We have suggested that increased levels of BK and ATP point at a compensatory effect for metastasis of tumor cells to the BM, explaining why this tissue is the most common site for recurrence of several cancers (Coleman, 2001; Bacci et al., 2006), even when SDF-1 levels diminish after chemotherapy decreases due to an induced proteolytic environment (Ratajczak et al., 2013). Here, CXCL12 is linked to cancer.