RAC1 and breast cancer: The expression of a doxycycline-inducible PAK mutant (T423E) that behaves like normal PAK and retains its ability to bind Rac1 and Cdc42 resulted in a significant increase in the ability of MCF-7 breast cancer cells to grow in an anchorage-independent setting [50], and drove hyperplasia in a mouse mammary gland [51].