To identify Rictor-dependent signaling pathways that contribute to Rac activation in HER2-amplified breast cancers, we examined the impact of Rictor knockdown on the expression of an endogenous inhibitor of Rac activity, Rho guanine nucleotide dissociation inhibitor 2 (RhoGDI2), based on previous observations that Rictor causes RhoGDI2 downregulation in mouse embryonic fibroblasts (MEFs) [22]. This evidence concerns the gene ARHGDIB and breast carcinoma.