ARHGDIB and breast carcinoma: it is demonstrated that RhoGDI2 inhibited Rac1 activity in MDA-MB-231 human breast cancer cells [13] and mouse embryonic fibroblasts [23], whereas others showed RhoGDI2 acted as a positive regulator of Rac1 in T24 and UMUC3 human bladder cancer cells [14], H9c2 cardiomyoblast cells [17] and ovarian cancer.