Treg numbers are increased in prostate cancer patients with bone metastasis [183], and this may be due in part to active recruitment and retention of Tregs in the bone marrow by CXCR4/CXCL12-mediated signaling [184], a pathway that is often also upregulated in DTC [185,186,187]. Here, CXCR4 is linked to Familial prostate cancer.