 Although both RhoA and RhoC proteins comprise a significant part of the Rho GTPases that are linked to promoting the invasive behavior of breast carcinomas, attributing specific functions to these individual members has been difficult.We have used a stable retroviral RNA interference approach to generate invasive breast carcinoma cells (SUM-159 cells) that lack either RhoA or RhoC expression.Analysis of these cells enabled us to deduce that RhoA impedes and RhoC stimulates invasion.