Although a role for nuclear actin in tumor cell growth remains to be established, its involvement is likely when considering the following observations: nuclear actin functions in many aspects of nuclear structure and function [1,13-14], its levels are high in proliferating breast epithelial cells and down-modulated by LN1 [2], and, finally, breast tumors are depleted of LN1 [46] and unable to respond appropriately to homeostatic environmental cues [47]. Here, PHYH is linked to breast neoplasm.