the role of exosomal Rab22a-NeoF1 fusion protein in the formation of pre-metastatic niche, we pre-educated tumor-free mice by injection of the CM, as illustrated in Fig. 5a.