Further, brain metastases derived from multiple breast cancer cell lines showed more than 15 fold increase of Rab11b expression compared with cultured cells (Fig. 2c, d), with no change in Rab11a or Rab25 levels (Supplementary Fig. 3a), suggesting the brain metastatic microenvironment specifically influences Rab11b expression. This evidence concerns the gene RAB25 and breast cancer.