Thus, MICs probably express estrogen receptor (ER), progesterone receptor (PR), placental alkaline phosphatase (PLAP), and erythropoietin receptor and employ the same CXCR4/CYCL12 axis in guiding their migration from the primary cancer to the host bone marrow as in the trafficking of the hematopoietic stems and primordial germ cells [54]. The gene discussed is PGR; the disease is cancer.