Using quantitative live cell imaging, genetic analysis, and site of action studies, we have characterized two of these genes: the Rho GTPase cdc-42, which promotes invadopodia formation in a number of cancers; and the Rab GDP dissociation inhibitor gdi-1, a newly identified invadopodia regulator that mediates intracellular membrane trafficking. The gene discussed is CDC42; the disease is cancer.