RAC1 and breast cancer: Additionally, dominant-negative mutants of RhoA (RhoA(N19)), Rac1 (Rac1(N17)) and Cdc42 (Cdc42(N17)) each significantly reduced the number of cells that were found in the blood stream after a subcutaneous injection of MTLn3 breast cancer cells into nude mice compared with wild-type Rho GTPases [55], suggesting that Rho GTPases are not only critical for intravasation, but also for survival in circulation.