TBRG1 and cancer: ATOX1 proximal proteins in myoblasts also include negative regulators of the cell cycle like ERBB receptor feedback inhibitor 1 (ERRFI1) and transforming growth factor beta regulator 1 (TBRG1), both of which inhibit cancer cell growth.36,37 Thus, ATOX1 may play additional undefined roles in regulating proliferation of myoblasts and other cell types.