In the same way, cells transformed by the activated RhoA gene (del Peso et al, 1997) or cells expressing a constitutively active form of RhoA (Yoshioka et al, 1998) have greatly promoted invasive ability, contributing to the acquisition of a metastatic phenotype in vivo. Finally, we recently demonstrated that RhoA activation contributes to breast cancer cell aggressivity (Denoyelle et al, 2003). The gene discussed is RHOA; the disease is breast cancer.