We found that BLBCs inhibit activity of the RFC pathway via Cdc42 and that restoring activity of this pathway by genetic or pharmacological inhibition of Cdc42 enables the pro-oxidant activities of low μM concentrations of TMX to be harnessed so as to have multiple beneficial effects on BLBCs, one of the most dangerous categories of breast cancers. Here, CDC42 is linked to breast carcinoma.