Since estrogen regulates ANGPT1, 2 expressions in other tissues (Ardelt et al. 2005, Matsuoka-Sakata et al. 2006, Bonagura et al. 2010, Harfouche et al. 2011), we hypothesized that estrogen deficiency may modulate ANGPT2 signaling in the BM niche, triggering ER+ tumor cell awakening from dormancy. Here, ANGPT1 is linked to neoplasm.